From 1961 to 1963, the “senior compact” Pontiac Tempest had a novel powertrain layout featuring a front engine and a rear transaxle, connected with an unusual flexible driveshaft known as the “rope drive.”
Pontiac Advanced Engineering
Along with their individual engineering departments, each of GM’s automotive divisions also had its own advanced engineering section, developing new concepts and new technologies not necessarily intended for any specific production model. The head of advanced engineering for Pontiac during this period was one John Z. DeLorean, who had arrived from Packard in September 1956.
One of the ideas DeLorean explored during the early part of his tenure in Pontiac advanced engineering was the front-engine/rear-transaxle layout. This was a rather trendy idea at the time; Chevrolet and Oldsmobile also studied the concept during this period, although their versions never made it to production.
The interest was probably sparked at least in part by the marvelous Lancia Aurelia. Introduced in 1950 to replace the Lancia Aprilia, the Aurelia was an exceptional car of a kind with no real parallel in the United States. It was by European standards a medium-size family sedan — although Americans would have regarded it as a compact, as it was 2 inches (51 mm) shorter than a 1950 Nash Rambler, albeit on a much longer wheelbase — with a pillarless four-door body (later joined by lovely two-door coupe and convertible variants) and an aluminum V-6 engine, mounted in front and driving a rear-mounted clutch and transaxle through a central driveshaft. Suspension was fully independent (though Lancia eventually switched to a De Dion axle), and static weight distribution with a full tank of fuel was almost precisely 50/50.
By the standards of its era, the Aurelia had superb handling and a firm but comfortable ride, abetted by a commendably robust monocoque structure. Despite modest engine displacement (initially just 1,754 cc (107.1 cu. in.)) and fairly hefty curb weight, the Aurelia also had respectable straight-line performance and decent fuel economy, though with list prices starting at about 1.8 million lire (equivalent to about $3,000 at early-fifties exchange rates, a lot of money in those days), it could hardly be called an economy car.
In any form, the Aurelia was an engineering tour de force, and undoubtedly an object of fascination for automotive designers and engineers around the world. We don’t know for certain that John DeLorean was among its admirers, but we would be very surprised if he were not.
As the Aurelia adeptly demonstrated, there are a variety of advantages to placing engine and transmission at opposite ends of a car. The most obvious is that it shifts a useful chunk of the car’s unladen mass off the front wheels (reducing steering effort and, at least in principle, the tendency to understeer) and onto the drive wheels (improving traction and allowing the rear brakes to do more of the work of stopping the car), without the extreme rear-heaviness that can make a rear-engined car disagreeably twitchy near the limits. Moving the transmission to the rear can also reduce the intrusion of the powertrain into occupants’ foot and knee room. Since the transmission must be fixed in place — which requires the use of independent rear suspension or a De Dion axle — rear unsprung weight is also reduced, improving ride quality and, potentially, handling.
There are also a number of downsides. While a rear-mounted transmission or transaxle may intrude less into cabin space than a conventional RWD drivetrain, it does reduce the rear volume that might otherwise be available for cargo. With a manual transmission, matching revs is more difficult, and the load on the synchronizers is greater because of the added inertia of the driveshaft. Maintaining the correct geometry between engine and transmission can also be challenging, not least during assembly. Additionally, this arrangement is more costly than a conventional live axle layout, and an ill-sorted rear suspension can result in treacherous handling behavior.
DeLorean was certainly aware of these pros and cons, many of which were discussed in a paper he wrote for the Society of Automotive Engineers in 1960. However, as the X-100 project unfolded, he realized that the front-engine/rear-transaxle layout offered something far more compelling: a way to make the Pontiac compact — eventually named “Tempest,” a name Pontiac had applied to its V-8 engines beginning in 1958 — something other than a badge-engineered Corvair.
On paper, the idea was quite simple: Pontiac could keep the Corvair body shell, transaxle, and other mechanical components, but mate them with a conventional front-mounted, water-cooled engine. In that way, the corporation’s desire for commonality would be satisfied, more or less, but a Pontiac salesman would still be able to demonstrate the difference between the Tempest and its Chevrolet cousin by simply popping the hood. All Pontiac would need to pull it off was an engine and a way to connect it to the Corvair transaxle.
From V-8 to Slant Four
At that point in the development process, Pontiac did not have an engine suitable for this application. The division had retired its elderly 239 cu. in. (3,920 cc) six at the end of the 1954 model year. The Pontiac V-8, which for 1959 was expanded to 389 cu. in. (6,372 cc) displacement, was far too much engine for a compact economy car — or for a transaxle designed for a 140 cu. in. (2,287 cc) flat six. There was the new aluminum V-8, but while Pontiac would reluctantly offer that engine as an option, it was too expensive to make standard equipment, something that would also become a problem for Oldsmobile and Buick. As we’ve previously discussed in our article on the 1961–1963 Buick Special/Skylark, Buick eventually solved that problem by creating a cast iron V-6 based on the architecture of the aluminum V-8, but that engine hadn’t even been conceived at this stage, and wouldn’t be available until the 1962 model year. The same was true of the inline six and four Chevrolet would offer for the Chevy II/Nova, a conventionally engineered compact that would supplement (and, as it happened, eventually supplant) the rear-engined Corvair.
Here again DeLorean had an answer: make a four-cylinder engine out of the Pontiac V-8. If this idea seemed somewhat ridiculous, early experiments demonstrated that it could work. Pontiac powertrain engineer Malcolm McKellar found that even with four cylinders disabled, the big V-8 had ample torque and adequate power. By amputating the left cylinder bank, Pontiac would have a 194.5 cu. in. (3,186 cc) slant four that could be built on the existing engine production lines.
It’s easy to second-guess this choice or to point to other alternatives that might have worked better, like a 90-degree V-4 or a de-bored, short-stroke 90-degree V-6. However, Pontiac’s overriding priority was to minimize the tooling investment, and the four-cylinder engine proved the most expedient way to do that. Although the four would need a new crankshaft (still with five main bearings), unique camshaft, and new intake and exhaust manifolds, Pontiac also wanted to share as many existing V-8 components as possible. The resulting “Trophy 4,” as Pontiac eventually dubbed the four-cylinder engine, was bigger and heavier than it needed to be, weighing almost as much as a Chevrolet V-8 of much greater displacement, but it was able to share about 120 parts with the V-8, and its development and tooling were a fraction of the usual cost of launching a new engine.
Cheap, the Trophy 4 was; smooth or refined, it most certainly was not. Any inline four-cylinder engine has a second-order vibration, caused by the unbalanced motion of the reciprocating masses. Even in a relatively small-displacement four, the result is a vertical shaking force of considerable magnitude, which becomes more severe as displacement increases. In a 90-degree V-8 engine, the second-order vibration of one cylinder bank can be balanced against the other through the use of a cross-plane crankshaft and counterweights, but that’s not possible with a slant four, and the bank angle means the second-order vibration has both vertical and horizontal components. With its large displacement and substantial reciprocating mass, the Trophy 4 shook like a paint mixer, and its torsional vibration was strong enough to shred the timing chain it had inherited from the V-8, a problem not fixed until after regular production had already begun.
Today, most passenger car fours displacing more than about 2.2 liters (134 cu. in.) deal with second-order vibration by adding twin counter-rotating balance shafts, but that technology was still underdeveloped in the late fifties and early sixties. (Frederick Lanchester patented the concept back in 1912, but modern balance shaft technology owes a great deal to Mitsubishi, which greatly advanced the state of the art with its “Silent Shaft” fours in the mid-seventies.) In any case, Pontiac didn’t consider balance shafts a possibility for the Tempest due to budget constraints. There was simply no extra money to develop balance shafts, or to modify the block to accommodate them.
Pontiac decided instead to focus instead on isolating the engine, and indeed the entire powertrain, from the body structure, resulting in the Tempest’s most unusual feature, and the one that would earn it its most lasting nickname.
The Rope Drive
Like the other Y-body compacts, the 1961 Pontiac Tempest would use unitized construction, but the suspension and powertrain were carried on detachable front and rear crossmembers. This appears to have been a matter of production convenience rather than an effort to isolate the body structure from noise, vibration, and harshness (NVH). While all suspension and powertrain loads were taken through the crossmembers, the crossmembers themselves were simply bolted to the body, relying on the rubber insulators in the suspension and the drivetrain mounts to limit NVH.
The Trophy 4 engine was supported on the front crossmember by two rubber-isolated engine mounts, one on either side of the block. It was mounted in approximately the same fore-aft position as the V-8 in bigger Pontiac models, albeit offset about 1.4 inches (36 mm) to the left. On cars with manual transmission, the clutch was mounted behind the engine in conventional fashion rather than with the transaxle, probably to simplify the clutch linkage. With automatic, the torque converter was rear-mounted at the back of the transaxle. (Because of this variation, manual transmission cars used shorter driveshafts than did cars with automatic, bolting to the end of a short clutch shaft rather than directly to the engine flywheel.) In back, the transaxle was carried on a differential support arm, attached to the rear crossmember through two more rubber-isolated mounts.
Between the engine and the transaxle was the driveshaft, which rode on two rubber-isolated ball bearing assemblies within a 76.2-inch (1,935-mm) stamped steel torque tube. The driveshaft itself was forged steel, machined, heat-treated, subjected to magnetic particle inspection, and shot-peened to ensure that it was as smooth and straight as possible; it also had a thin protective coating to prevent corrosion and surface wear. Because it only needed to transmit engine torque, not multiplied by the transmission gears (or the torque converter, on automatic transmission cars), the driveshaft could be quite thin. Diameter was 0.75 inches (19.1 mm) on cars with manual transmission, a mere 0.65 inches (16.5 mm) on cars with automatic. Being so thin, the shaft was also flexible, particularly in torsion, able to twist by up to about 30 degrees in either direction.
This flexibility was further demonstrated by the shaft’s unusual designed-in curvature. The driveshaft formed a gentle downward arc, which put the middle of the shaft around 3 inches (75 mm) lower than either end. Contrary to some early press coverage, this had nothing to do with the torque tube bearings. Rather, the curvature was created by the bending moment applied at both ends of the driveshaft by the shaft’s rigid connections to the engine and transaxle, both of which tilted downward by a total of about 11 degrees. This curvature led wags to dub the driveshaft the “rope shaft” or “rope drive.”
Curving the driveshaft in this way was another of DeLorean’s inspirations, an elegant if peculiar solution to a practical problem. Pontiac had found that with a straight driveshaft of such length and small diameter, the shaft would develop strong, destructive vibrations at a critical speed within the normal range of operating speeds. Bending the shaft into an arc shifted the resonant frequency out of the normal operating range, which eliminated the problem (although the driveshaft could still rattle on its bearings under certain conditions). A similar resonant frequency problem with the torque tube was addressed by varying the tube’s cross-sectional area, putting its critical speed below normal engine idle speed and giving the tube a constant bending stiffness throughout its length.
As a bonus, the driveshaft’s curvature also made it possible to minimize the height of the torque tube, reducing its intrusion into cabin space. To achieve a similar result, the Y-body Oldsmobile F-85 and Buick Special needed a costly two-piece driveshaft, with a constant velocity joint in the middle as well as a universal joint at each end.
The torque tube was something of an afterthought. It was not included on early test mules, and was initially added simply to help maintain the correct alignment of the driveshaft relative to the engine and transaxle. However, it emerged as an important part of the concept. Interconnecting the front and rear crossmembers proved to be an invaluable aid to production and assembly, and the torque tube also helped to mask the bad manners of the Trophy 4 engine.
By rigidly connecting the engine and transaxle, the torque tube limited the engine’s range of motion, preventing the big four from moving laterally or fore and aft. Some of the engine’s torsional vibration, meanwhile, was absorbed by the twisting of the driveshaft within the torque tube. That left only the vertical shaking forces caused by the engine’s secondary vibration and by torque reaction from the drive wheels, which were absorbed by the four soft rubber powertrain mounts. (The engine mounts were so soft that Pontiac had to add metal limiters to keep the engine from shifting too far out of its appointed space.) No one would ever accuse the Trophy 4 of silken refinement, but this arrangement proved remarkably effective. There was still a lot of commotion under the hood, but it was largely unnoticeable inside the car, at least so long as the engine and engine mounts were in reasonably good health.
Transaxles and TempesTorque
Although its transaxles had some commonality with the ones used on the Chevrolet Corvair, the manually shifted Tempest parted ways with the Corvair in several respects. In Corvairs with manual transmission, the clutch was mounted behind the differential, sending power forward with a clutch shaft that ran through the center of the hollow pinion shaft and main shaft to a clutch gear at the front of the gearbox. Power then flowed back through the transmission main shaft back to the differential pinion shaft. Since the Tempest mounted its clutch in front, this convoluted power flow was unnecessary; the trailing end of the propeller shaft was simply splined to the clutch gear of the three-speed gearbox, whose main shaft was splined in turn to the differential pinion shaft. The Tempest three-speed also had closer ratios than the Corvair three-speed (the same ratios as the Saginaw three-speed that would become standard on the 1962 Chevrolet II), although first gear was still unsynchronized. The all-synchro Corvair four-speed would be offered later, but wouldn’t be available at launch.
The automatic transaxle, which Pontiac dubbed “TempesTorque,” was more closely based on the Corvair Powerglide, even mounting its torque converter behind the differential, as on the automatic Corvair. In a Corvair Powerglide, two hollow shafts passed through the hollow differential pinion shaft: a central pump shaft that allowed the torque converter impeller to drive the transmission’s front oil pump and a hollow turbine shaft that allowed the torque converter turbine to drive the transmission’s input sun gear. TempesTorque added an internally splined coupling to the leading end of the pump shaft, allowing the flexible driveshaft to drive the pump shaft and thus the impeller of the torque converter. This was circuitous, but it allowed a transmission intended for a rear-mounted engine to take its power input from the opposite end with minimal design changes.
Pontiac used a different torque converter than the Corvair unit, providing a stall ratio of 2.0:1 rather than 2.7:1, and added a nuance not shared with the Corvair: a split-torque high gear. The clutch hub of the TempesTorque transmission’s direct drive clutch was splined to the pump shaft, and thus always rotated at engine speed, without any hydraulic slippage. When the clutch engaged with the 1–2 shift, the low sun gear would also turn at engine speed, while the input sun gear turned at turbine speed. This had the effect of “demultiplying” slippage in the torque converter by about 45 percent in high gear, a partial mechanical lockup that improved fuel economy and engine response in top-gear cruising. (You’ll find a further discussion of this principle in our article on split-torque transmissions and lock-up clutches.)
One unfortunate similarity between TempesTorque and the Corvair Powerglide was that it had no “Park” position, leaving the selector with only four positions: RNDL. This was a cost-saving measure, but it would later become a source of customer complaints, since the mechanical parking brake’s ability to hold the car on a steep grade left something to be desired. (A parking pawl was belatedly added to the Tempest automatic for 1963.)
While Chevrolet originally hoped to make Powerglide standard on the Corvair, we haven’t seen any indication that Pontiac contemplated a similar strategy for the Tempest. However, such a move would have made sense — the automatic imposed surprisingly little penalty in performance and fuel economy. The torque converter further ameliorated the effects of engine vibration, and also masked the twisting of the driveshaft, which was noticeable and occasionally disconcerting with a manual gearbox and conventional clutch.
The Y-Body Tempest
By mid-1959, GM corporate management had accepted the new direction for the Pontiac compact. The corporation also authorized Pontiac to adopt the longer Y-body shell. We assume that with Pontiac no longer sharing the Corvair mechanical package, the priority had shifted to recouping the tooling costs of the bigger body, since it was likely that the cheaper Corvair, then nearing the start of regular production, would handily outsell its B-O-P cousins (as indeed it did).
This meant that Pontiac’s focus now shifted from differentiating their compact from the Corvair to differentiating the Tempest from the Buick and Oldsmobile Y-bodies, the Buick Special and Oldsmobile F-85. Pontiac arrived quite late to that particular party, and had to contend with a stylistically inflexible unitized body shell whose basic dimensions had been largely dictated by Buick and whose styling had been tailored to suit Oldsmobile.
Fortunately, Pontiac had a readily identifiable styling feature that could be made to work within the limited tooling budget: the “hairpin” split grille, developed by previous Pontiac styling chief Joe Schemansky for the 1959 Pontiac line. Although the 1960 Pontiac line, mostly done when Humbert arrived, had gone a different direction, Humbert revived the theme for the 1961 models, correctly recognizing that it gave Pontiac an immediately recognizable “face.” The Tempest eventually adopted a variation on the 1959 theme, which reduced but could not wholly eliminate the inevitable resemblance to the Special and F-85.
To the likely dismay of the sales executives and accountants, the biggest tooling change Pontiac made to the Y-body shell was one most customers would never see: a new floorpan to accommodate the torque tube. This didn’t even provide a completely flat floor, which might have given the Tempest a unique selling point. It did at least lower the driveshaft hump to roughly ankle height, and the floor was flat in the area around the front passenger’s feet, which helped to justify subsequent advertising claims of six-passenger capacity — or would have, had Pontiac not decided that every Tempest with manual transmission should have a floor-mounted shifter. (As on the Corvair, the selector for the automatic was neatly integrated into the dashboard, again making us wonder if Pontiac originally intended to make TempesTorque standard equipment on the Tempest.)
Floor shifter or no, the Tempest’s potential sportiness was undercut by the decision to launch with only four-door sedan and four-door Safari wagon body styles — not exactly a pulse-quickening lineup — and bench seats. The Tempest wasn’t a bad-looking car, but as yet, there wasn’t much of the design pizzazz that would become a Pontiac hallmark throughout the sixties.
36 CommentsAdd a Comment
Good job on the airplane ID- indeed an Aero Commander, I believe a ‘500U’ model, the ancestor to the later ‘Shrike’ made famous by R.A. ‘Bob’ Hoover.
Thanks for a very informative and well researched read! Good years for aviation and autos…
Another good job, up to your usual standards.
As you point out, the Corvair Monza sold much better than the base model. It’s more or less a truism that the upgrades would have been more profitable than the basic car. With the stipulation that hindsight is 20/20, Chevrolet could have taken a lesson from the nicely trimmed Nash Rambler.
If I didn’t already know that Vauxhall was a subsidiary of an American automaker, the Victor’s styling would lead me to suspect it.
Deciding how to position a car in terms of base price is complicated, and I don’t want to be TOO dismissive of that. It’s clear that base price can function as a psychological barrier, and it’s not a stretch to concede that the same 1960 compact buyer willing to add $299 worth of options to a $2,000 car might have dismissed as too expensive a similarly equipped version of the same car listing for $2,300. Also, Chevrolet did sell a fair number of base-trim Corvairs (around 63,000 for 1960), and I’m sure there were sales execs who argued that standardizing a better-equipped trim level would have meant throwing those sales away. The corporate priority was maximizing return on tooling investment, which generally meant maximizing production volume. Selling 300,000+ cars a year paid off the tooling costs far more quickly than building “only” 200,000 of a pricier better-trimmed version. The problem, of course, was knowing where to draw the line so that the price-leader base model didn’t become seriously deficient. For instance, I think it was probably reasonable to sacrifice the original plan to make Powerglide standard, but both the Corvair and Tempest should have had the ’64 Corvair suspension from the outset, even on base models.
(One point the Tempest story highlights is that just the front anti-roll bar was not enough. The Tempest got that much sooner than the Corvair did — as a running change for 1961 — and it didn’t help all that much. I suspect also adding a transverse leaf spring would have helped, although perhaps not quite as much as on the Corvair. Part of the issue with the Corvair was that its rear springs had to be stiffer to support the powertrain, which was less of an issue with the rope-drive Tempest, although the transverse spring might still have helped to reign in the camber change antics.)
Another quality article,Aaron.The Tempest was definitely a fascinating design, second only to the Corvair in ingenuity in that era.By the way, International Harvester also used a Half-a-V8 design in the Scout, a contemporary of the original Tempest. It had a much longer production run.
The International Harvester 4 had a displacement of 152 cubic inches, in the same ballpark as GM’s Iron Duke. Presumably it wouldn’t have been very refined, but it would have been more refined than the Trophy 4. In that application a high degree of refinement probably wasn’t expected.
I’m not very familiar with IHC engines, but the brochures I could find say the seventies “Comanche 196” engine displaced 195.4 cu. in. (3,203 cc), which was a bit bigger than the Trophy 4 and probably about as rough.
I wasn’t aware of that one. I’m pretty sure they had a 152 CID I4 also.
Yes, there was a smaller “Comanche Four” that was first introduced for 1961. It was based on the V-304 and shared its bore and stroke, giving 151.8 cubic inches (2,488). The “Comanche 196” followed in 1968, based on the V-392.
I found I had a Car Life review of the 1961 Scout with the 152, whose refinement they characterize only as “smoother than you might expect” — not very revealing in this case, and not an especially high bar. They note the conceptual similarity to the Pontiac Trophy 4, but unfortunately offer no detailed comparison, which might have been interesting.
That 4-cylinder Scout engine could also be had with a turbocharger, although I think it was more aimed at high-altitude areas like the Rocky Mountain states than just extra power.
I read a little bit about that the other day. Apparently, the turbo package, which made 111 hp (compared to 93 hp for the normally aspirated four) was expensive and not terribly well-sorted, and was fairly rare. It expired not long after the bigger 196 cu. in. four became available, although it was still listed as an option into 1968. (The 1968 Scout brochure lists normally aspirated and turbo 152 and normally aspirated 196.)
I have a 1962 version of the Tempest service manual that I picked up at the swap meet in Carlisle (PA) many years ago. I hoped to own one some day after reading “Unsafe At Any Speed” and seeing the quote from Road Test magazine printed in late 1964 to describe the new for 1965 Corvair with the proper independent rear end. It said (speaking of the 2nd gen Corvair), “Previous to 1965. the car was probably the worst riding, worst all-around handling car available to the American public with the exception of the original Pontiac Tempest.” So one can infer that the Tempest was – at the time – THE worst riding, THE worst handling car available – at any price – in North America, at least according to the authors of that article. Reading that made me really want a Tempest – to celebrate it as the worst of the worst in every automobile attribute you can define and quantify. How awesome.
To describe this car as a magnificent kludge is accurate when you read the proper procedure for setting rear wheel toe alignment. On the 1961-1962 models, the service manual says you adjust the toe angle by using shims on the rear swing arm mounting points to slightly change their angle (as viewed from above) from the roughly 40 degrees to a little more or less. Each wheel can be adjusted independently. With the hubs bolted to those arms, changing their angle changes the rear wheel toe – in or out. But doing so also moves the transaxle slightly in a longitudinal direction. And remember that the engine is rigidly fixed to the transaxle via the torque tube. So in comes the kludge part of the procedure: Before adding or removing shims to adjust rear toe, the manual says you should loosen the motor mounts, add/remove shims to get the toe set properly, then run the engine for a few minutes to allow the engine to settle into proper position after being moved forward or rearward within the car, then shut down and tighten the engine mounts. That sounds like a “gee we never thought of that” workaround, doesn’t it?
Thank you for covering this unique moment in automotive history. It reminds me so much of those cooking shows that give three or four teams and handful of ingredients and challenge them to make a gourmet meal from what they are given. In the case of the Tempest, they got the Olds/Buick body, a Buick V8, half of a Pontiac V8, and a Corvair rear suspension and transaxle. And from that, they prepared the best they could within the budget and time limitations.
Since you’re moving the engine forward or backward, how much force do you have to bring to bear on the shims?
The torque specs in shop manual were nothing particularly extreme. It seems that the specific issue was that the engine mounts were VERY soft and allowed a lot of deflection, making it easy to inadvertently misalign the whole powertrain.
The revised 1963 suspension simplified rear toe adjustments (toe was adjusted by shimming the mounting bracket on the leading end of the control arm, rather than the differential mounts), but the 1963 shop manual still recommended loosening the engine mount bolts first and then retightening them afterward, I assume for the same reason.
Incidentally, the 1961 and 1962 shop manuals recommended inspecting rear toe and adjusting as needed every 2,000 miles, so this was not an infrequent chore if you followed the manual!
Thanks for another great article, Aaron! I enjoy reading about unusual designs and what led to those decisions.
Is there any info on how the rope drive fared in service? I’ve wondered how the continued flex and torque would affect the metal over time or if the support bearings life was affected.
The Pontiac engineers who developed the Tempest said the early cars suffered problems with the engine timing gear basically shaking itself to bits, since the V-8 timing gear and timing chain wasn’t designed for the greater shaking forces of the four-cylinder engine, and a contemporary owners’ survey found a surprising number of owners (around 30 percent) complaining of problems with the manual clutch. Those seem to have been the major initial reliability issues.
It seems that at least within the cars’ original design lifetime, the flexible driveshaft itself worked out pretty well. I don’t know what the fatigue life of the shaft ended up being in practice; I couldn’t find any detailed information on that, so I can only speculate based on the design parameters. Pontiac did try to over-engineer the driveshaft to avoid fatigue problems (heat-treated shot-peened forged steel, which was very expensive), and the bending moment is supposed to remain constant throughout the shaft, so I don’t know that the curvature would affect the shaft’s fatigue life that much. However, I do have to wonder about the torsional forces involved. The shaft was designed to twist through a range of about 60 degrees (30 degree in each direction), which seems like it would eventually take a toll, both on the shaft and on the protective coating applied to its surface.
As for the torque tube bearings, their main function appears to have been to support the shaft in the tube, and the shop manual asserts that they were sealed for life, so it appears Pontiac assumed their operating stresses would be fairly low. The shop manual doesn’t list any procedure for inspecting or replacing them in service, although I have to wonder what happened when they got old and the rubber and plastic insulators within each bearing assembly started to get crunchy. A more immediate concern may have been the longevity of the torque tube itself, particularly in areas that used a lot of road salt. I assume the driveshaft’s protective coating was intended to prevent corrosion, but the torque tube was just stamped steel, and so moisture inside the tube or bad surface rust, especially around the bearing mounts, seems like a potentially nasty problem on an older car.
Again, I don’t have any hard data or first-hand experience to share in these regards, and I’m definitely NOT a mechanic, but those are the areas of the design that seem like obvious areas of concern.
So good to see this superb article finished and posted. Extremely thorough and lots details and context.
A couple of minor things or questions: That ’61 LeMans coupe without any exterior bright trim threw me. It went against everything I knew and remembered about the LeMans, a package of trim and other features comparable to the Monza. I can’t imagine a “stripped” one being offered. I went to the 1961 Tempest brochure, and in the text for the LeMans, it says “Full custom treatment on hardware and trim – all standard!” I very strongly suspect that the pictured LeMans in your post was either de-trimmed for some reason, custom-ordered, or maybe it was base Tempest that someone add the LeMans badges to? Whatever; it’s a pretty minor detail.
Like you, I thought the ’63 restyle was not successful, in its attempt to make these cars look bigger, undoubtedly to transition them to the larger A body for ’64. And yes, the ’62 front end is not very good either.
You summed it up perfectly in your title; this was a classic kludge. I understand what DeLorean was trying to do, and appreciate the limitations they had, but the result is both fascinating yet unsatisfying on a number of levels.
Our next door neighbor in Iowa City bought a new ’62 LeMans convertible; she was a single, Russian middle-aged professor of Russian at the university. One could say she was perhaps a representative target demographic? The sound of that big four was deeply imprinted on me at that age, not in a very good way, but I did have a memorable ride in it once, with the top down. That rather masked the sound of the engine!
If you mean the blue Le Mans with the white roof (which is a ’62), I don’t know its provenance, so I can only speculate. This is also complicated by the fact that the 1961–1963 brochures I could find did not have any detailed specifications for the Le Mans, which leaves some question about how much of the chrome trim was standard. The Custom included some but not all of the optional brightwork, and my guess would be that at least some of the chrome gewgaws (e.g., the fuel door filler trim) was probably still optional with the Le Mans package. It’s also possible that the owner didn’t like some of the chrome bits, or, perhaps more plausibly, had lost or damaged the trim on one side, couldn’t find a full set of replacement trim, and decided to remove the rest so it would at least be symmetrical. It would not be a base coupe with Le Mans badges (since I believe the base coupes came only with the now very rare standard coupe roofline rather than as “Sport Coupes”), although it might be a Custom coupe with Le Mans badges. Short of asking the owner, I don’t know.
The ’63 restyling/enlargement was apparently proposed by Pontiac quite early, I believe before the decision about what to do for ’64 had been made. So, I think it wasn’t so much a transition to the bigger ’64s as a response to B-O-P managers fretting that the ’61 senior compacts looked too dinky, even with 4 inches more wheelbase than a Corvair. That said, it did end up serving as a transition to the ’64 Tempest/Le Mans, which I think had better proportions.
A Happy New Year, and thanks for another great article.
It’s quite fascinating that the “compact” car of the past in North America are considered big cars elsewhere, including places that are said to have similar taste to America, like Australia (Even the largest Falcons of the 70s are smaller than the Mavericks at that time). Pretty sure the Tempest is similar.
Yes, that’s been a recurring theme. The 1961–62 Tempest was 189.3 inches (4,808 mm) on a 112-inch wheelbase and 72.2 inches (1,834 mm) wide, weighing around 3,000 lb (1,360 kg) with the four-cylinder engine and automatic, so it was not a particularly small car on a global scale. For instance, it was 21 inches longer and 9.7 inches wider than a Mk1 Ford Cortina, and about half a ton heavier. (The Tempest was the heaviest of the Buick-Oldsmobile-Pontiac Y-body “senior compacts” with the four-cylinder engine; the Buick aluminum V-8 and cast iron V-6 were a good deal lighter.)
Aaron, thank you for this interesting article on the rope=drive Pontiacs. I owned GTOs and Le Manses in my younger days (Along with a Catalina) and counted myself as a Pontiac afficianado, and I also very much liked the BOP Y bodies (especially the turbocharched Cutlass), but never owned one.
Most of us who enjoy cars are familiar with the Corvair swing axle issues, and in this article you have added good teaching about what was and was not inherited by Y body Tempests which used the Corvair derived transaxle. I especially appreciated your description of automatic transmission differences from the Corvair version, and also your discussions regarding the “rope” itself.
But (there’s always at least one, isn’t there?) while I recognize that the subject and purpose of your article was to discuss Y body Pontiacs, I’ve always had questions regarding these cars and Corvairs. I understand the issue about roll centers, camber changes, and sudden oversteer. What I do not understand is why the same design was used by Volkswagen (also a “cheap” car), Porsche (not a cheap car and noted for its handling), and Mercedes Benz cars from the 50s to the 70s, and similar Jill Claybrook-inspired handwaving and pearl-clutching hasn’t accompanied those autos?
(By the way, I believe Ford used a similar sort of idea in their “Twin I Beam” 4 wheel drive front axles in their pickups, where the lengthened arms were intended to counter camber changes, with middling results.)
I think I understand that Mecedes Benz used a lower center pivot point for their swing axle and incorporated some sort of monkey motion to make the swing axle behave in an intermediate way between a fully independent system and a live axle with regard to camber change.
I wonder if your story of Rudi Uhlenhaut testing and commenting on the Tempest had something to do with the Mercedes Benz implementation of the swing axle?
I also think that Porsche used an anti-roll bar on the rear swing axles of some of their models, but I’m not so sure about this.
Did the DeLorean patents have something to do with designing some Mercedes Benz-like trickery to the Tempest suspension?
If it is convenient for you to shed a little light on this question (Corvair and Y body Tempest versus Mercedes Benz, Volkswagen, and Porsche swing axles), I would very much appreciate your comments.
Another thing you’ve done with this article is add more fuel to my mental exercises regarding John Z DeLorean. I’ve always liked the Pontiac OHC 6 (aand still do!) and your discussion of his Packard Ultramatic are very interesting. Now you’ve added the rope drive and the slicing of the Pontiac V8, a la Sesco midget engine, to the whole John Z DeLorean story, along with his rebellious GM leadership years, the DMC episode, and also his cocaine sales sideline. He was clearly a complex man with talent, taste, and a tug-of-war between ambition and ethics. I don’t say this from a judgmental perspecive, but rather a contemplation of the human nature we all share.
Volkswagen DID; the Beetle got its share of negative ink in Unsafe at Any Speed for that reason. Mercedes-Benz, meanwhile, mitigated the worst of it with the low-pivot axle. The original gull-wing 300SL, which didn’t have it, is still notorious for its unforgiving swing-axle characteristics, although there were so few of the coupes and seeing one was and is such a rare event that it’s just kind of part of the lore. The low-pivot axle used on the 190SL, the W113 cars, and most of the sedans and coupes, lowers the roll center, reduces the tendency to jacking (which is an angularity issue), and limits rear roll stiffness. It’s still not ideal geometrically, but it’s less likely to be treacherous.
As for Porsche, the rear-engined air-cooled cars’ penchant for tail-swinging was well-known, evidenced by years of reviews insisting that the latest suspension revisions had definitely finally, truly put to rest the nasty oversteering antics, while assuring the ego-sensitive reader that those antics were never really a problem for someone who Knows What They’re Doing, that eternal shibboleth of automotive apologism. I will grant that with a 356, (a) their reputation for oversteer certainly preceded them, and (b) they were sports cars, with quick steering and sharper reflexes, so you could potentially manage the tail’s periodic excursions from linearity without necessarily going around in circles or wrapping the car around a pole. (The air-cooled 911 had semi-trailing arms in back and wasn’t quite the same animal, although semi-trailing arms have sharpish trailing-throttle characteristics even with a forward weight bias.)
The dilemma with the Tempest, as with the Corvair, is that its chassis was trying hard to be conventional American family car: soft springs, soft shocks, slow steering, and rear suspension geometry compromised by the expectation that people would really want to use it to carry six passengers. So, there was little immediate indication that it would handle differently than other cars of its size and vintage (most of which did not, it should be said, handle very well either). If you tripped over the line, it was hard to catch and the suspension and steering were not very cooperative.
This is the point of the Uhlenhaut anecdote. He was obviously showing off — it was part of a Mercedes launch demonstration — and I assume he intended to put the tail out, presumably to contrast its behavior with the better-mannered low-pivot Mercedes rear axle. However, even with advanced planning and a high level of skill, he overcooked it, memorably alarming people who witnessed it.
The Mercedes low-pivot axle would not have translated directly to the Tempest for a number of reasons, particularly the rigid interconnection between the transaxle and the engine. DeLorean came up with two alternatives: The first carried each rear wheel on a big, wide lower A-arm, hinged at the bottom of the differential; each swing axle only had a single inboard U-joint, but had a telescoping section allowing it to change length as the wheel moved from jounce to rebound, providing a longer swing arm length and lower roll center. The second, which he actually called a “simulated low pivot swing axle suspension,” also specified telescoping U-joints, but had no lower control arm, just a transverse leaf spring bolted to the underside of the differential, serving as both control arm and spring. How well these would have worked in practice is hard to say — I’m not sure if they were ever even built — but they were designed to achieve similar effects as the Mercedes low-pivot axle, albeit not in the same ways.
The Tempest would probably have benefited from some of the fixes Chevrolet eventually offered for the Corvair. There was initially a H-D kit for the Corvair that included stiffer but lower coil springs that effectively decambered the rear suspension, along with a front anti-roll bar (which the Tempest had by the end of 1961) and limiter straps for the rear swing axles, as a crude way of limiting tuck-under. The ’64 Corvair had softer rear coils with a transverse leaf spring between the rear trailing arms, pivoted off the bottom of the differential, so it would support the rear end vertically and resist tuck-under without adding to rear roll stiffness. It wasn’t as elaborate as the completely new three-link suspension for ’65, but it helped. Unfortunately, Pontiac didn’t offer anything like that, so it would have been a matter of trying to find aftermarket or homemade solutions.
As far as I know, early swing axle suspensions didn’t use rear anti-roll bars, since the high roll center and stiff rear springs provided more than enough rear roll stiffness. Some later Porsche rear-engine models did, but as mentioned, the 911 had semi-trailing arms, not swing axles.
Thank you, Aaron! This makes a lot more sense than what I possessed on the subject.
Would it be correct to say that the Corvair’s, Volkwagen’s, and Porsche’s oversteer habits were exacerbated beyond swing axle issues with the engine hanging from behind the rear axle? It would seem that having that weight out at the end of the car would want to bring the rear around when the car got out of shape.
Regarding Mercedes Benz and Uhlenhaut, I am not dismissive of their technology, as they certainly have a long and enviable record of innovation, development, and quality. However, I try to always apply a degree of skepticism regarding matters that seem to fall under commonly accepted truth/myth. When I was young, I recall going to the Chicago Auto Show with a friend (this would have been in the early to mid 70s, when Pontiac Firebirds had big chickens on their hoods). Stopping at the Mercedes Benz display and having been inculcated with machines like the 300SLR with desmodromic valves and the W196, I saw a display of their high tech carburetor, which was such an obvious rip off of GM’s Quadrajet (a carburetor that I did and still do hold in low esteem) shocked me with its near total resemblance. The Rochester carburetor book by Bill Fisher and Doug Roe even has a cutaway diagram of the Solex carburetor Mercedes Benz used in those years and notes this resemblance on page 122. I recall the representative giving me a very condescending look, which did nothing in my mind to dissuade me from the opinion that he was a snob, and snobby as only an ignorant person can be.
Returning to the Pontiac, it seems that this is yet one more of many issues from Detroit where the “what ifs” can be tracked back to money. As much as I hate to admit it, when it came to compacts, McNamara had the right idea with the Falcon and, as you rightly pointed out, Ford’s artistry with cast iron. The technology in that case really did have a direct and positive effect on what the customer bought, even if it wasn’t understood or even known.
Your noting the popularity of the Le Mans and Monza packages shows that the public wasn’t completely turned off by the smaller car if it was marketed correctly. Cosworth Vegas and Fieros had promise, as did even the Pontiac OHC 6, but all of these cars didn’t have what Toyotas et al had. This is a pretty recurrent story, I suppose: as you allude to, even Rover and TVR could take the Buick 215 and make it into something good (not to mention Repco!) that Detroit always seemed to miss.
My object in mentioning Uhlenhaut specifically was not to say, “Mercedes-Benz good, Pontiac bad,” but rather, “Even in the hands of an expert driver, the Tempest’s handling characteristics could be a handful.” (I don’t think any reasonable person would disagree that Rudi Uhlenhaut Knew What He Was Doing behind the wheel of an automobile.)
I’m sympathetic to people who bristle at the accusation that a relatively cheap American car is technologically inferior to a European car costing vastly more money (a Mercedes 220SE cost very nearly $3,000 more than a 1961 Tempest, and a Lancia Flaminia sedan was getting on to three times the Tempest’s base price). On the other hand, even Chevrolet made more of an effort to address the handling flaws of the swing-axle Corvair, and there was no particular reason Pontiac couldn’t have done the same. (The 1962–63 Corvair handling kit wasn’t standard because the decambering of the shorter springs wasn’t desirable for carrying a full load of passengers; the 1964 compensating spring didn’t have that issue, although decambering would have further improved handling.)
As for the question of whether the location of the engine made a difference, the answer is, “Yes and no.” Putting the mass of the engine behind the rear axle is obviously going to shift the longitudinal center of gravity rearward, and means that once the tail cuts loose, it will have more inertia. Furthermore, the rear springs will tend to be stiffer because they have to support the weight of the engine, although this can be mitigated by using a compensating spring that is arranged so it doesn’t contribute to roll stiffness. On the other hand, a lot of the problems with swing axles come down to unfavorable geometry, exacerbated on the Tempest and early Corvair by static positive camber.
Jerry Titus, who had written a cogent dissection of the Corvair’s handling problems in the last issue of a short-lived magazine called Foreign Cars Illustrated (reprinted in the Brooklands Corvair road test portfolio), wrote a followup in Sports Car Graphic, where he reported that the Corvair’s cornering power actually improved by about 20% by adding 170 lb of weights on the floor of the back seat. The reason was that this more closely replicated the original design parameters for the suspension: The expectation was that the Corvair and Tempest would be used as family sedans, and with such a short swing arm length, that meant the static camber had to be positive so that adding weight in the rear wouldn’t produce excessive negative camber and high tire wear. Adding weight eliminated the positive camber, letting the rear wheels get a better bite on the pavement, and changed the angles of the halfshafts relative to the U-joints so that jacking was less likely. This is an area where the Porsche 356 was starting with an advantage; Porsche had not set up the suspension with the expectation that it would carry six passengers!
The dilemma that all the domestic automakers ended up facing in the early sixties was that the market for which they had designed the compacts was not really the one they ended up with. The initial Ford Falcon was pretty much what dealers had been screaming for in 1957: It was cheap, it was thrifty, it was uncomplicated, and it didn’t scare the horses. The idea that people would want to pay extra (and, on a percentage basis, a bunch extra) for junior Thunderbirds was not really on the table at the outset, and it seems Detroit was pretty well flummoxed by it. People did still buy the cheaper base cars, and at a rate that I think would have made the divisions very reluctant to push the base prices too high, but the take-up for the deluxe editions was really unexpectedly good. I don’t think it was a matter of “marketing them right” so much as the buying public having turned out to want something different that happened to be more plush. (By contrast, I don’t know that the Monza, Futura, et al would have gone over terribly well if the cars had been launched that way just a couple of years earlier — look at what happened when Chrysler brought out the K-car in the early eighties, where the early cars were optioned up at a time where people wanted basic and cheap.)
The aluminum V-8 is another matter. Producing the engine early on really proved to be kind of a nightmare. Buick used semi-permanent molds (metal exterior molds with sand cores for the internal passages), which turned out to be much more expensive than anticipated, took too long, and had various areas where things could and did go wrong, resulting in excessive porosity and/or machining chips that weren’t completely cleaned out of the castings. Rover didn’t have anyone who could replicate the semi-permanent mold process, so they redesigned the block so that it could be sand cast, with pressed-in cylinder liners rather than the cast-in liners of the original. They also benefited from a great deal of technical assistance from Buick, which was happy to share their experience with production and service issues, and from Joe Turlay, the Buick motor engineer who had designed the engine (from original Engineering Staff concepts).
Keep in mind also that from Buick’s perspective, they hadn’t abandoned the small V-8 so much as developed it into a series of far less troublesome, much cheaper, and still quite light cast iron engines. The 90-degree V-6 in 225 cubic inch form was still under 400 lb (with all accessories, minus flywheel) and just as powerful as the aluminum 215, if not as smooth. The iron 300/340 V-8 didn’t have any smoothness worries and only weighed about as much as a Ford 289, also one of the lightest V-8s in the industry. So, Buick felt they’d made a couple of silk purses out of a sow’s ear, and, according to Rover and BL engineers, were somewhat incredulous and at least a little amused that BL was still interested in the old aluminum version.
As I’ve said elsewhere, I’m not convinced the Y-body Tempest had any abundance of untapped potential. Giving it a camber compensating spring à la ’64 Corvair would have made it more agreeable without any dire compromises, and a decambered “performance suspension” and faster-ratio steering for a few extra bucks might have made it a bit more agile, but the A-body Tempest/Le Mans/GTO was where the market was going, and the rope-drive powertrain was not readily compatible with that.
Aaron, you bring up a number of interesting topics, which I find useful and educational!
1. The Buick (BOP) Aluminum 215: All I had understood about these engines was that there were many service issues connected with people not using antifreeze in the aluminum block and the resulting corrosion causing a great deal of trouble. I did not know that a sort of die casting technique for casting these engines was used, or that the British went to a full sand casting process to make them. Nor did I know that Buick engineers lent some engineering assistance to them for adapting this motor to British use.
The engineering needed for making aluminum things was not foreign to the British or to the USA: plenty of aircraft engines were made by both nations during the War, and some small amount of expertise would have resided with outboard motor manufacturers at the time.
As I recall, Chrysler tried to make a Slant 6 out of aluminum at this same time, which was also abandoned. I’ve read that modern hot rodders have sought out these aluminum Slant 6s and have experienced issues with warping, and I wonder if this is why Chrysler gave them up, as well.
2. Yes, Buick did develop two forks from the 215: the V6, which they ended up having to get back from Jeep. The V6, with some development, did go on to enjoy some respectable power output in stock form in the Buick Grand Nationals. The other fork, as you said, went into making the engine out of thin iron and increasing its size to 300, 340, and 350 cu in. I believe the first or all of the 300s retained aluminum cylinder heads.
The bore spacing of the original engines didn’t allow a 4″ bore, so by the time these V8s got to 350 inches, they had long strokes. None of these engines had great heads, and they had cast rods, so in my youth I scorned them. I preferred the Olds low deck V8 (330, 350, and much later 403) which didn’t have great heads either, but they did have forged rods. (You’ll undoubtedly note my hypocrisy here, being a Pontiac man in my youth!)
Cadillac, too, went to cast iron wonders (block, heads, crank, rods) and today we even have sintered rods with break cap joints on the big ends from the factory (like a McCulloch chainsaw, of all things!) and all of this stuff works OK. Maybe the commentary that can be made here is that Detroit often did not stick with their engineering and development, not only with making aluminum engines, but with high silicon bore finishes (Vega), converting gasoline to diesel engines (the Olds 350 – it was doable as GM had done with the GMC V6, but they didn’t do their developmental homework), the Cadillac wet sleeve 4.1 and 4.5 V8, and a host of other technologies.
I’ve understood that Ford was traditionally the most conservative maker. They stuck with cast iron. Old timers have told me that, in the Model T days, Ford bolts were legendary for their hardness — a result of Henry’s vanadium, I assume. Henry’s foundry technique was good, even making serviceable crankshafts for the V8 when everyone else used a more expensive forging process. It’s no surprise that Ford would lead the way in thinwall casting back at the beginning of the 60s, first with the 144 six, and then with the 221 V8. This was much cheaper than aluminum and apparently avoiding terra incognita engineering-wise was a profitable decision. Buick, as you said, followed and Olds wasn’t far behind with the thin cast 330 in ’64 and the 425 in 65. I don’t claim that those first Falcons were wonder cars (I’m certainly no admirer of McNamara, either as a proponent of daylight precision bombing winning the war, as a bean counter, or other things), but he did provide a serviceable product at a reasonable price in the Falcon. Iacocca dressed this car up in the ultimate dress-up job, the Mustang, and Ford found this to be very profitable indeed.
2. I do bristle at the idea of Europeans knocking American engineering, but also at the not-invented-here attitude of many Americans (of which I was formerly one). Back in the 60s and early 70s, my impression was that some European cars were of high quality, but also that some American cars were pretty well designed and assembled, too. The price difference you mention did provide a value, but some 60s-era American iron offered quite a bit of “bang for the buck,” as well. But perhaps the issue is moot. Detroit is hardly in the car business anymore. Apparently, the only place USA makers can find refuge from the world is from behind LBJ’s “Chicken Law” of 1965. Beyond the pale of that, profitability seems elusive for them.
Thanks for the suspension discussion. Porsche did seem to make the rear engine layout work pretty well.
You mention the Y body Tempest’s potential, and I think that you are right. Americans wanted cheap cars during the Eisenhower recession but soon forgot that in a few years, and Detroit followed suit. (The A bodies and the Mustang are great examples of this.) It’s a shame that the concepts of rear engine, front engine/rear transmission, and a host of other innovations weren’t appreciated by the public. I think, for instance, of the switch pitch feature in TH400s and front wheel drive were discontinued as a cost saving measure, since the public didn’t appreciate its value. So many of these technologies were rediscovered and reapplied in our modern era. If we cannot blame Detroit for following the market rather than a “better” technology direction, should they be let off the hook for losing a great deal of their market share by sticking with their bean-counter mentality in the 70s and the 80s?
Yes, both Chrysler and AMC offered sixes with aluminum blocks. AMC offered one for the 196 from 1961 to 1964, Chrysler on 1961–1963 225s. Unlike the Buick engine, both AMC and Chrysler had die-cast blocks with iron heads. Neither worked out well. The blocks had open decks, and the loads on the cylinder walls and on the head gaskets were quite high. Because iron and aluminum have different expansion rates, overheating can be very troublesome with an iron/aluminum engine (either aluminum heads on an iron block or iron heads on an aluminum block), potentially leading to permanent damage. There may also have been coolant compatibility issues.
I think the bigger problem was that the blocks were a lot more expensive than iron and provided no particular benefit other than reduced weight (on the order of 70 lb), so the cost-benefit ratio wasn’t great and the blocks tended to be more fragile than the iron equivalents.
There were several major issues. First, the early aluminum castings ended up having issues with excessive porosity, despite Buick giving them up to three rounds of sealant. Second, there were, as I mentioned, problems with cleaning the castings completely to remove small chips of metal. (One downside with semi-permanent mold castings is that holes generally have to be drilled rather than cast, which I assume didn’t help.) Third, certain types of antifreeze would strip off the top layers of the aluminum. I would surmise that it was probably worse with castings that came through too porous, since that would presumably accelerate the process. The water in the coolant would then cause the little bits of aluminum to corrode, which was accelerated by the copper in the radiator core. Result: a horrible mess. Worse, Buick and Olds didn’t initially know which antifreeze brands would cause the scrubbing effect, so they had to do a lot of trial and error to figure out what to recommend to owners and dealers. These problems weren’t unsolvable — obviously, aluminum engines are now very common — but the learning curve was steep, painful, and expensive.
Semi-permanent mold casting is not die casting. With die casting, you have metal molds into which molten metal is forced at very high pressure (8,000 to 10,000 psi). This is very expensive to set up because the die assembly has to be enormous. (The one Chrysler used for its aluminum Slant Six blocks weighed 22 tons!) Semi-permanent molds use a combination of reusable metal molds and non-reusable sand cores; the metal molds are closed hydraulically for casting, but it doesn’t require the same extremes of pressure. In theory, die casting is more precise and has fewer problems with cleaning, but it’s also more expensive and has its own learning curves.
With the Rover 3.5, the conversion for sand casting made the engine somewhat heavier — not a lot, I think something on the order of 25 or 30 lb — but it was expedient, cheaper, and ended up being less troublesome. Rover also had both extensive engineering notes and Joe Turlay himself to share what had gone wrong with the early engines and how to fix or avoid those issues. For instance, I don’t think Rover had to reinvent the wheel with regard to coolant, whereas Buick and Oldsmobile had had to run whole banks of test engines while arguing with different antifreeze vendors to figure out which formulations would cause scrubbing.
Only in 1964. The 1965 300 had iron heads.
The 215 was designed for the Y-body cars, so compactness and light weight were major priorities. (It was originally supposed to be only 180 cubic inches (3.0 liters rather than 3.5), with the idea that they could offer a bigger-displacement version later as a step-up option, but there were concerns about torque.) The bore spacing was one result of that. As for the head design, it ended up being one of the reasons the V-6 had such a long life: The slanted saucer combustion chamber (which was largely Turlay’s work, since the Engineering Staff design had the entire chamber in the top of the piston) turned out to be effective in reducing hydrocarbon emissions. Oldsmobile was initially dubious about that design, so the Olds 215 heads have wedge combustion chambers. In any case, the object was to provide good torque with regular fuel and much cooler timing than Buick had ended up using for the bigger Nailhead. It was supposed to be an economy engine, although that didn’t work out because the production costs ended up being much higher than anticipated, even discounting the warranty nightmares. Even the 300 wasn’t intended as a hot rod engine; it was a step-up engine for the A-body and a cheaper base engine for the B-body.
Ford’s foundry work in the days of Henry I were a mixed bag — the flathead V-8 had some strengths and a lot of weaknesses, some not fixed until the fifties. Thinwall casting as used on the Falcon six and Fairlane V-8 was a largely new development, which emerged in the fifties as an offshoot of some work they had done on crankshaft casting. (The basic idea is to add thermosetting resin to the sand cores, so they’re more rigid, and then casting and curing the cores in a preheated box without removing them for heat-treating, so there are fewer opportunities for distortion.) Many other manufacturers subsequently adopted similar techniques for iron engines, but to varying degrees of effect, and they didn’t necessarily save nearly as much weight; perhaps the most notorious example was the late BMC C-series six used in the 3-litre and MGC.
I strongly suspect the reason Ford went as far as they did with those engines was MacNamara. MacNamara insisted on very stringent weight limits for the Falcon — the 1960 Falcon was roughly the size of a Mk3 Mondeo, with a cast iron six, but it had a curb weight of around 2,400 lb — and I think the 144 engine ended up as light as it did (345 lb) because they weren’t going to be able to hit those targets otherwise, forcing the manufacturing people to push the thinwall idea further than they might otherwise. (It was arguably too far; as the Australians found out, the initial Falcon was kind of flimsy for anything but gentle suburban commuting, and later versions of the six were stouter, especially after the switch to seven main bearings.) The 221/260/289/302 was an immediate beneficiary of those efforts.
(I think the lightness of the Buick iron V-6 and V-8 was more a result of starting with a design intended for aluminum, which tends to have to be thicker for comparable strength.)
The 330 is another example of what I mean by not all manufacturers using thinwall casting techniques to the same extent. Olds used thinwall casting for three of the block’s six cores (water jackets and crankcase core), not the whole block, and I don’t think for the heads; they made some design changes like reducing the width of the heads (and adopting more Buick-like combustion chambers) to save some weight, but the use of hot box resin cores was pretty conservative. Hence, the 330 weighed about 40 lb more than a Chevrolet 350 and about 100 lb more than the Ford 289/302. The 425 was not a thinwall engine, despite its similarity to the 330. This was a foundry issue rather than a design one; the design essentially had provision for hot box coring, but didn’t use it, so the 425 was only a little lighter than the 394. (The 455 was, or became, a thinwall engine, but the initial 425 was not.)
I understand that the Nailhead had aggressive valve timing in compensation for the small valves.
To some extent, particularly as displacement increased. For the original 1953 322, intake duration was 282 degrees, with 0.378-inch intake lift and 67 degrees of overlap, which was warmer than the fifties norm. For comparison, the 1955 Packard V-8 had an intake duration of 250 degrees, with 0.375 inches of lift and 32 degrees of overlap; the Packard engine had substantially bigger valves, so it didn’t need as much lift or duration.
However, by the time Buick expanded the Nailhead to 425 cubic inches, intake duration was up to 290 degrees, with 0.439-inch intake lift and 77 degrees of overlap. For comparison, the cam in a 1964 Pontiac 421 H.O. provided 288 degrees’ intake duration, 0.409-inch intake lift, and 63 degrees of overlap, and the non-H.O. 421 and 389 were significantly cooler than that.
Buick actually didn’t back off that much on the timing with the initial 400 and 430 despite their larger valves. Their initial cam profile was 298 degrees of intake duration, 0.421-inch lift, and 61 degrees of overlap.
A point I discovered after making this comment in January is that there’s some variation in nomenclature when it comes to casting methods: Apparently in British (and probably Canadian and Australian) usage, semi-permanent mold casting IS often called die casting, with what American usage calls die casting referred to as “pressure die casting” or “high-pressure die casting.” This had been throwing me; I didn’t realize the terminological confusion until I saw a comment mentioning this point in the discussion section of a technical paper. (That the commenter took the time to spell it out suggests that I’m not the only one who was confused.)
There is still a significant distinction between semi-permanent molds/low-pressure die casting and high-pressure die casting; aside from the much greater pressures involved, pressure die casting imposes certain limits on the shape and design of the cast object (since there has to be a way to remove the die from the casting!).
This is true, but even if it were otherwise, I don’t think the Y-body Tempest had a lot of potential. In this, I mean that the car as it existed was a dead end, short of essentially starting over with an all-new car of similar mechanical configuration: new engine, new suspension, new transaxles, a new body, and probably a largely new marketing direction. There are a number of ways that could theoretically have gone, of varying degrees of plausibility, but when you really come down to it, few if any individual aspects of the 1961–1963 car as it existed were really worth carrying over.
Well, front-wheel drive was not discontinued — the Toronado and Eldorado continued with the UPP FWD layout through 1985, joined for the final stretch by the Riviera. It just wasn’t applied on a wider basis, unless you count the GMC Motorhome.
The rationale for dropping the switch-pitch converter was actually that it created too much noise, which, given that its users were Cadillac, Buick, and Oldsmobile makes a certain amount of sense. It also created an awkward compromise at step-off because the stator was at high angle at idle to reduce creep and then switched to low angle unless you really put your foot in it. When it was dropped for 1968, Olds, Buick, and Cadillac had adopted torquier engines that didn’t need the extra “half-step” of the switch-pitch converter even with taller axle ratios. There’s a discussion of this in the July 1968 Motor Trend, where they actually compared 1967 and 1968 Olds F-85 and Delta 88 cars back to back; with an extra 30 or 40 lb-ft (gross) torque, the ’68s had better performance at all speeds with less commotion.
After late seventies downsizing, it’s possible the switch-pitch converter would have been helpful, but by then, fuel economy concerns brought the return of lockup converters, and a new philosophy of locking up the converter except at very low speeds and keeping it locked up as much as possible. Remembering the double-clunk of eighties three-speed automatics (shift into or out of third, then lock or unlock the converter), I don’t think they would have been greatly improved by adding an additional “stage” with the torque converter stator trying to decide what to do — certainly not subjectively!
So, in that sense, I think it was a feature whose useful had, if not exactly ended, reached a point where the end of the road was in sight.
No, no, Aaron, you are right:
I have left out the 1980 Citation in 1979, the Mopar K-Cars of 1981, and the later Ford Tempo and Taurus.
Please forgive my oversight. I intended to show that Detroit had an attention span issue when bringing a new technology to market, and was also too impatient in promoting those new cars. I think I have a point on these issues, but whether I am right about that or not, I am certainly wrong on front wheel drive being a valid example of those premises.
Oh, I don’t disagree, and it’s entirely fair to criticize the way GM originally approached FWD. As an exercise, the Unitized Power Package for FWD was not dissimilar to the rope-drive Tempest: It was full of clever ideas, applied in a context where they didn’t make a whole lot of sense, and then not really pursued further (although the Toronado and FWD continued with it, which the Tempest did not).
Oldsmobile was initially looking at FWD for a compact car (perhaps a second-generation F-85), but for various reasons, ended up introducing it in the Toronado, where most of the advantages of FWD were basically meaningless. (The Toronado was many things, but “space-efficient” was not on the list, and for a personal luxury car to have a flat floor was more a parlor trick than a useful innovation.) Even then, it wouldn’t have been unreasonable to treat the Toronado as a proof of concept and a way to build acceptance before applying the UPP FWD package to other products where it made more sense, such as the Oldsmobile Vista Cruiser wagon, where having a flat floor, no live axle to compete with cargo and passenger space, and above-average wet traction with V-8 power would have been an intriguing proposition. However, they didn’t do that, and the mainstream FWD cars GM later introduced, beginning with the X-body Citation and its siblings, borrowed nothing from the work done on the Toronado and Eldorado. So, the UPP cars, while well-engineered and well-executed, ended up being a costly and arguably pointless vanity project; the Toronado and Eldorado could just as well have been RWD. (Toronado buyers were generally aware of the car’s FWD and considered it a good feature, but I don’t think most Eldorado buyers cared a whit.)
The big distinction between the Toronado and rope-drive Tempest in this respect is that FWD is better suited to compact family cars (which the Toronado was not) while a front-engine/rear-transaxle layout is better suited to sports cars or high-end GTs (which the Tempest was not). In both cases, though, you had a comparable case of perfectly viable technology being misapplied at a basic product-concept level, and then becoming a dead end. So, that the Tempest would remind you of the Toronado in this way is entirely reasonable!
The possibility this suggests is the idea of applying the rear transaxle to a more expensive car with a more upscale sporty bent than the Y-body compacts. For instance, I could envision something like a 1969 Pontiac Grand Prix with a rear transaxle derived from Turbo Hydra-Matic. I don’t know how such a thing would have gone over commercially, since it would have been more expensive than the actual ’69 Grand Prix, and even with independent rear suspension, my strong suspicion would be that Pontiac would have found a way to make it ride and handle like any other big GM car, rendering it essentially another technological dead end, just in a different segment.
(Ford’s adoption of FWD is a more complicated story, some of which is discussed in the article on the Fiesta. Ford’s first foray into FWD was the Cardinal project, which became the German Taunus 12M/15M (P4 and P6). This was subsequently dropped in favor of the RWD Escort and a German version of the RWD Cortina, but Ford — very reluctantly — adopted a more modern transverse FWD layout for the Mk1 Fiesta in 1976, and then for the FWD Escort in 1981. The latter then spawned the larger Tempo/Topaz in the U.S. and the Ford Orion sedan in Europe. The Cardinal/Taunus P4/P6 was also sort of a dead end, especially considering that it was supposed to be offered in the U.S. and never was.)
Wow – another thorough article. Even though I was quite into cars in the 1961-3 time-period, I had never heard the term “Polaris” or seen photos. Didn’t realize that the 326 started out as a 337 either.
My recollection is that all 61/62 Tempests had the three chrome fingers in the cove behind the front wheel cutouts, and that all Le Mans cars had the rear fender peak moldings. I am surprised that the Pontiac was any longer than the Olds or Buick.
Thanks again for such wonderful writing and insights.