With all the furor surrounding Ford and Chevrolet’s new 300+ horsepower V6 Mustang and Camaro, you would think hot six-cylinder engines were a new idea, at least in America. Not so — in 1965, about a decade after the demise of the Hudson Hornet and its “Twin H-Power” straight six, Pontiac introduced a sophisticated new overhead cam six-cylinder engine that promised V8 power and six-cylinder economy. This week, we look at the short life of the 1966–1969 Pontiac OHC six, Pontiac Firebird Sprint, and Tempest Le Mans Sprint.

(Photo © 2006 Robert Nichols; used with permission)

JOHN DELOREAN AT PONTIAC

John Zachary DeLorean was born in Detroit in 1925. Like many automotive executives of his era, he was a second-generation automobile man; his father, an immigrant from Alsace-Lorraine, had worked for a time as a millwright for Ford. As a teenager, DeLorean earned a scholarship to Lawrence Institute of Technology (now Lawrence Technological University) and, after a brief stint as an insurance salesman, took a job with the Chrysler Corporation. In 1952, he joined the Packard Motor Car Company, working with Forest McFarland, Packard’s chief R&D engineer, on projects like the second-generation Ultramatic transmission.

Packard was quite small by the standards of domestic automakers, with a deeply ingrained culture of unhurried Old World craftsmanship. Largely unencumbered by bureaucracy and nurtured by the ever-patient McFarland, DeLorean thrived, enjoying a level of autonomy rare in a conservative industry. When McFarland departed to join Buick in 1956, DeLorean was promoted to replace him as head of R&D.

If the Studebaker-Packard Corporation had been healthier, DeLorean might have enjoyed a fine career there. Unfortunately, by 1956, the company was staggering toward collapse. That summer, the Studebaker-Packard board decided to eliminate Packard’s own design and manufacturing facilities, consolidating development and production at the Studebaker plant in South Bend, Indiana. DeLorean started looking for other job opportunities.

He was soon contacted by Oliver K. Kelley, then the head of GM’s corporate Transmission Development Group (and one of the principal architects of the original Hydra-Matic and Dynaflow transmissions). Kelley made a concerted effort to recruit DeLorean and arranged a series of interviews for him, including a meeting with new Pontiac general manager Semon E. “Bunkie” Knudsen.

Although DeLorean was wary of GM’s top-heavy corporate culture and put off by Pontiac’s stodgy reputation, Knudsen convinced him that they could reinvent Pontiac and offered him a lucrative salary (around $14,000 a year, a handsome sum in the mid-fifties) to become the head of Pontiac’s new advanced engineering section.

DeLorean arrived at Pontiac on September 1, reporting to new chief engineer E.M. (Pete) Estes, whom Knudsen had recently recruited from Oldsmobile. DeLorean’s role was to develop new engineering concepts that might eventually find their way into production Pontiacs. As at Packard, he was given a free hand to explore novel and sometimes radical ideas, ranging from a rear transaxle with an unusual flexible driveshaft (subsequently used for the 1961–1963 Pontiac Tempest) to an experimental six with an unusual combination of air- and water-cooling.

Unlike most American compacts of its era, the 1961–1963 Pontiac Tempest did not use or offer a six-cylinder engine. Most 1961–1963 Tempests were powered by a 196 cu. in. (3,186 cc) slant-four engine — essentially Pontiac’s 389 cu. in. (6,372 cc) V-8 shorn of one cylinder bank. Buick’s 215 cu. in. (3,528 cc) V8 was optional in 1961-1962, but rarely ordered; fewer than 5% of buyers selected it. (Photo © 2009 Norm Stephens; used with permission)

By 1959, DeLorean had embarked on a new project: an advanced six-cylinder engine with a single belt-driven overhead camshaft.

ORIGINS OF THE PONTIAC OHC SIX

In the early sixties, six-cylinder engines were enjoying a modest resurgence in the American market. A decade earlier, buyers had shown a marked preference for the new breed of OHV V-8s, leading some mid-priced automakers to abandon sixes entirely. Pontiac had dropped its venerable flathead six at the end of the 1954 model year and didn’t offer another six-cylinder engine until 1964. The sharp recession that began in 1957 sent the pendulum swinging the other way, leading to a new generation of six-cylinder compacts. Pontiac had bucked that trend with the four-cylinder Tempest, but it was clear that the division would need a new six eventually. That also presented an attractive opportunity to explore new ideas.

Both DeLorean and motor engineer Malcolm McKellar were intrigued with OHC engines both for their practical advantages (see the sidebar above) and for their rather racy connotations. Although overhead camshafts were very rare for American production cars, they were almost de rigueur for European racing engines, and DOHC Offenhauser racing engines had been extremely successful at the Indianapolis 500 for many years.

Jaguar was another firm adherent of overhead cams; its XK six (pictured here in a 1963 Jaguar E-Type fixed-head coupé) had dual overhead cams while Jaguar’s later V12 was SOHC. This engine had an enviable pedigree: In competition trim, it won the 24 Hours of Le Mans five times.

The direct inspiration for Pontiac’s OHC engines was the contemporary Mercedes big six, a 183 cu. in. (2,996 cc) engine found in the Mercedes 300 sedans and coupes and, in somewhat more highly tuned form, the 300SL sports cars. With its iron block and single overhead camshaft, the Mercedes-Benz engine was not as exotic as the twin-cam engines from Jaguar and Alfa Romeo, but it had an impressive competition pedigree and offered a fair compromise between power, fuel economy, and complexity. It became the conceptual starting point for Pontiac’s design work.

THE TIMING BELT

The major objections to overhead cams for mass-production engines had always been cost and complexity. Most gear-driven overhead cams were prohibitively expensive for non-racing use and unacceptably noisy to boot. Chain drive, used by most production OHC engines of the fifties, was somewhat simpler, but still entailed a relatively high level of mechanical noise, not to mention the challenges of maintaining proper chain tension and lubrication.

An intriguing alternative was using a cogged rubber belt, like the Gilmer belts used to drive mechanical superchargers. A belt is quieter than a chain or gear drive, weighs less and thus consumes little power, and requires no lubrication. Better still, it’s considerably cheaper than either gears or chains.

The Pontiac OHC six’s timing belt did not normally require adjustment, but the tension could be adjusted if necessary by moving the front cover. Unlike some later OHC engines, the Pontiac cammer is not an interference engine. If the timing belt breaks, it will immediately stop the engine, but it will not normally cause valve or piston damage, a serious risk with some OHC layouts. (Photo © 2006 Robert Nichols; used with permission)

Belt-driven camshafts were not a new idea even then. In the mid-fifties, racing engine builders had begun experimenting with belt-driven DOHC heads, including a 1955 Cadillac V-8 conversion. Although those early efforts were not very successful, they attracted the attention of the United States Rubber Company (later known as Uniroyal), which sensed a potentially lucrative new market; Uniroyal started developing automotive timing belts around 1956. Pontiac began its own experiments in 1959, initially using stationary engines.

Around the time the OHC six project began in earnest, the German automaker Glas introduced the 1004-S coupe, the first production car with a belt-driven OHC engine. The Glas engine, initially displacing 993 cc (61 cu. in.) and eventually expanded to 1,682 cc (104 cu. in.), proved durable and reasonably dependable, although Glas engineers hedged their bets by recommending timing belt changes every 25,000 miles (40,000 km).

The Glas engine was encouraging, but developing a timing belt adequate for a torquey big-bore six still presented a problem, particularly since McKellar was determined to find a belt that would last the useful life of the engine. Simple rubber belts weren’t strong enough or durable enough; reinforcing the belt with steel cords provided adequate strength, but the steel would rust and eventually weaken. Using stainless steel cords eliminated the corrosion problems, but was much too expensive and showed worrisome signs of fatigue at high mileage.

Pontiac’s eventual solution, developed in collaboration with Uniroyal engineer Richard Case, was a 1-inch (25-mm) wide, fiberglass-reinforced, neoprene-impregnated nylon fabric belt, which proved to be strong and durable, demonstrating minimal wear in high-mileage testing. Unlike some later automotive timing belts, it was not overly sensitive to dirt and oil, although Pontiac ultimately decided to keep it covered to protect it from snow and road spray.

Another of the bugbears of early overhead cam engines was the need for periodic valve lash adjustment. That, too, was unacceptable to Pontiac, whose divisional policy mandated hydraulic valve lifters (which needed no adjustment in normal use and prevented over-revving) for all engines carrying a full factory warranty. Hydraulic lifters had never been seen as practical for OHC engines, but Pontiac developed a clever solution, a variation of a concept GM had developed and patented in the mid-fifties for pushrod engines. Although the OHC six’s camshaft was mounted almost directly above the valves, it actuated them through finger-type cam followers — essentially small rocker arms — each of which was pivoted on a small hydraulic sphere that functioned like a hydraulic lifter. The pressure exerted by the sphere served to maintain a constant zero valve lash, reducing mechanical noise and eliminating the need for routine valve adjustments without adding to reciprocating mass or inertia.

The Pontiac OHC six had an iron block and head, but the cam cover (where the camshaft is actually mounted) and the timing belt cover are both die-cast aluminum, helping to keep total engine weight to 489 lb (222 kg). Note the location of the distributor; it’s driven by a shaft running along the side of the block along with the oil pump and fuel pump. (Photo © 2006 Robert Nichols; used with permission)

The rest of the engine was a study in compromise. The cast iron block was loosely based on that of Chevrolet’s 1962-vintage OHV six and shared the Chevrolet engine’s connecting rods and seven-main-bearing crankshaft. However, Pontiac extended the skirt below the crankshaft center line for greater rigidity, much as Ford had done with its old Y-block V-8. (The deep skirt also allowed the use of cross-bolted main bearings, although these were specified only for the more powerful iterations.) Bolted to the right side of the block was an aluminum carrier for the accessory drive, including the gear-driven distributor and fuel and oil pumps. The accessory shaft sprocket was driven by the timing belt and did double duty as a belt tension adjuster.

The cast iron cylinder head used wedge combustion chambers with side-by-side valves like those of Pontiac’s V-8s, but the camshaft was actually mounted in an aluminum cam carrier rather than in the head itself and had very wide lobes to minimize wear. The valves, shared with Pontiac’s V-8s, were quite large: Intake diameter was 1.92 inches (48.8 mm) while exhaust diameter was 1.60 inches (40.6 mm), the biggest the ports would accommodate.

Despite its novel features, the Pontiac engine was more mildly tuned than were most of its European contemporaries. The basic version had a modest specific output of 0.72 hp/cu. in. (44 hp/liter), compared to 1.08 hp/cu. in. (65 hp/liter) for the big Mercedes six. On the other hand, the Pontiac engine was designed to be dependable and free of temperament, which could not necessarily be said for its more exotic British, German, and Italian rivals. It was not unlike Hollywood remakes of popular European films: retaining the basic plot of the original, but recast with familiar faces and a bigger effects budget.

OHC EIGHTS

Prototypes of Pontiac’s OHC six were running on test stands by the spring of 1962, but development and testing of the production engine was protracted and it was not production ready for another two years. However, that didn’t stop Mac McKellar from applying some of its concepts on a considerably larger scale.

For the past few years, Pontiac had been a major player in NASCAR competition, working surreptitiously with private teams to get around GM’s official no-racing policy. By 1962, NASCAR had become an arms race between the major automakers, each of whom fielded an array of increasingly specialized engines and equipment. Pontiac’s most recent salvo was the Super Duty 421, a ferocious 6,902 cc engine laughingly underrated at 405 gross horsepower (302 kW) with two four-barrel carburetors. It was essentially a hand-built engine, offered to the public only in tiny numbers for homologation purposes.

Despite its power, the Super Duty was hard pressed by the latest Chrysler and Chevrolet engines, particularly the new Chevrolet Mark II “Mystery Motor” that appeared in early 1963. To remain competitive in NASCAR, Pontiac would need something more.

McKellar’s solution was an overhead cam conversion of Pontiac’s 389 cu. in. (6,372 cc) V-8, drawing on concepts developed for the OHC six. Where the six sacrificed outright sophistication in favor of lower production costs, the 389 had no such compromises; it had 32 valves, belt-driven dual overhead camshafts (using a more robust version of the six’s belt drive), a cross-ram intake manifold, and sequential fuel injection. Pontiac never released power figures for the DOHC engine, but it probably made well over 500 gross horsepower (373 kW).

Unfortunately, the twin-cam 389 never made it to the racetrack. In early 1963, GM chairman Frederic Donner issued a tersely worded memo reiterating the corporate ban on racing, adding that under-the-table participation would no longer be tolerated. Pontiac’s DOHC engine went back on the shelf, although the division continued to work on OHC V-8s on an experimental basis. Toward the end of 1963, McKellar developed a simpler SOHC 421 with 16 valves and one belt-driven cam per bank, capable of some 620 hp (462 kW) with Tri-Power carburetion. This was followed in 1965 by a 24-valve SOHC version of the newer 428 cu. in. (7,008 cc) engine.

McKellar showed off the experimental engines to Hot Rod editor Eric Dahlquist in 1968, but none of the OHC V-8s made it to even limited production. Forbidden to race, Pontiac had little need for them, and the growing safety lobby had left GM management wary of fielding very powerful engines. A 500 horsepower (373 kW) OHC V-8 would have been a provocative gesture as far as Washington was concerned, and the GM brass was in no mood for provocative gestures.

THE BANSHEE

While it originated in DeLorean’s Advanced group, the OHC six, unlike the V-8s, was always intended as a production engine. Its prospects for production improved significantly in November 1961 when DeLorean was promoted to chief engineer, succeeding Pete Estes, who replaced Bunkie Knudsen as general manager. Although the six was destined to become the base engine in Pontiac’s A-body intermediate line, its first application was DeLorean’s most ambitious project to date: the two-seat Pontiac Banshee.

The Banshee project, known internally by its styling code, XP-833, began in August 1963. Designed by Roger Hughet and Ned Nickles of the Advanced Design Studio, it was a compact fastback coupe, looking something like a miniature Corvette Sting Ray. To minimize tooling costs, XP-833 used a fiberglass body with a steel floorpan, although it borrowed most of its running gear from the new A-body Tempest. The OHC six was to be the base engine, although the second prototype was powered by a Pontiac V-8. DeLorean conceived it as an inexpensive sports car, a competitor for the new Ford Mustang.

Not counting the early non-running mockups, there were two Pontiac Banshee prototypes: a coupe and a roadster. The coupe was powered by a base one-barrel OHC six, while the roadster was originally powered by a 326 cu. in. (5,340 cc) Pontiac V-8, which probably would have been optional if the Banshee had made it to production. (Photo: “pontiac_banshee_2” © 2009 EvThoMcC; used with permission)

GM management was unenthusiastic about the Banshee, preferring Pontiac to instead join Chevrolet’s new F-body sporty-car program. Estes and DeLorean still believed the XP-833 was a viable concept, but they realized that the corporation would kill it if they continued developing it through normal channels, so DeLorean assigned Advanced Engineering chief Bill Collins to continue the project in secrecy.

In the summer of 1965, DeLorean was promoted to general manager of Pontiac. Seeing his opportunity, DeLorean had Collins show off the two fully finished XP-833 prototypes to senior management, along with a beautifully illustrated presentation that detailed the Banshee’s expected market position, tooling costs (well under $20 million), and projected sales (about 32,000 a year). With a starting price of $2,500, the Banshee would compete directly with the Mustang and would help to bolster Pontiac’s sporty image.

Unfortunately, Donner and GM president Jim Roche were not interested. They thought the XP-833’s lack of rear seats would limit its sales potential and worried that the car would cannibalize sales of the more expensive and more profitable Chevrolet Corvette. DeLorean continued fighting for the Banshee until the spring of 1966, but Ed Cole, GM’s executive vice president, finally ordered him to forget it and develop a Pontiac version of the F-body, which became the 1967 Pontiac Firebird.

To DeLorean and Collins’ great annoyance, not long after rejecting the XP-833 project, Roche and Donner approved production of the conceptually similar (and similar-looking) Opel GT, based on the European Opel Kadett sedan. The GT was roughly the same size as the Banshee, but it used a steel body and four-cylinder engines. To add insult to injury, it was sold in the U.S. through Buick dealers, not by Pontiac.

TEMPEST SPRINT

The failure of the Banshee did not mean the end of the OHC six, which finally went into production in the summer of 1965. That fall, it replaced a Chevrolet-derived 215 cu. in. (3,529 cc) pushrod six as the standard engine of the 1966 Pontiac Tempest/Le Mans.

In its initial form, the Pontiac OHC six displaced 230 cubic inches (3,769 cc), the same as the pushrod six used by the Chevrolet Chevelle/Malibu. The base engine, with a mild cam and a single-barrel Rochester carburetor, made slightly less torque than the Chevrolet engine — 216 lb-ft (293 N-m) to the Chevy’s 220 lb-ft (298 N-m) — but substantially more power: 165 gross hp (123 kW) to only 140 hp (104 kW) for the OHV Chevy. The OHC engine was not enough to make the Tempest a fast car, but it was a bit quicker than most contemporary American sixes.

The automotive press had known the OHC six was in the works for more than a year, but its arrival still made a great splash. Nearly every automotive magazine ran in-depth articles on the new six, speculating what it heralded for future Detroit engines. The buff books were particularly excited about the optional four-barrel version of the new engine, which Pontiac advertised as the answer to exotic European engines.

The Sprint version of the OHC six had 10.5:1 compression, a big Rochester Quadra-Jet carburetor, and unique intake and exhaust manifolds with separate runners for each port. The 1967 version, pictured here, was rated at 215 horsepower (160 kW), giving it a nominal specific output of 0.93 hp/cu. in. (57 hp/liter), although that was based on the old SAE gross rating system; we would guess that its net output was somewhere between 150 and 160 hp (112 and 119 kW). (Photo © 2006 Robert Nichols; used with permission)

The four-barrel OHC engine had the same displacement as its more mundane sibling, but had new intake and exhaust manifolds, a hotter camshaft, and a higher compression ratio. In 1966, it was rated at 207 gross horsepower (154 kW) and 228 lb-ft (309 N-m) of torque, which was, as Pontiac advertising inevitably pointed out, more than many small-block V-8s of the time. Chevrolet’s basic 283 cu. in. (4,638 cc) engine, for instance, was rated at only 195 hp (145 kW).

The four-barrel engine was marketed as part of a Sprint package that included stiffer shocks, side stripes, and other cosmetic details. Priced at $126.72, the Sprint package was available on any Tempest or Le Mans except station wagons. Pontiac marketed it as a European-style sports sedan, although most reviewers saw it as a sort of six-cylinder GTO. Naturally, the Sprint wasn’t as fast as the GTO, but its straight-line performance was more than adequate — 0-60 mph (0-97 km/h) took less than 9 seconds and top speeds of 115 to 118 mph (185 to 190 km/h) were possible. With less weight on the nose than a GTO, the Sprint also handled and stopped better. The hotter six was not particularly strong below 3,000 rpm, but it was tractable enough, and many reviewers were entranced with its Jaguar-like growl.

The Sprint package was available on any A-body Pontiac except wagons, but most went into coupes and two-door hardtops. It’s seen here on a 1967 Pontiac Tempest Custom convertible (with wheel covers from a ’62 Pontiac). (Photo: “1967 Pontiac Tempest Sprint OHC” © 2006 Mark Sevigny; used with permission)

Indeed, the Jaguar comparisons were tempting enough that Pontiac ad man Jim Wangers persuaded Doc Watson of Hurst Performance Products to install a Sprint engine and four-speed in a well-worn 3.8 E-Type. Hurst turned it over to Car and Driver, which found it somewhat slower than a healthy Series I E-Type, so Hurst added a trio of Weber carburetors and a few other shade-tree hot-rodding tricks that brought the engine to a claimed 315 horsepower (235 kW). Despite the magazine’s enthusiasm, the Pontiac-engined Jag didn’t inspire a raft of imitators, but it did attract a lot of attention, which was the point of the exercise. (The converted car was later purchased by Ford engineer Don Coleman, who substituted a 300 cu. in. (4,918 cc) Ford six for the Pontiac cammer.)

The publicity and favorable reviews were not enough to make the Sprint a runaway success. Total production for 1966 was fewer than 20,000 units, compared to nearly 97,000 ’66 GTOs. While the hot OHC engine was novel, it was not powerful enough to entice horsepower-crazed teenagers, and the few customers interested in fuel economy in 1966 usually settled for the base engine. (Pontiac claimed the Sprint engine was capable of 20 mpg (11.8 L/100 km), but based on Popular Mechanics owner surveys, even the base engine was hard-pressed to return more than 17.5 mpg (13.4 L/100 km) in normal driving.) Even Car and Driver, for all its enthusiasm for the concept, reluctantly concluded that the V-8 was the more sensible choice for the intermediate A-body. Despite the OHC engine, the Tempest/Le Mans Sprint was no sports sedan and many observers wondered if the hot six would do better in a smaller, lighter, sportier car.

The Sprint’s greatest rival was not any competitor, but Pontiac’s own 326 cu. in. (5,340 cc) V-8. The 326 was thirstier and less sophisticated, but it offered 250 horsepower (187 kW) for less money than the four-barrel OHC six.

FIREBIRD SPRINT

By the time the Tempest/Le Mans Sprint entered its second model year, Pontiac was busily readying the Firebird for its mid-year introduction. When the Firebird went on sale in late February 1967, the 165 hp (123 kW) OHC six was standard and the Sprint package was one of four engine options.

As with the Tempest/Le Mans Sprint, the Pontiac Firebird Sprint package included side stripes, special badges, and stiffer shocks, along with the four-barrel OHC engine. It was very rare; we were unable to find exact figures, but we estimate that fewer than 5,000 ’67 Firebirds were Sprints. (Photo © 2006 Robert Nichols; used with permission)

On paper, the Firebird looked like a much better home for the Sprint engine than did the A-body Tempest, but the real-world results were less edifying. Although the Sprint engine was now rated at 215 horsepower (160 kW) and 240 lb-ft (325 N-m) of torque, most reviewers found the Firebird Sprint noticeably slower than the 1966 Tempest/Le Mans Sprint, particularly with the California emissions package. Part of the problem was the fact that the Firebird was not that much lighter than the Le Mans despite smaller external dimensions; in fact, Car Life‘s well-equipped 1967 Firebird Sprint was actually 40 lb (18 kg) heavier than their 1966 Le Mans Sprint hardtop coupe. The Firebird Sprint handled marginally better than its V-8 counterparts did, but it suffered all the suspension infirmities of all early F-bodies, including excessive wheel hop, a choppy ride, and a tendency to lose composure on uneven surfaces.

As with the Le Mans, the Firebird Sprint’s greatest problem was price. Although the four-barrel engine package was not particularly expensive, at $105.60, the 285 hp (213 kW) 326-HO actually cost about $10 less and mated better with the automatic transmission that most buyers preferred. Fewer than 25% of Firebird buyers opted for either OHC six.

Pontiac planned to drum up some interest with a special performance edition known as PFST (Pontiac Firebird Sprint Turismo), a Camaro Z/28-style homologation special for SCCA competition. Developed by engineer Herb Adams, the PFST used a modified version of the Sprint engine fitted with three Weber 40 DCN carburetors that protruded through the hood into a tall reversed scoop. The suspension was extremely stiff with stout anti-roll bars front and rear, giving excellent handling at the expense of a rather brutal ride. Pontiac let magazine testers drive the PFST prototype, but the new model didn’t make it to production. The triple Webers ran afoul of GM’s new ban on multiple carburetion, and even after substituting a bigger Rochester Quadrajet, the modified engine was too loud to pass drive-by noise regulations.

Racing driver John Fitch, who had previously had a modest business selling modified Corvairs, developed his own tuned Firebird, also using the OHC engine. Unfortunately, the package was too expensive for most buyers. Fitch built only a handful of modified Firebirds, only one of which had the six-cylinder engine.

Although most contemporary magazine reviewers tested Sprints with the four-speed manual, the vast majority of buyers opted for the optional automatic; either transmission cost $184.31 more than the standard three-speed stick. The two-speed automatic (Buick’s Super Turbine 300, not the Chevrolet Powerglide) blunted the Sprint’s performance considerably. With automatic, the 0-60 mph (0-97 km/h) dash took around 12 seconds. (Photo © 2006 Robert Nichols; used with permission)

THE DECLINE AND FALL

Going from advanced engineering chief to chief engineer and then general manager was a mixed blessing for John DeLorean. His increased authority also chipped away at his former autonomy — there was ever-increasing pressure to meet cost targets and adhere to conservative corporate policy. DeLorean’s clashes with senior management were seemingly endless, which made him many powerful enemies within the corporate hierarchy.

The OHC six eventually became another point of contention. DeLorean’s immediate superiors, GM group vice president Roger Kyes and executive vice president Ed Cole (who became GM president in the fall of 1967), were always unhappy about its high costs. Although Mac McKellar had done everything possible to minimize those costs, including sharing some parts with the contemporary Chevrolet six, the OHC engine was still more expensive to build than was its Chevrolet cousin. The OHC six also had higher warranty costs; while the timing belt itself was reliable, there were problems with premature camshaft wear and sticking valve lash adjusters. None of these issues was insurmountable, but they did nothing to win the confidence of an already skeptical corporate management.

For 1968, Pontiac stroked the OHC six from 3.25 to 3.53 inches (82.6 to 89.7 mm), bringing total displacement to the same 250 cu. in. (4,095 cc) as Chevrolet’s bigger pushrod six, introduced back in 1966. Increasing the OHC engine’s displacement was primarily intended to provide more torque for the heavier 1968 A-bodies and help the engine better cope with the new 1968 federal emissions standards, but Pontiac also added a new crankshaft with 12 counterweights rather than four, similar to the crank in the Chevrolet 250.

Pontiac claimed that the base OHC six now had 175 gross horsepower (131 kW), 10 hp (7.5 kW) more than before and 20 hp (15 kW) more than the pushrod Chevrolet six. Both the base and Sprint engines also had more torque: 240 lb-ft (325 N-m) and 255 lb-ft (346 N-m) respectively. However, the longer stroke made the Sprint engine noticeably less eager to rev, so its performance was not notably improved. Pontiac made a last effort to rectify that in 1969 by introducing two new camshafts for the Sprint engine. Cars with automatic again had 215 hp (160 kW), but slightly more torque, now 260 lb-ft (353 N-m); manually shifted cars, with more valve overlap, had 230 hp (172 kW) and 255 lb-ft (346 N-m).

Unfortunately, the interest of both buyers and the enthusiast press had by now mostly faded, so sales of the six continued to decline. That in turn made it harder than ever for Kyes and Cole to accept the OHC engine’s higher costs. A further problem was that the OHC engine was too tall to fit in the engine bay of the forthcoming second-generation Firebird without bulging the hood. As with the Banshee, DeLorean continued to fight for the OHC engine, but it was to no avail. DeLorean left Pontiac for Chevrolet in early 1969 and the OHC expired soon after that; starting in 1970, Pontiac would buy the cheaper 250 cu. in. (4,095 cc) Chevrolet six instead.

The 1969 model year was the end of the line for both the one-barrel OHC six and the Sprint option. The standard engine was now rated at 175 gross horsepower (131 kW); the Sprint had up to 230 hp (172 kW) with manual transmission. Sales were very low; we don’t have a precise figure, but it was probably fewer than 5,000 units. (Photo © 2006 Robert Nichols; used with permission)

DeLorean’s successor at Pontiac, F. James McDonald, was a production man, not an engineer, and shared neither DeLorean’s interest in technological novelty nor his penchant for battling management. Once the OHC six was dead, the OHC V-8s were also canceled, as were a number of experimental derivatives of the six. Pontiac’s engineering focus shifted to emissions control; high-revving, high-performance engines seemed increasingly anachronistic.

The cancellation of the OHC six was unfortunate because less than five years later, the OPEC oil embargo sent Pontiac engineers scrambling to find smaller, more fuel-efficient engines. Unlike Buick’s resurrected V-6, whose tooling had been sold to Kaiser Jeep and then to AMC, the tooling for the cammer was probably long gone by then, leading Pontiac to develop the undistinguished 301 cu. in. (4,942 cc) V-8 instead. Had the OHC six survived, it probably would have done very well in the seventies. Even the Sprint might have found its niche, appealing to performance-minded buyers who couldn’t afford the insurance premiums on a GTO.

LEGACY

The next GM car to offer a belt-driven overhead camshaft was the Chevrolet Vega, which debuted in 1971. It spawned a Pontiac version, the Astre, in 1975, although Pontiac didn’t use the Vega’s 140 cu. in. (2,286 cc) OHC engine for long. For 1978, the Vega four was replaced by the 151 cu. in. (2,471 cc) pushrod “Iron Duke” engine, which Pontiac used well into the eighties.

By the late seventies, belt-driven overhead cams were becoming very popular, particularly on inexpensive four-cylinder engines. Sadly, many later timing belts were far less robust than Pontiac’s was, and some OHC engines had an alarming tendency to eat valves if the belt snapped. By the beginning of the 21st century, concerns over belt longevity — and the high cost of changing a timing belt on a modern transverse engine — prompted a move back to timing chains. Timing belts are now becoming rare; even Honda, long a timing belt proponent, has adopted chain drive for its more recent engines.

Hydraulic valve adjusters for OHC engines were slower to spread to other mass-market cars, although they began appearing on some luxury cars in the early seventies. They are now almost universal on OHC engines, mostly to help control exhaust emissions. (Having owned several cars that required valve adjustments every 15,000 miles (24,000 km), the author also considers hydraulic lash adjusters a tremendous convenience.)

It’s unfortunate that the Pontiac OHC six became something of a dead end. The Sprint, in particular, offered a combination of decent power, modest weight, and respectable fuel economy that was not seen again on an American car for years afterward. Along with the turbocharged Oldsmobile Jetfire V-8 of a few years earlier, it was among the most sophisticated American engines of its era. The OHC six had its faults, but none of them was crippling, and most can be rectified today with a competent rebuild and regular oil changes.

The stillborn OHC V-8s are even more tantalizing. Even if they had made to production, it would probably have been on a very limited basis, like the earlier Super Duty engines. However, if DeLorean and McKellar had gotten their way, the performance engines might well have spawned mass-production derivatives, if only for homologation purposes. It’s easy to understand why the prospect of bolt-on OHC heads for the GTO had buff book editors salivating.

Unfortunately, it was not to be. Only one of Pontiac’s OHC V-8 engines made it to the street, a SOHC 421 that Mac McKellar received as a parting gift on his retirement in 1982. Installed in McKellar’s 1963 Grand Prix, it was a fearsome sleeper, a sad — and potent — reminder of opportunities missed.

FIN

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AUTHOR’S NOTE

A little over a year after this article was written, we learned of the death of Malcolm McKellar, who passed away on April 8, 2011. He was 90 years old. McKellar outlived his former boss, John DeLorean, by six years: DeLorean died in 2005 at the age of 80.

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NOTES ON SOURCES

Our sources on the development of the “Cammer” included Jim Black, “Buyer’s Guide: 1966-’67 Pontiac Le Mans Sprint,” Hemmings Muscle Machines June 2009, and “Pontiac’s Fantastic Six,” (n.d., The Pontiac-Oakland Club Overhead Cammers Chapter website, www.overheadcammerschapter. 150m. com, accessed 10 April 2010); Ray T. Bohacz, “Mechanical Marvels: Chain Gang: Exploring Camshaft Drive Mechanisms,” Hemmings Classic Car #12 (September 2005), pp. 66–69; Marc Cranswick, Pontiac Firebird – The Auto-Biography (Car & Motorcycle Marque/Model) (Poundbury, Dorchester: Veloce Publishing, 2003); Christopher M. Drew, assignor to General Motors Corporation, “Rocker Adjusting Mechanism,” U.S. Patent No. 2,934,051, filed 28 May 1956, published 26 April 1960; John Ethridge, “Tempest’s New Cammer!” Motor Trend Vol. 17, No. 9 (September 1965), pp. 40-44; Kit Foster, “1967 Pontiac Firebird Sprint: OHC from John Z’s PMD,” Special Interest Autos #150 (November-December 1995), reprinted in The Hemmings Motor News Book of Pontiacs: driveReports from Hemmings Special Interest Autos, ed. Terry Ehrich (Bennington, VT: Hemmings Motor News, 2001), pp. 118-127; John Gunnell, Standard Catalog of GTO, 1961-2004 (Iola, WI: Krause Publications, 2003); Wick Humble, “1961 Pontiac Tempest: But cars aren’t supposed to have curved driveshafts,” Special Interest Autos #48 (November-December 1978), reprinted in The Hemmings Motor News Book of Pontiacs , pp. 78-86; Roger Huntington, “Much More Muscle for 1966,” Car Life Vol. 12, No. 10 (November 1965), pp. 57–60; Don Keefe, “Department X: The 1964 OHC-6 Banshee Coupe,” High Performance Pontiac November 2001, pp. 38–41, and “Grand Performance: Pontiac’s luxurious muscle car: the 1964 Grand Prix,” Special Interest Autos #195 (June 2003), pp. 24–31; Jeff Koch, “John Z. DeLorean: Thoughts and memories from the immortal creator of the GTO, 30 years later,” High Performance Pontiac February 1994, pp. 22-23; Alex Markovich, “New Cars: What’s Ahead in 1966?” Popular Mechanics Vol. 124, No. 4 (October 1965), pp. 96–100, 219–220H; George Mattar, “1966 Progressive Pontiac: PMD’s advanced overhead-cam-six Tempest for 1966,” Hemmings Classic Car #7 (April 2005), pp. 46–53; “McDonald, F. James,” Generations of GM History, GM Heritage Center, history.gmheritagecenter. com/wiki/index.php/ McDonald,_F._James, accessed 11 September 2015; Mike Mueller, “When Less Was More: Pontiac Overhead-Cam Six-Cylinder,” American Horsepower: 100 Years of Great Car Engines (St. Paul, MN: MBI Publishing Company, 2006), pp. 117-121; Eric Nielssen, “Pontiac’s New SOHC Six,” Car and Driver September 1965, reprinted in Car and Driver on Pontiac 1961–1975, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1986), pp. 36-38, 59; “1966 at GM: Plastic Grille, OHC 6 Among Pontiac Innovations This Year,” Car Life Vol. 12, No. 10 (November 1965), pp. 50–52; Jan P. Norbye, “How Hot Can a Six Get?” Popular Science Vol. 188, No. 6 (June 1966), pp. 70-73, and “Sensational New OHC Six from Pontiac,” Popular Science Vol. 187, No. 2 (August 1965), pp. 37-41; Jan P. Norbye and Jim Dunne, Pontiac 1946-1978: The Classic Postwar Years (Osceola, WI: Motorbooks International Publishers & Wholesalers, 1979); the Old Car Brochures website (oldcarbrochures.org); Pontiac Motor Division of General Motors Corporation, “Four leading car experts report on Pontiac’s Break Away Squad for ’69—” [brochure], September 1968]; Jim Schild, Original Pontiac Firebird and Trans Am 1967-2002: The Restorer’s Guide (St. Paul, MN: Motorbooks, 2007); and J. Patrick Wright, On a Clear Day You Can See General Motors: John Z. DeLorean’s Look Inside the Automotive Giant (Chicago, IL: Avon Books, 1980).

Additional technical details came from Ray T. Bohacz, “Mechanical Marvels: Henry’s Bent Eight: The 1954 Ford 239-cu.in. V-8 engine,” Special Interest Autos #195 (June 2003), pp. 54–56; Doc Frohmader, “Pontiac OHC” (2006, Webrodder.com, www.webrodder. com, accessed 14 April 2010); Donald J. Hoffman, 1966, “Hydraulic Lash Adjuster,” U.S. Patent No. 3,273,548, filed 29 September 1965 and issued 20 September 1966; Michael Lamm, “Fishbowl: 1955 Ford Crown Victoria Skyliner” from Special Interest Autos #37 (November-December 1976), reprinted in The Hemmings Motor News Book of Postwar Fords: driveReports from Special Interest Autos magazine, eds. Terry Ehrich and Richard Lentinello (Bennington, VT: Hemmings Motor News, 2000), pp. 48–55; and Jan P. Norbye, “Comparing the Compacts: Valiant • Falcon • American • Chevy II,” Popular Science Vol. 187, No. 5 (November 1965): 90–94, 184.

Information on Pontiac’s other OHC engines came from Eric Dahlquist, “Big Medicine from Pontiac,” Hot Rod March 1968, pp. 30-35; Don Keefe, “Dept. X: Malcolm ‘Mac’ McKellar’s 1963 Grand Prix is powered by the world’s only surviving OHC 421 Pontiac V8!” High Performance Pontiac October 1990, pp. 30-31; Rocky Rotella, “Pontiac V8 Engines – Photographing Legends,” High Performance Pontiac March 2010, www.highperformancepontiac. com, accessed 10 April 2010; and Bob Wicker, “An Interview with Herb Adams” (January 2010, Pontiacs Online, www.pontiacsonline. com, accessed 10 April 2010).

Additional background information on other American OHC engines came from the Auto Editors of Consumer Guide, Encyclopedia of American Cars: Over 65 Years of Automotive History (Lincolnwood, IL: Publications International, 1996); Ray T. Bohacz, “Mechanical Marvels: Only in a Jeep: The 1962 Willys Overhead Camshaft 6-cylinder Engine,” Special Interest Autos #187 (January-February 2002), pp. 54–56; Jim Bollman, “Crosley Engine Family Tree,” Crosley Automobile Club, n.d., crosleyautoclub. com/EngineTree/ Crosley_Eng_Tree-1.html, accessed 24 May 2020; John R. Bond, “Willys 4wd Wagoneer,” Car Life Vol. 10, No. 3 (April 1963), pp. 54–61; “Evolution of the Wills St. Claire” (2008, Wills Ste. Claire Museum, www.willsautomuseum. org, accessed 11 April 2010); Pat Foster, “The Other Overhead-Cam Six,” Special Interest Autos #150 (November-December 1995), reprinted in The Hemmings Motor News Book of Pontiacs, p. 123; John Gunnell, ed., Standard Catalog of American Cars 1946-1975 Revised 4th Edition (Iola, WI: Krause Publications, 2002); Roger Huntington, “Will Camshafts be Kicked Upstairs? Progress Report on Overhead Cam Development, Yesterday, Today or Tomorrow?” Motor Trend Vol. 16, No. 7 (July 1964), pp. 56-57, 90-92; and Maximiliano Pallocchini, “Tornado: Historia, creación y origenes,” Club Amigos del Torino, 3 August 2012, www.clubamigosdeltorino. com.ar/ index.php/ component/ k2/ item/ 5-tornado-historia-creacion-y-origenes.html, accessed 4 August 2015.

Some information on the Red Baron came from Moldy Marvin, “The Tom Daniel Story” (2004, Ratfink.org, www.ratfink. org, accessed 11 April 2010).

We also consulted the following period road tests: Jim Dunne, “’66 Tempest: A tiger in performance, a dog on gas,” Popular Mechanics Vol. 125, No. 5 (May 1966), pp. 82-84, 230, and Bill Hartford, “A Rip-Roarder…with Rattles,” Popular Mechanics Vol. 129, No. 2 (February 1968), pp. 96–98, 208; John Ethridge, “OHC in a Tempest,” Motor Trend Vol. 18, No. 1 (January 1966), pp. 46-49, and “Sporty Specialties: Cougar & Firebird,” Motor Trend Vol. 19, No. 5 (May 1967), pp. 34-37, 41-42; “Pontiac Tempest Sprint,” Car and Driver December 1965, and “Pontiac Le Mans Sprint,” Car and Driver February 1967, reprinted in Car and Driver on Pontiac 1961–1975; “Pontiac Tempest Sprint & GTO: It’s Still….Six for the Money and Eight to Go!” Car Life May 1966, reprinted in GTO Muscle Portfolio 1964–1974, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1998); and “A Brace of Birds: The Sprint and the 400 from among Pontiac’s Five Firebirds,” Car Life August 1967, John Ethridge, “Fire Breathing Bird…first of the spring from Pontiac,” Motor Trend Vol 19, No. 3 (March 1967); “Firebird Sprint: The Sensible Supercar,” Cars December 1967; Steve Kelly, “How Do You Say ‘PFST’?” Motor Trend Vol. 19, No. 7 (July 1967); “Look What They’re Doing to the Firebird Now,” Car Life April 1968; Jon McKibben, “Fitch Firebirds: With the Corvair market diminishing, John Fitch finds another car to improve,” Road & Track April 1968; and “Pontiac Firebird Sprint,” Road & Track June 1967; and Sergio D’Angelo and L’Editrice Dell’Automobile LEA, “Pontiac Firebird Hardtop Coupe,” World Car Catalogue 1969, all of which are reprinted in Firebird and Trans-Am Muscle Portfolio 1967–1972, ed. R.M. Clarke(Cobham, England: Brooklands Books, Ltd., 1998).

We later updated the article to note the passing of Malcolm McKellar, based on information from Richard Lentinello, “RIP, Mac McKellar,” Hemmings Daily, 2 May 2011, blog.hemmings. com, accessed 15 June 2011; and Paul Stenquist, “Malcolm McKellar, Pioneer of the Pontiac Overhead-Cam Engine,” New York Times 3 May 2011, wheels.blogs.nytimes. com, accessed 15 June 2011. We confirmed McKellar and DeLorean’s dates of birth and death via the Social Security Death Index.

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