In 1966, Pontiac was years ahead of the herd in the Motor City with a new six-cylinder engine that boasted an overhead camshaft and an innovative toothed-belt cam drive. 

Pontiac wasn’t the first American automaker to offer an overhead-cam engine, of course. Not by a long shot. The configuration dates back to the earliest days of the industry. In production cars the noteworthy proponents included Deusenberg, Wills Sainte Claire, and Crosley, to name a few. But the layout, while ultimately superior, was more expensive and complicated than the industry’s tried-and-true L-head and pushrod engines, and as the men in the gray wool suits in the Motor City liked to say ,”If it ain’t broke, don’t fix it.”

At giant General Motors,  CEO Alfred P. Sloan reportedly said, “Never be first at anything,” but the company was known to violate that dictum from time to time. In the ’60s at the corporation’s Pontiac brand, there were a number of forward-looking people, including VP and general manager John Z. DeLorean and the division’s talented engine guru, Malcolm “Mac” McKellar, two of the men responsible for the Overhead Cam 6.

Mac Mckellar’s research and development work with overhead-cam layouts at first focused on the division’s 389 and 421 V8 engines (read our feature on the Pontiac V8 here). But when a business case could not be made for a production OHC V8, reportedly, the effort shifted to the division’s inline six. At the time, Pontiac’s six was essentially a badge-engineered variant of the third-generation Chevrolet six introduced in 1962, which in turn was based on Chevy small-block V8 architecture. So from the head gasket down, the new OHC six was essentially the familiar 215 CID Tempsest pushrod six, but with a few major changes: First, the stroke was increased to 3.250 inches, which, with a bore of 3.875 inches, yielded 230 cubic inches. Next, the distributor and fuel pump drive setup was revised, and the cylinder block was skirted 2.38 inches below the crankshaft centerline, strengthening the lower end.

The single-overhead-cam top end (above) was constructed in two halves, more or less. The lower assembly was relatively conventional: an iron casting with inline intake and exhaust valves and kidney-shaped combustion chambers. The upper assembly was the departure, featuring a die-cast aluminum cam cover that doubled as the camshaft carrier. There were no cam bearings as such; the shaft rode directly in the alloy housing. The rest of the valvetrain consisted of chilled-iron finger followers with a nominal ratio of 1.5:1 acting on hydraulic lash adjusters that nested in the head—light, simple, and effective. (For a deeper dive, see McKellar’s 1966 SAE paper 660126.) Valvetrain mass was reduced by 45 percent, McKellar noted, permitting a far more aggressive valve timing strategy for increased rpm and greater output.

One totally sensible objection to the OHC layout among the Detroit carmakers was that it required a complicated, expensive, and noisy drive mechanism. Pontiac ditched the messy gears and chains and adopted a fiberglass-reinforced toothed belt, above. Developed in collaboration with U.S. Rubber (aka Uniroyal), the Pontiac timing belt was one inch wide and weighed less than 10 ounces. Of course, Pontiac was not the first to tread this ground. Pioneers in timing-belt cam drives included Bill Devin’s Panhard-Norton sports racing engine in 1954 and in Germany, the 1962 Glas 1004. But to put credit where it’s due, Pontiac developed the innovation for high-volume manufacturing, with total production of the OHC 6 eventually running well into six figures.

Pontiac introduced the OHC 6 in two flavors for ’66: a base engine with a one-barrel carburetor that developed 165 hp at 4700 rpm, and a sportier version with a 10.5:1 compression ratio, a high-lift cam, a split exhaust manifold, and GM’s new four-barrel Quadrajet carburetor (below). On premium fuel, it was rated at 207 hp at 5200 rpm and was said to be good for up to 6500 rpm. The base engine was standard in the Tempest and LeMans series, while the high-output version was marketed in Sprint editions of the Tempest and, starting in mid-’67, the Firebird, with special badging and performance equipment.

The OHC 6 got a bump in displacement to 250 CID for 1968, but then disappeared from the Pontiac lineup after ’69, replaced by a plain-vanilla Chevy pushrod 6. There was nothing particularly wrong with the OHC 6, except that customers weren’t terribly interested either way. At the time, car buyers who sought performance were opting for big, hairy V8s, and the added production cost of the OHC engine was not reflected in increased sales. That would all change just a few years later in Detroit, when overhead cams and timing belts were suddenly everywhere.