In an earlier article on the Crosley Hotshot, we mentioned that it carried a groundbreaking engine with an overhead camshaft. That got us thinking about another innovative OHC powerplant that arrived over two decades later.
And when we saw a Montero Red Pontiac Tempest with the distinct “OHC 6 Sprint” badging at the 2021 Goodguys Summit Racing Nationals a few weeks ago, we figured now was a good time to tell you about it.
The OHC Inspiration
And just like he did with the aforementioned GTO and Vega, DeLorean looked to Europe. He noted that cars like the Jaguar E-Type were powered by engines running overhead camshafts. This OHC design not only reduced the number of moving parts in the engine, it improved valvetrain performance and allowed for better valve sizing and spacing, which often meant a wider usable rev range and improved flow.
Always the engineer, DeLorean sought to develop a similar overhead cam engine that could create V8 power with less cylinders, in a lighter, more compact package.
Enter the Pontiac Overhead Cam Sixes
Starting with the basic engine architecture from Chevy’s inline six, Pontiac engineers pretty much reworked the entire thing. In addition to an all-new iron engine block, the Sprint 6 had a unique cylinder head that put a single, large 1.920″ intake and 1.600″ exhaust valve in each combustion chamber.
The camshaft, fuel pump, oil pump, and distributor were all driven off a fiberglass-reinforced Gilmer belt—a considerable innovation for the time. That arrangement also resulted in the Sprint 6’s signature ribbed timing belt cover that pops over the engine.
It’s also worth noting that the Pontiac OHC isn’t an interference engine, meaning that a broken or stretched belt wouldn’t necessarily result in contact between valves or the piston, avoiding catastrophic damage.
And it gets even more interesting when you look at the Sprint 6’s valve cover. It completely housed the single overhead camshaft within integrated journals, and the whole thing fit directly atop the cylinder head and valves. For valvetrain service, you disconnected the belt and removed the entire assembly just like a traditional valve cover.
Pontiac OHC & Sprint 6 Performance
It’s important to note that, while they all had the same overhead cam design, only the performance variants of the Pontiac OHC inline sixes got the “Sprint” name.
Base-trim OHC sixes were equipped with a single one-barrel carburetor and made around 130 horsepower. Sprint sixes benefitted from a hotter cam, Rochester Quadrajet, and a few other enhancements to push engine output well north of 200 horsepower.
In top fighting trim under the hood of a 1967 Firebird, the Sprint 6 made 215 hp. For comparison, the Firebird’s base 326 V8 was making 250 hp that same year. At its peak, the 1969 Sprint 6 topped out at 230 hp.
Famed tuning shop Royal Pontiac even offered a hop-up kit for the Sprint motors and, when tested on the drag strip, that extra performance could easily put you into the 14s.
The End of the Pontiac OHC Sixes
Despite some growing pains (oil starvation on the valvetrain being one of the biggest), these motors were showing that they could be capable and reliable performers. Yet, Pontiac only produced its OHC six engines from 1966 to 1969.
Why the short run? It was probably due to a confluence of issues, including mechanics’ unfamiliarity with the OHC design, high development costs, cheap gas negating the need for efficiency, and the overall perception that V8s offered inherently better performance (and to be fair, at that time, they did).
Though it’s fun to wonder what Pontiac’s overhead cam engines would have evolved into, given more development time. Perhaps the Sprint sixes would’ve propelled Pontiac through the gas crisis of the 1970s better than its nascent turbo V8? Perhaps an overhead camshaft engine could’ve turned the Fiero into the Ferrari fighter it should’ve been?
Regardless, these OHC Sprint engines are a fascinating footnote in Pontiac’s history—so at your next car show or cruise-in, be on the lookout for these powerplants under the hoods of first-gen Firebirds and 1966-69 Tempest/LeMans models.