From the fertile mind of Mickey Thompson in the early ’60s came this fascinating creation, a Pontiac V8 with twin GMC blowers and a pair of seriously crazy cylinder heads. Let’s dig in for a closer look.
Mickey Thompson (1928-1988) was one of the great innovators in motorsport—at Indy, Bonneville, desert racing, most everywhere. (Read about his wild Ford 427 Hemi here.) The rest of the automotive world is still catching up with some of his lesser known but fascinating experiments. Like this one, for example. For some years now, a few curious photos of unknown origin (to us, anyway) have been circulating on blogs and forums around the internet. They show an M/T project from circa 1962 featuring a twin-supercharged Pontiac V8 with an unusual breathing arrangement, to say the least: The intake and exhaust ports are on the same side of the cylinder heads. But there was actually some method to the madness, as we will see.
Mounted in a dragster chassis (above) is a 389/421 Pontiac V8—Mickey had a major sponsorship deal with Pontiac in those days—with a pair of GMC blowers mounted outboard and driven by Gilmer belts. This seems to be somewhere in the mockup phase, and the cylinder heads definitely appear to be new aluminum castings rather than modified Pontiac production pieces. Note: There’s an extra cylinder head on the floor at lower left in the photo that can give us a clue as to what this engine is all about.
This detail enlargement provides a better look at the M/T cylinder head arrangement. We can see that yes, the intake passages have been rotated 180 degrees so now they are on the same side of the head as the exhaust ports.
While it seems counterintuitive to jam the intake and exhaust ports together on the same side of the head in this manner, evidently there was some sensible logic behind it. By flipping the intake ports around to the “back side” of the head, now they no longer had to snake around the pushrods and the top, inside row of long head bolts. The intake ports could now be shorter and straighter with minimum resistance to airflow. In theory, anyway.
As we see it, the drawback was reduced cross-sectional area available in that portion of the head. And since the layout has never caught on in all these years, It’s safe to assume that for whatever reason, the approach was ultimately a dead end.
There was also a naturally aspirated version of M/T’s contrary V8 using a pair of Carter AFB four-barrel carburetors. Since the conventional V8’s cylinder firing sequence would create some carburetion problems with this arrangement, it’s possible that a 180-degree crankshaft, aka flat crank, was used. This would transform the Pontiac V8 into two separate-but-equal inline four-cylinder engines on a common crankshaft.
Just to show that M/T wasn’t the lone ranger on this unusual approach to engine development, camshaft maker Bruce Crower also experimented with the setup on his Chevy small-block V8 Indy car engines in the late ’60s, first in normally aspirated form, then in a 203 CID turbocharged version. (Crower called the configuration “sidedraft,” evidently.) While the engine never managed to qualify for the Indy 500, it generated plenty of attention, eventually appearing on the December 1970 cover of Hot Rod magazine, below.