When the printout showed that we were making 404 hp at 5,000 rpm, we started feeling pretty good, figuring we'd hit peak power right around 6,000. The next pull showed 421 hp at 5,500 and climbing. We now had the Mopar covered, but we were still looking for that 430hp goal. However, the first full pull showed that the peak was actually occurring at 5,800, and that 421 hp was about it. To this point, all pulls had been made at 36 degrees total timing. We dialed in 33 degrees and the engine responded with 427hp, still at 5,800 rpm. Optimism remained high at that point, but the 427 number turned out to be the best. The carb's jetting proved to be just about right, so we left it alone, and dialing back the timing more than 33 degrees actually shaved off a few ponies. Even the tried-and-true dyno trick of adding a 2-inch carb spacer wouldn't nudge us any further. Still, our engine had come very close to our horsepower predictions while also making nearly 450 lb-ft, besting all comers on all fronts.
ConclusionsWhile we were certainly pleased with the performance of the little Chevy, our combination was the source of some controversy around the office. Naturally, the Mopar contingent pointed out that we had more compression (barely a half point) and more cam timing (really just a narrower lobe separation at 106 vs. 108 for the Mope), though they didn't bring up their extra 10 cubes of displacement, or their biggest-of-the-test valves (2.02/1.60). The real debate was over streetability, which as you may recall, was a stated objective of the shootout. Naturally, in the interest of competition, some of us took that to mean anything that wouldn't rattle on 91 octane, but the true streetability of this engine is questionable. It idled at 850 rpm comfortably but with a notable chop and not much vacuum (less than 5 inches). A hard-core guy would motor this combo to work, particularly if he had a manual trans (and manual brakes), but he'd have to be the sort that wore his car's ill temperament like a badge of courage. Some guys dig that. However, for true sit-in-city-traffic-during-90-degree-heat reliability, this combo might prove to be a bit much for the average street guy.
We don't really consider this a failure, though. The engine isn't absolutely unstreetable, and it did make strong torque over a broad range of rpm. Still, a simple cam swap would change its personality in an afternoon. Trade off some top-end power for a broader curve with a lower peak and you could drive it cross-country. Even if the compression was deemed too high, a set of typical 0.043-inch composite head gaskets in place of our 0.015-inch steel shims would quickly shave the ratio back to around 10:1.
We'll know more about the behavior and potential of this combination as it's slated to be slid into a street/strip machine for further evaluation. Watch for it to emerge in these pages soon.
Mopar Dyno FlogFor those tuning in to this series for the first time, a recap of the small-block Mopar is in order before moving on to the dyno battlefield. The Battle of the Titans rules stipulated a budget of $2,500 and a maximum of 365 inches and a 0.030-inch overbore netted us the limit in cubic inches. We squeezed Federal-Mogul flattop hypereutectic pistons into the bores, resized the stock rods, and fitted them with with Pioneer rod bolts. Next, our pals at Johnson Machine Service (JMS) ground the cast crank 0.010-under on both sets of journals and we added a lumpy Crane hydraulic flat tappet. We then bolted on a set of Aerohead Racing reconditioned "587" 360 smog castings with 2.02- and 1.60-inch valves. For the intake we added an excellent Edelbrock Performer RPM Air Gap intake manifold along with a 750-cfm Speed Demon carburetor. Hooker 151/48-inch headers shuttled the exhaust. We even reused the stock stamped-steel rocker arms and stock pushrods to stick with our budget, though we still went around 22 bucks over. No big deal, we just had no lunch money for a couple of days.