Pump Gas Baby!
Q. I love reading your tech Q&A. I’m hoping you can help me with my car, a ’67 Nova two-door sedan that has run a best of 11.66. It has a 383 small-block with Eagle SIR rods and cast crank, KB pistons, cast-iron Pro Topline 220cc heads with 2.02/1.60-inch valves, 64cc combustion chamber, a Howards solid cam, 0.543/0.563-inch max lift with 252/260 duration at 0.050-inch tappet lift, a Super Victor intake, a Quick Fuel Q-series 750-cfm carb, an MSD Pro Billet and 6AL, and Hooker Super Comp 13/4-inch headers. The engine has 12.2:1 compression. We estimate the horsepower to be around 500. This is a street/strip car that I run 110 octane at the track, and premium with octane booster cruising around town. All the while I’m trying to keep rpm at a reasonable level. With rising gas prices I really would like this to be a pump-gas-only motor. Is it possible to do that by moving to a larger head that has larger 2.08 intake valves but keep power levels close to where they’re at? I don’t really want to lower the performance of the car and in talking to other people they act as if it’s not possible to build a 500-plus horsepower pump-gas 383. Do I need to look at a different motor combination? This is something I’ve wanted to do for a while but cannot get a straight answer whether to make my current motor work or do something new. Your help would be greatly appreciated.
A. Tons of people out there will tell you that you can’t build good power on pump gas, and you certainly can’t run a race car on the stuff. They’ll tell you that it won’t repeat and that you’ll blow up your engine before you leave the burnout box. Well, we will have to disagree. We’ve been running race cars on straight pump gas since 1988. Many of them have been mild street engines, but three in particular have pushed cars to respectable e.t.’s and lived for years. Our first real venture into pump-gas race engines was with a Chevrolet Performance 502. Back in 1996, we took a dead-stock Mark IV Mercury Marine big-block and added a Crane roller camshaft, an Edelbrock Victor 4500 manifold, and a 1050 Dominator carb, and ported the stock cast-iron cylinder heads. This engine made 680 hp and 600 lb-ft of torque on the dyno. This was with only 8.9:1 compression! This engine ran for about 13 years and more than 1,400 runs. At this power level it produced 1.35 hp/ci—remember this number.
In the big-block world, we’re running a 524 BBC. It has some major upgrades over the original 502 with Dart Pro One cylinder heads, Dart manifold, and a slightly larger Crane camshaft that comes in at 270/276 at 0.050-inch tappet lift, 0.756/0.756-inch max lift, ground on 112 centers. With this engine we pushed the compression up to 10:1. At a mild 32 degrees of spark timing it’s producing 800 hp and almost 700 lb-ft of torque. To date this is our best power per cube at 1.52 hp.
Finally, the mild small-block in our son’s wagon is a 354 cid with a set of LT4 heads that we’ve warmed over, a Chevrolet Performance Hot camshaft, and a Chevrolet Performance LT1/LT4 dual-plane manifold. We pushed everything on this puppy and the compression is up to 11:1! This thing—with its very mild camshaft—produced 466 hp and 444 lb-ft of torque on the pump. With the very mild combination, that’s still 1.32 hp per cube.