Since this is Car Craft and our emphasis is on budget building, a well-prepared set of oval-port heads can offer almost as much power as a big set of rectangle-port heads, as long as you're not shooting for some outrageous horsepower number. A typical pump gas 454/468ci engine should be capable of around 500 hp normally aspirated using a single-plane intake and a decent cam with even mildly reworked stock heads. We tested a set of those tiny peanut-port iron heads on our 496 back in the Mar. '08 issue ("Big-Block Cylinder Head Test") and made an awesome 595 lb-ft and a respectable 521 hp at 5,400 rpm with tiny 2.06/1.72-inch valves. By recalculating the power based on 454 ci, it looks like your engine should be capable of at least 540 lb-ft and around 475 hp. Keep in mind that this was with those peanut-port heads, so our initial estimate of 500 hp is probably conservative.
The D-1SC supercharger from ProCharger is capable of a maximum flow of 1,400 cfm and a peak boost of 32 psi, which is impressive. But in reality, for a typical street engine, boost will be limited to roughly 10 to 12 psi max. At this point we think a 45 percent power increase is likely, which takes that normally aspirated 500 hp and ramps it up to a solid 725 and bumps the torque to something ridiculous like 740-plus lb-ft. If this isn't enough, adding the rectangle-port heads will likely improve the torque more than the horsepower numbers because the larger intake ports will represent less of a flow restriction to the supercharger. The limitation will then become the exhaust side of the heads. This is why working on making the exhaust ports flow as much as possible will add power. Then all you have to do is figure out how you're going to hook all that power to the pavement. Overall, it should be a killer package that shouldn't be prohibitively expensive. I think a good business to be in for the next decade will be performance rubber because it sounds like lots of tires will be going up in smoke.
Accessible Technologies Inc. (ProCharger); Lenexa, KS; 913/338-2886; procharger.com
Just thought you might like to see a really cool '70 'Cuda.
High Compression Experiment
Gerry Hill, Eastham, MA: About 10 to 15 years ago, one of your staff members commented on building a small-block Chevy with 17:1 compression using a special cam with delayed intake closing. The fuel mileage claimed was very good. Any info on this would be appreciated.
Jeff Smith: Great question. Gerry. The man behind that idea is Bruce Crower of Crower Cams fame. Bruce is one of the performance industry's great innovators. Bruce's idea was as simple as it was brilliant. He focused on the fact that higher static compression ratios create more power from the same amount of fuel, which is why diesel engines are generally more fuel efficient than gasoline engines. The problem with high compression ratios is they require expensive, high-octane fuel to avoid detonation. Crower's idea was to modify the cam timing to take advantage of the high compression while still allowing the engine to run on lower 87- or 89-octane fuel. Crower accomplished this with a very late-closing intake valve position. Let's first look at a mild Comp Cams flat-tappet intake lobe with 239 degrees of advertised duration. This lobe opens 9 degrees before top dead center (BTDC) and closes 50 degrees after bottom dead center (ABDC). These figures are at 0.006 inch tappet lift, or what Comp defines as advertised duration. Adding the opening plus closing figures plus 180 degrees equals duration (9 + 50 + 180 = 239 degrees).