*This boost pressure curve was generated on Test 4. The curve on Test 2 was roughly 0.5 psi higher over the entire rpm curve due to the greater restriction of the stock heads and cam. When we added race gas and more timing, the boost jumped to 12 psi.
|FLOW CHART |
|Valve lift ||Intake ||Exhaust |
| E/I |
|0.100 || 63 || 44 || 69% |
|0.200 || 118 || 97 || 82% |
|0.300 || 172 || 133 || 77% |
|0.400 ||223 || 159 || 71% |
|0.500 ||249 || 169 || 67% |
|0.600 ||255 || 174 || 68% |
|0.700 ||266 || 177 66% |
This head was tested on a 4.030-inch bore fixture at 28 inches of test depression.
The intake flow numbers are impressive, especially with 249 cfm at 0.500 inch of valve lift. It's also important not to overlook the exhaust side. Stock Ford heads are notorious for their weak exhaust ports, so it's clear that RHS placed extra effort toward improving exhaust flow. This not only helps at higher engine speeds for normally aspirated horsepower, but is also a key factor in how this little 302 was able to make over 600 hp. Also note how well this exhaust port flows at low valve lifts like 0.200 inch with an exhaust-to-intake (E/I) flow relationship of 82 percent of the intake. Superior low-lift exhaust flow does a better job of scavenging exhaust gas out of the cylinder, which means less residual exhaust gas in the cylinder during the next intake stroke.
Right out of the gate, this little junkyard refugee ran some pretty decent numbers with 273 hp and 319 lb-ft of torque. The guys at the Supercharger store told us to expect at least a 42 percent increase in power with the P-1SC blower, but after we slipped the belt over the pulleys and set the blower hat over the carburetor, the engine instantly responded with 408 hp-a 49 percent jump in horsepower-and 423 lb-ft at 4,600 rpm. Clearly the stock cam and heads were holding this ProCharger back from making some big power. We had anticipated that, so the next step was to pitch the stock heads and roller cam and bolt on a set of RHS 180cc aluminum heads along with a healthy Comp Cams hydraulic roller cam. Two stories in one was the result here, because this swap alone was worth a solid power bump up to 392 hp at 6,200 rpm and a torque gain from 319 to 363 at 4,400. This created a decent 1,800-rpm powerband between peak torque and peak horsepower. We also ran into a little valve-float problem at 6,300 rpm, or the engine might have made even more power. We had a stout 43 percent increase in horsepower from a couple of simple bolt-ons.