Small-Block Chevy Bolt-Ons - Quick-And-Easy Bolt-On 70 HP

We bolted the heads on in a matter of minutes, and the direct result was a major gain not only in peak power but also in average torque at every rpm point. At the peak, the 395 ci fell just short of 500 hp with 490 at 6,000. Yahoo.

We bolted the heads on in a matter of minutes, and the direct result was a major gain not

Peaks And Averages
While the dyno graph clearly shows the power increase when we added the camshaft and the cylinder heads, we went one step further and have included the peaks and averages for horsepower and torque from 2,500 to 6,000 rpm. With the bigger cam, Test 2 and Test 3 extended the power beyond 6,000 rpm, but we did not include those numbers to maintain a fair comparison. Note that while the cam improved the average torque by 4 lb-ft, the head swap with the cam added a whopping 27 lb-ft of average torque. That means the torque gained an average of 27 lb-ft at every 100-rpm point between 2,500 and 6,000 rpm. That's an amazing power gain, and this was against an excellent ported head as evidenced by the flow bench test numbers. A 71hp gain at the top is fun to claim on the Internet, but the real point here is the tremendous gain in average power. It's hard to point to just the cylinder heads because that 27 lb-ft is the combination of the Comp hydraulic roller and the AFR heads. But that push is what you'll feel in the seat of your pants.

In addition to the hydraulic roller, we added a set of Comp Cams Ultra-Gold aluminum 1.6:1 roller rockers to help pump up the lift. Since these heads will increase airflow well past 0.600-inch lift, we could have used more lift, which might have pushed this small-block above 500 hp.

In addition to the hydraulic roller, we added a set of Comp Cams Ultra-Gold aluminum 1.6:1

Final Test
Rather than rely on just engine dyno numbers, AFR's Mamo also wanted some final dragstrip numbers. If you recall, the Corvette ran 12.82 at 107 mph in its original condition. The return run up at Bakersfield was more than a little disappointing, since the Corvette didn't run any quicker, but the trans automatically upshifted in Drive at a way-too-low 5,400 rpm. This prevented the engine from taking advantage of that additional horsepower between 5,000 and 6,000 rpm. Plus, with the additional torque the new heads contributed, the Corvette now spins the tires on the launch, something the previous combination did not do.

Clearly, there is more to gain with additional track tuning, and just because the engine makes more power doesn't always mean the car will run quicker. This illustrates just how important all the little details are in terms of getting the car quickly down the track. The launch, chassis tuning, tire pressure, shift points, and proper engine tuning all affect how well the car runs down the track. It's all part of the game if you want your car to run quicker. Clearly, Migletz has more work to do, but the Corvette is on its way to the low 12s.

Click here for the small-block dyno chart.

By Jeff Smith

Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!