Nitrous vs Cylinder Heads - Bolt-Ons Vs.The Bottle

We requested 58cc combustion chambers that combined with the flat-top pistons (with valve reliefs) to produce a static compression ratio of 10.25:1.

Since we had mocked up the heads previously on the motor before dyno testing, we were able to simply remove the stock heads and install the AFR 185s on the dyno. The AFRs required different length pushrods, but otherwise bolted right in place using new Fel-Pro 1262 intake gaskets.

Once installed on the 331, the AFR 185s increased the peak power from 347 hp and 398 lb-ft to 450 hp and 446 lb-ft. At 6,000 rpm, the AFR heads improved the power output of the 331 stroker by an amazing 125 hp.