Quote:
Originally Posted by Rocky Rotella
Sorry for the delay, Skip. The RAIII (d-port) engines peaked around 5000/3500 (hp/tq, respectively). The RAIV engines peaked around 5500/3800. So on the 400, the larger round port heads and cam caused HP to peak roughly 500 rpm higher.
The 455 engines had remarkably lower peak points, but were affected similarly. The d-port 455 engines peaked around 4000/2800 (hp/tq, respectively), while the round port 455s peaked around 4400/3200. The HO's 068 cam wasn't exactly "large" for a 455, so we might speculate that the 400 rpm difference in hp/tq peaks, could be directly related to the larger ports.
For the record, I do know that Pontiac's engineering dynos ONLY recorded only TQ numbers, and horsepower mathematically calculated from it at all points.
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a 455 with stock D-ports will stop revving at 5200 rpm with an 068 type cam. falls flat on its face. FWIW, all dynos only measure torque, and calculate HP from it using math. even the most modern. HP is more or less, a bullschit number.