I have been fine tuning the 451 for our Labor Day Muscle Car shootout drag race event at Brainerd Raceway. The motor used to have heavy ported iron 452 heads at about 80 cc giving a compression ratio of about 10.25:1 (depending on head gasket thickness used.) The cylinder pressure was about 150 psi. The motor now has mild ported (But still out flows the 452s) 65 cc B1 closed chamber heads and according to my measurements should be at 12.7:1. Static cylinder pressure test shows about 165 psi.
Does this sound right? It appears that there is an increase in cylinder pressure of 15 psi. My small block friends believe this to be kinda low for 12.7:.1. However the large bore of the 400 b-block maybe obscuring this and I may be right where I should be. Valve lash also affects the pressure. 165 PSI is at a warm motor lash of .028 intake .032 exhaust. Estimate of about 600 horse to the rear wheels. Hoping for about 10 flat from 3000 lb Duster. (But I’m betting a little slower. Never seem to go as fast as I hope.) I will post results after the event whether it's good or bad.
Anyways I'm playing the timing and carb adjusting games. It appears to be acting normal. The more advanced the better the motor likes at idle, but starts some high rpm crackling at 7000. (Redline is 7500 shifting at about 6800) Retard the timing and the crackling goes away but then idles a little rougher. Attempting to adjust carb to smooth motor at idle. It can get pissy with as small as a ΒΌ turn on the jet setting.
Man! Race motors are finicky.
Does this sound right? It appears that there is an increase in cylinder pressure of 15 psi. My small block friends believe this to be kinda low for 12.7:.1. However the large bore of the 400 b-block maybe obscuring this and I may be right where I should be. Valve lash also affects the pressure. 165 PSI is at a warm motor lash of .028 intake .032 exhaust. Estimate of about 600 horse to the rear wheels. Hoping for about 10 flat from 3000 lb Duster. (But I’m betting a little slower. Never seem to go as fast as I hope.) I will post results after the event whether it's good or bad.
Anyways I'm playing the timing and carb adjusting games. It appears to be acting normal. The more advanced the better the motor likes at idle, but starts some high rpm crackling at 7000. (Redline is 7500 shifting at about 6800) Retard the timing and the crackling goes away but then idles a little rougher. Attempting to adjust carb to smooth motor at idle. It can get pissy with as small as a ΒΌ turn on the jet setting.
Man! Race motors are finicky.
