I posted this question at chevelle.com but not much help there so far. Any advice from here would be welcome.
I have a 67 chevelle., 4 speed 3.55 rear 10.2:1 454,+.040, 049 heads with 11/32" stem 2.19/1.9 valves. total combustion chamber volume is 103cc with the speed pro domes and the iron heads, measured by burette.
I was running a xe268h as I was enjoying the tame idle and torque for a mostly street driven car, but detonation proved to be a problem and I popped the head gaskets on #2 and 7 cylinders. Blue fel pro permatorques and stock re-used head bolts may have been a mistake.
I am going to swap to a 282s comp solid flat tappet. I am wondering if I should retard the cam 4 degrees to reduce the bmep a little more.
With the 268h the intake closed at 60, producing a dynamic compression ratio of 8.48:1, but it rattled at about 2000-3000 rpm. limited the total timing to 34 degrees with a stop pin on the centrifigal and ran 94 octane.the bmep was peaking at 180 psi right at that rpm range according to desktop dyno. Wallace cranking calc says the cranking compression should have been 171, but it was closer to 175-180psi.
the 282s closes the intake at 67 which produces 8.04 dynamic, 160 psi cranking, and a bmep of 176-178 where it was 180 before with a peak of 180 at about 4000rpm.
I am wondering if I should retard the timing 4 degrees to close at 71
this would produce a dynamic of 7.79 with a cranking pressure of 154psi and a bmep of 174 where it was knocking with a peak of 176. would this be detrimental to performance?
thanks in advance for any input.
I have a 67 chevelle., 4 speed 3.55 rear 10.2:1 454,+.040, 049 heads with 11/32" stem 2.19/1.9 valves. total combustion chamber volume is 103cc with the speed pro domes and the iron heads, measured by burette.
I was running a xe268h as I was enjoying the tame idle and torque for a mostly street driven car, but detonation proved to be a problem and I popped the head gaskets on #2 and 7 cylinders. Blue fel pro permatorques and stock re-used head bolts may have been a mistake.
I am going to swap to a 282s comp solid flat tappet. I am wondering if I should retard the cam 4 degrees to reduce the bmep a little more.
With the 268h the intake closed at 60, producing a dynamic compression ratio of 8.48:1, but it rattled at about 2000-3000 rpm. limited the total timing to 34 degrees with a stop pin on the centrifigal and ran 94 octane.the bmep was peaking at 180 psi right at that rpm range according to desktop dyno. Wallace cranking calc says the cranking compression should have been 171, but it was closer to 175-180psi.
the 282s closes the intake at 67 which produces 8.04 dynamic, 160 psi cranking, and a bmep of 176-178 where it was 180 before with a peak of 180 at about 4000rpm.
I am wondering if I should retard the timing 4 degrees to close at 71
this would produce a dynamic of 7.79 with a cranking pressure of 154psi and a bmep of 174 where it was knocking with a peak of 176. would this be detrimental to performance?
thanks in advance for any input.