"There's no free lunch"- - - -an engine with the current "thumper" cam had better have domed pistons that give a static compression ratio of 10.5:1 or better. That doesn't mean the actual compression pressure will be that high- - - -the intake valve doesn't close until the piston is WAY up the compression stroke, so what's left of the cylinder volume has to be squeezed more tightly just to get back to stock compression pressure. Basing an engine building plan on camshaft profile alone is absolutely the wrong way to go about things, and correcting someone else's blunders by installing a milder cam might make things worse if the whole engine was built initially by someone who knew what he was doing. High compression pistons and a conservative cam profile will cause detonation that will melt the tops of the pistons in very short order, and the only way to avoid the problem is to retard the ignition timing to the point where the engine has very little low end torque. The factory muscle car engines of the 1960's were built back when 100+ octane gasoline with lots of tetraethyl lead in it was available at every corner gas station.
Jerry
