Originally posted by MainCap
Tech: You mean LESS spark lead, don't you?

Are you saying that I could get away with a static CR of 9.6:1 on pump gas with iron 64cc Vortec heads for a towing motor if I keep my "squish" between .035 - .040?
I should have said "normal" spark lead. The first thing that happens when a motor detonates is that timing gets pulled out of the motor. What I mean is that with tight squish, you can run pump gas and a normal load of ignition timing such as 34-36 degrees total without detonation.

I don't know if ....YOU.... can get away with it, but I have and several of my friends have. Now, we weren't building for a specifically towing application and we weren't using EGR. But we've run up to 11.0 on pump gas without detonation and I've read on several other forums that other have done the same. It's all about balancing the static c.r. with the intake closing point of the cam to achieve the proper cylinder pressure for the fuel being used.

Don't pick a cam out of thin air, call the cam grinders and tell them what you want to do. They'll help you by grinding the cam with the proper timing to achieve the highest cranking compression possible on your fuel. Be sure and tell them about the EGR. That will pollute the mixture and make a difference in the pressure the fuel will tolerate.

I've been building motors of all different kinds for over 40 years and I NEVER choose a cam without talking to the techs at Crane. I can normally get a youngster pretty close so he can budget for a spring change if necessary, etc, etc, but the final decision should be made by the professionals.