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Old 02-18-2012, 05:11 AM
1965tripleblack 1965tripleblack is offline
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Originally Posted by Saltfever
The reason big cams need so much initial at idle is because they are LEAN even though they can smell pig rich. Lean AFR is a very slow burn and therefore needs much more idle advance. Look at your cam card. You have a total of 69 deg overlap! (int = 37 and ex = 32.) That is a big cam that has built-in EGR! Because of overlap the exhaust gas is contaminating (i.e., LEANING) the intake and you get lean AFR as a result. Give the motor whatever it wants at idle. I suggest you weld a bung into the exhaust and buy an O2 data logger to help with tuning.

There is no magic number to give you for WOT. Every engine requires its own number and that is determined by experimentation. Look at all the suggestions so far. There are no two agreeing numbers and that is the way it should be. Every engine and environment is different. Look at all the variables like gas or E-85, winter gas, summer gas, cold morning, or hot, humid afternoon, raised compression but by how much? Look at all the suggestions and note the assorted numbers. Pick a conservative one and start testing and reading plugs. As soon as you see pepper on the insulator back off timing 2 degrees. Good luck and have fun.

For some strange reason, Comp uses 0.015" valve lift when defining valve opening/closing events on some of its cam cards. To me, it would be better if they used durations at 0.050" as well as seat-to-seat (SAE J604d) durations. Crudely extrapolating the available durations, based on the very fast flanks of this cam (Extreme Energy), yields a rough estimate of the seat-to-seat overlap value of 77 degrees.

Yup. Got one of those with bungs in both collectors.
Works great as long as you have a powered triggering device to replace points/condenser. Otherwise there's no input to read engine RPM. Although RPM not necessary, it makes tuning easier by providing a readout on 2 axes. Of course, having a good running, STABLE laptop is essential with the Zeitronix. Not so with the Innovate unit.


What does "pepper" (black spots) on the insulator actually mean? Why does it indicate too much spark advance?

Last edited by 1965tripleblack; 02-18-2012 at 05:24 AM.
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