In the past I've noticed when playing around with my idle mixtures using wideband lambda, that if you adjust the idle screws too lean, you'll get cooling problems. In non stock engine it can be quite difficult hear or measure when you are too lean at idle. I've helped several guys to get rid of overheating by opening the idle mixture screws a little.
I expected that idle advance would have an impact to cooling, but I've run msd dizzy in my Mustang already long time with quite a bit initial advance.
In my Pantera I had to focus on dizzy after gear pin issue. I have a stock one converted to Pertronix. I'm not sure where it was originally set at, but after fixing the issues I ran it at 10deg initial and 26 mechanical (13L slot) and used ported vacuum. Did not want to run more than 36deg total with closed chamber heads.
Lo and behold the idle temps wanted to begin creeping. Running the both fans in my fluidyne kept temps in control, but if I forgot the manual fan, it wanted to get hot. Don't recall what the (original, but separately grounded) gauge showed, but I was clearly scared about overheat with needle way to the right. Tried adding little fuel at idle, but didn't help.
Took the dizzy out again and limited the travel in the 13L slot so that I could run about 14-15 degrees initial, 36max total mechanical and ported vacuum. Changed the springs to lighter ones as well to get the max mechanical earlier.
I knew to expect improvement to idle temps, but I was still surprised how it did not want to heat much above 160deg while idling. The thermostatic fan never switched on, because it was not needed...
And feels happier overall with more initial and light springs. Better acceleration and less hesitation off idle. Like it a lot.
Cheers,
Janne
Original Post