I am working with a buddy on his heavily customized early eighties Jeep. Decent cam, Holley carb, MSD everything, headers, bIg stall convertor, big rear end, etc..

Anyway, idle performance was very poor, stalling all the time, very rough idle, even a high idle speed didn't help it. After playing with the carb (floats, mixture) I bumped the timing up a bit. Was 18 initial and now probably in the low twenties. Did it by feel and ear as well as with a Full Advance timing light. Really, really, improved the Jeep, but now at around fifty or so, at steady speed, it "bucks" a bit. Detonation? That was my thought and I can back off on timing, but I wanted to see what others thought.

It has vacuum advance hooked up. The Jeep bucked more with the advance disconnected than connected. Hence my confusion.