Quote:
Originally Posted by DanEC
It shouldn't pose any problems at idle but where you do have to be careful is in a highway cruise situation with a fast centrifugal advance curve. Cruising at 2500 rpm with 36 to 38 deg inital and centrifugal advance all in, and 18 to 20 deg vacuum advance can cause some motors to develop a miss or repetitive light stumble from basically firing too early before TDC. My old, aluminum head BB Chevy developed this problem and I had to modify the vacuum can to limit total vacuum advance to about 10 eg which fixed the problem.
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I hope you meant 6-8 initial. The only problem I've ever seen from having too much advance at cruise speed is a surging situation. Initial timing, mechanical curve/total timing and the characteristics of the vacuum can (" of vacuum that it starts and at full and the total amount of advance) all have to work together. After you've tuned a few hundred, you get the hang of it.
Jim