Thread: 30 degrees of advance at idle?

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Originally Posted by pnut

I was reading a very good article which made sense to me which I will use when tuning my SBC with Qjet (I think follows what Denny recommends, I'll let him comment on that):
http://www.73-87.com/7387garage/drivetrain/hei.htm

With the above setup, it will yield 30 degrees of advance at idle, that sounds very high. I have not tried it yet, just seems very high.

I have bought the Crane kit and installed it, but have not run the engine yet.(I just discovered my NEW China-Ebay HEI's vacuum advance canister diaphram was broken).

Your link does NOT work.

Tried the link again and it worked this time. Good article! Read my first sentence below.

30 degrees BTDC at idle is very excessive unless you are checking the timing with the vacuum advance connected to full manifold source at the time.

Your timing (both initial and Total mechanical) is checked and set with the vacuum advance disconnected and plugged.

The Total Mechanical (initial plus the built in mechanical advance) should not exceed 40 degrees. You will see figures above 40 degrees if you have the vacuum advance hooked up when checking.

That confirms what I thought, thanks.

First set timing to about 12-14 with no vac advance, then add in the vac advance and adjust to about 14-16 additional degrees. Of course both of those numbers are dependant on each engine, but that is my starting point. And I DO plan to use manifold vacuum (i've read so much on the subject and finally decided that is the best way to do it for my engine).