Pontiac GTO Forum - View Single Post - Exaust backfiring
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post #51 of (permalink) Old 03-31-2019, 08:05 AM
Lemans guy
 
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So think of it this wat CJ....total advance and when it comes in are “unrelated” for the moment of the discussion.

Total advance we know is centrifugal +Base and is the most important number......so if it keeps advancing to 4 thousand RPM etc, where it stops is the most important number,...let’s say it stops at 40.....

Now subtract your base, say you had 10, you now know that have 30 degrees of centrifugal advance in the distributor,....your base should then be set at 6......30+6=36......springs have no say in this......

Now if your vac can is pulling 25, I see that all the time by the way, ditch it and get The right vac set up, depending if you are running HEI or not.

I can give you those specifics if you don’t already have them.

You can change the vac can in the car. It is two screws and a little finesse, but easier to do it on the bench.

If your total is way too high, then you have to add a bushing or change the weights and center piece or a combination.

Springs are last, once all this is right then you can experiment with different springs, and they cannot go over your total advance, they just adjust WHEN that total comes in.
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