Thread: spark knock
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Old 11-10-2009, 01:57 AM
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Re: spark knock

Quote:
Originally Posted by matt rupert View Post
--should i be using vac advance on a motor like this with low vacuum.
Uh oh.... what vacuum source are you using with this?

You must use the ported vacuum source for the distributor. This has no vacuum at idle, but develops progressively more vacuum as you increase throttle and RPM.

Ported vacuum is not affected by a radical camshaft, like manifold vacuum is.

If you are using a manifold vacuum source, you are getting the inverse of what you want. Manifold vacuum will give you full vacuum advance at idle, with progressively less as the throttle is opened, which cuts power. This also may be producing the spark knock.
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