Hi Folks,
Have 66 mustang coupe with 69 302 rebuilt with 4 barrel Holley. When timing is correct, 8 degrees BTDC vacuum is low, 12, when I retard timing vacuum climbs to correct vacuum, above 15. Adjusting carb has no effect. Any ideas.
Thanks,
Ed G

 

Verify that your timing marks are correct.

 

I am under the impression that vac would only increase if RPM increased

I am also under the impression that if you were at 8* tdc and you retarded the timing RPM would decrease and so would vac.

So my gut reaction is: you are turning the distributor counter clock wise to advance the timing...is that accurate?

Let us know what you find!

-Gun