Originally posted by Henry Rifle
This vacuum thing goes round and round, doesn't it?

I just pulled the spec sheet for my Chevy crate motor, a Fast-burn 385. Also, check this article:

http://chevyhiperformance.com/howto/97438/

Which, in part, says this:The vacuum advance on HEI distributors is meant to control part-throttle timing, not initial or WOT timing. As you come off idle, you get max ported vacuum, and your engine timing jumps way up. As you go to WOT, ported vacuum (and vacuum advance) drops off as mechanical advance comes in. At WOT, you have full mechanical advance and no vacuum advance. That's the way the advance curves are designed.

Can you hook the distibutor to manifold vacuum? Sure, but the timing curves go wacky.

Is this true for ALL HEI distributors? I honestly don't know - but for most of them out there today, it is.
henry, this vac. thing shouldn't keep going around and around. this thread spilled over from a thread from yesterday in which the guy wanted to know what vac. line to use. it was based on a old q-jet, carb, 1985 motor and dist. and what he was told is the setting he needs. I've all ways been talking stock. not a fast-burn 385. if i had a fast-burn 385 i probably would do something dif. but that was not the ?