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How much Vacuum should I be pulling?

1842 Views 5 Replies 5 Participants Last post by  daremoe
I'm rebuilding a Holley for my truck and need to pick a powervalve. I don't have a vacuum gauge and won't be buying one anytime soon, no matter how cheap they are.

It's a stock 351w, 1983. Has anyone ever hooked a vacuum gauge to theirs? I'm guessing it's 14-16 inches?
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get one rated at 86 351 4bbl pulls 19-21" of vac at idle(warmed up).
only way to tell how much vacuum your pulling is to measure it with the engine running. other wise your only guessing.
get one rated at 86 351 4bbl pulls 19-21" of vac at idle(warmed up).
Cool thank you.
I have a question on vacuum as well. I hooked up a lombata sensor on the tail pipes to adjust the carb, after some messing around with it I found that at idle it had an a/f of 14:1 at 800 rpm. But once I ran it up to 2000rpm found that the a/f went up to 20:1 at part throttle cruise mode. So after jetting the carb and putting new rods and springs in, I found at 2000rpm it dropped to about 16.5-17 a/f. This is a performer series edelbrock, #1405.

Now there is one valve that is out of adjustment, making a bit of noise at idle, and I was wondering if this could cause a vacuum leak that is giving me the grief. I had a vacuum guage on it and it's pulling 14.5" at idle. Is this enough, or should i start tracking down a vac leak? I should also mention that I have a proform hei dist on it as well with the vac advance.

Thanks in advance
Altitude affects vacuum - 1" drop for every 1000' over sea level. Baseline 20".
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