How much Vacuum should I be pulling?

get one rated at 6.5.my 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.

86fn150 said:

get one rated at 6.5.my 86 351 4bbl pulls 19-21" of vac at idle(warmed up).

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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".