I'll take some pics this week. It's been hacked up before I got the truck so some off it has be blocked off but the theres still some vac lines going to the cruise control witch isn't hooked up to the carb. Also how much vacuum should a healthy tuned in 350 make?
There's a few vac lines that should not be messed with and should be kept in perfect working order such as transission lines, distributor vacuum advance, some pull-offs, A/C, etc. Some of the mechanics that work on the newer trucks will have a better idea of those than I do.
But...
Not to sound ***holish but as much vacuum as it can muster. It all depends on cam, cam timing, lift, compression, intake style, etc. New crate engine w/mild cam should make about (or at least) 18"-20"Hg easy, more is better. 29.92"Hg is absolute lowest reading possible with a vacuum pump at sea level (Just not on an engine) (useless information to know and tell). The higher you are in altitude the lower it will be however. Over a mile above sea level ...good luck. Just kidding, the readings will be lower however, due to the thinner air. Fewer molecules of air equals less air pressure (barometric pressure), this includes negative pressure (vacuum -Newton's third law - all forces between two objects exist in equal magnitude and opposite direction-). More negative pressure allows better atomization of the air/fuel mixture as it enters the air-stream through the venturi. Simply having good vacuum does not guarantee success however. Air pressure pushes the gas out of the bowl in the presence of negative pressure; a lot of times the gas will be considered as being sucked out, but factually that is not the case. Plug all the vent holes to the carb bowl and try to start the engine, won't happen, the vacuum is there but no air pressure is available to push the gas. But I digress,
Tune the engine with a vacuum gauge to the highest reading it will muster.
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