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Old 08-22-2002, 08:17 PM   #1
Bud69CheySB
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Lack of Vacuum

Looking for a solution on lack of vacuum. I have a 69 Chevy with a 96 Lt1 Engine that has been modified and only produces around 9/10 inchs of vacuum. I was informed I need 16 inchs for my power brakes. Looking for a electric vacuum pump or ideas that would work. It's a blast to drive with out much brakes.
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Old 08-22-2002, 08:42 PM   #2
Hooter
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do u have a radical cam in it or something?. If so you should invest in a vacum pump i have seen them in the summit catalogue.
If its stock you are going to have to find the vacum leak. It could most likely be on the throttle body or on any of the other lines.
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Old 08-22-2002, 08:55 PM   #3
lofly'a
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you can get a vac. accumulator canister that stores "vacuum surge", not sure if you have enough vacuum for that though. summit and jegs carries the vac. pump. another trick but sometimes inadequate alternative is to swap in a hydraulic booster from a diesel pickup or some 3/4 and 1 ton units. these tie into the power steering pump. i've driven a few that work real good and some that really suck, as in when you're turning the wheel and braking at the same time theres just not enough pressure to supply both accessories
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Old 08-23-2002, 11:04 AM   #4
Michael A. K. G
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A *steady* 9 or 10 inches at idle indicates a vacuum leak. You should have no trouble getting up to 16 inches.

Make sure all the vacuum lines are connected and routed correctly, and that none of them are cracked or loose. Then idle the engine and spray carburator cleaner around all the intake gaskets between the throttle body and the head. Any change in idle means you found a vacuum leak. Also, if you have power brakes, try squeezing the tar out of its vacuum line with pliers, with the engine idling. Any change in idle indicates a leaky power brake booster. If you STILL don't find the problem, try disconnecting each line in turn at the intake side and plug the port, and remeasure the vacuum.

Finally, if your vacuum has regular low jumps, you may need a valve job, or your ignition system may be "missing."
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Old 08-23-2002, 11:38 AM   #5
69sixpackbee
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I have used a vacuum pump from a Caddy diesel on my race/street cars. They are wired into the brake light switch system just like the original cars had them. You can pick these up at a junk yard for a few bucks. It helps plumbing the vac into a reservoir as well to give you extra volume.
Still even a fairly decent camshaft on the street should yield at least 13 in/hg. Check for leaks. (get out the WD-40!)
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