Vacum Problems
Thread Starter
Pro
Joined: Jun 2001
Posts: 579
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From: Pflugerville/ Colllege Station TX
Vacum Problems
I got my new engine running a few days ago and i finally got around to trying to tune it a little yesterday. My problem is i cant get it to pull more than about 4-5" of vacum at idle. I can't even get both the headlights open with any amount of reving and the power brakes are about useless. I am running a blue racer cam with 224/224 duration and .450/.460 lift. I am also running a Holley 4160 750cfm carb and a wieland stealth dual plane intake. I tried pluging each vacum port seperatly but nothing would fix the problem. Any ideas on what i should check next. Thanks in advance.
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: Vacum Problems (Jester69Stingray)
That's a hard one. I have the Demon carb and don't know much about the Holley, but you must be on the wrong port. You must have a leak around the intake manifold for your vac to be that low. I checked mine today and I had 13 lbs, I thought that was low but my brakes and lights work OK. Good Luck.
Heel & Toe
Joined: Sep 2001
Posts: 23
Likes: 0
From: PARIS
Re: Vacum Problems (Jester69Stingray)
I have an Holley 4160 600 cfm,and Edelbrock Performance. I take the brake vac on low passanger side of the carb, vac advance on front passanger side of the carb, others vac ports are blocked, and all accesories ( th350, headlights, etc...) on the intake manifold.
I think you have a hard intake manifold leak, but, if you haven't vac, or little, on the intake manifold, I like to know how the engine can run fine ?
Bonne chance ;)
I think you have a hard intake manifold leak, but, if you haven't vac, or little, on the intake manifold, I like to know how the engine can run fine ?
Bonne chance ;)
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Re: Vacum Problems (Jester69Stingray)
I can't imagine your combo is idle vaccum challenged due to cam. The L82 cam is 222/222 and .450/.460 lift. Revving the engine will actually make your vaccum go down, not up. Sounds like you could have a major vaccum leak somewhere. How does it idle? The headlights should be hooked up to the manifold vaccum.
[Modified by 79MakoL82, 6:51 PM 2/23/2002]
[Modified by 79MakoL82, 6:51 PM 2/23/2002]
Melting Slicks
Joined: Dec 2000
Posts: 2,041
Likes: 0
From: Wichita, KS
Re: Vacum Problems (Jester69Stingray)
Somehow, somewhere, you've got a major vacuum leak. Possible points are, intake at the cylinder head, intake to carb., vacuum fitting at the manifold, transmission at the modulator.
Drop by your friendly auto parts store and pick up a can of starting fluid. Swap the nozzle for one with a straw type extension. Spray the items noted above lightly while the engine idles. When the engine revs up you've found your leak.
I ended up using a brush in some areas after spraying the brush.
Last resort - If the above doesn't point to a leak, check the valve lash.
Drop by your friendly auto parts store and pick up a can of starting fluid. Swap the nozzle for one with a straw type extension. Spray the items noted above lightly while the engine idles. When the engine revs up you've found your leak.
I ended up using a brush in some areas after spraying the brush.
Last resort - If the above doesn't point to a leak, check the valve lash.
