427 Tri-Power vacuum ?

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427 Tri-Power vacuum ?

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427 Tri-Power vacuum ? - 9/10/2008 3:54:37 PM

tripowerrookie

Posts: 3
Joined: 9/10/2008
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What kind of vacuum psi should I be seeing out ot the manifold? If I test vacuum off the nipple back next to teh Distributor. If I''m not getting much at idle, what are the most likely culprits?

Thanks for any help.

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RE: 427 Tri-Power vacuum ? - 9/10/2008 6:37:10 PM

73shark

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Joined: 4/18/2006
Status: online

Welcome to the Corvette Forum.

You are probably getting a ported vacuum which is very low at idle due to it being sourced above the throttle page. You need to get a direct source at the manifold. Depending on your cam, it can range from ~10 to ~18 inches.

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RE: 427 Tri-Power vacuum ? - 9/10/2008 9:44:13 PM

tripowerrookie

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I''m getting -2psi at idle.-10 at around 2k rpm''s. Gotta chase down a leak I guess.

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RE: 427 Tri-Power vacuum ? - 9/11/2008 10:34:43 AM

tripowerrookie

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Here are a couple images of the situation

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RE: 427 Tri-Power vacuum ? - 9/11/2008 5:41:08 PM

73shark

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Joined: 4/18/2006
Status: online

Are you sure you''re getting direct vacuum from the intake manifold? Not sure the engine would run w/ only 2 inches of vacuum. I know the end carbs start to open as the vacuum decreases so they might be a source of manifold vacuum. If you truly have only 2" at idle, then the end carbs would be almost wide open.

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