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.

 

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.

 

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

 

Here are a couple images of the situation

 

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.