Yeah, that seams really low.
I had the lower intake/head gasket vac leak, and my vac was not any lower because of it. You should be able to look at the gasket between the head and the intake, and see if it has slipped down. It took about .25" of shift in the gasket to cause the vac leak to the crankcase.
The b cam has a lsa of 107 and 224 duration. My cam has 112 lsa and 230/236 duration. I was still able to get 17" at 1k rpm, with oil (and a vac leak through the pcv). I had that 17" both with and after the intake gasket problem. My idle has never surged, even with all of these oddball problems.
Sounds to me like your problem should be elsewhere. Did you use starting fluid to check for vac leaks? Are you getting any oil in the intake? How old is the block? Worn rings will show as a lower vac reading, but probably not that low? Was it difficult to set idle? How far in did you have to set the idle screw?
I would suggest putting the vac/pressure gauge on the crankcase/pcv output. It can tell you alot.
I don't know if I helped, but I do wish you luck. I know exactly how frustrating this kind of thing can be.
jason
Yeah, that's not a typo. I put a gauge on it and it's 3" hg at idle. I put the same gauge on my 88gt in the same spot and pulled a solid 15 at idle. Apparently this is the problem w/ my car with the code 91 (system lean) keeps showing up. People have told me a vacuum leak would cause this code but I figured I would have heard hissing or noticed something. The idle on the car is pretty solid and I didn't even suspect a vaccuum leak however when I put the gauge on there I couldn't even believe it. I checked over the hoses and everything is hooked up and not leaking (the hoses running from the vacuum tree) Anybody have an idea? I'm suspecting the gasket that mates the upper plenum to the lower and probably going to replace it tomorrow. I have a b cam in the car and figured vacuum would be a little lower but this just doesn't seem right.
