What should the vaccum gauge read at idle with a 230 duration 500lift cam on a 112? How should the gauge react throught the rpms..i'm trying to see if i have a leak...the car runs like crap. the car seems to have vaccum at around -20 but when the rpms drop real low,...the vaccum goes to around -8

 

Vacuum wil depend heavily on idle RPM, valve timing, displacement, and throttle opening. Did you install the cam at the default timing (straight up), or advanced/retarded? 230° duration at 112° LSA on a 350 should still maintain 16-20" Hg at a normal idle RPM in neutral.

If you're running a blower, vacuum indications can mean little. Furthermore, unless the ECM is using speed-density, the actual vacuum may be less of an issue than the MAF reading.

 

When my car had a vacuum leak I was reading around 15, which is down from 20. Right now I have a stock cam, but on comp cams site they say that a cam that is similiar to yours runs 17 at idle. If you want to check for leaks get some carb cleaner and spray it around the intake gasket, if the engine revs a bit then you have a leak.

 

yeah, i checked for leaks,..don't seem to have any, but when the car get's ho t and tries to stall, the vaccum goes real low like aroung 4 or 5 just before it stalls, but i guess that is normal. I unplugged the IAC, and it seemed to run better, but it still misses a little under acceleration and still wants to runa nd stall at 400rpms at idle when it gets hot.

 

just had the same promblem when she got hot the rpm got choppy and stalled . and i was running really lean. i had a 7ft vacuum hose that was rotted. $2.50. replaced i ran great at 475 rpm. get i smoke test done it is the best way to know if u have a leak.

 

smoke test?

 

They use a smoke machine and blow smoke into the intake to see where it comes out.

 

i'll have to look into that....could be a tube too