Enough Vacuum.....??
Thread Starter
Racer
Joined: Nov 2005
Posts: 410
Likes: 1
From: Amherst NH
Enough Vacuum.....??
Im Finishing up a TT home build and I am concerned with the vacuum numbers I'm getting. Keep in mind this hasn't seen the tuner yet and the idle is rough if barely there. But with a little pedal work I can hold an idle and I'm only seeing 10-11 in/hg @ 900 rpm. I've checked for leaks. Ran 10psi into the manifold with air compressor and no leaks from the back (or anywhere else). All air lines have been checked as well with no leaks. I'm running 317 heads and a custom grind TT cam. Thoughts?? I'm running AEM Tru boost but also checked with analog vacuum gauge run straight to manifold outlet to verify and they match.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Low vacuum readings after a cam is correctable with tuning---You can fix all the issues like idle speed---hunting--surging dying and dying coming to a stop
To me the biggest issue with a large cam is that your power brakes require vacuum to work correctly- Even on old school cars the lowest acceptable number has been between 10-12 inches---So yours should work fine----I had a LS1 with 10 inches at idle--on the street it was OK---But with aggressive road racing driving using the brakes a lot it would get low and the power brakes did not work very well--
Depends on your car's intended use----But all engine related issues again are easily correctable with proper tuning--
To me the biggest issue with a large cam is that your power brakes require vacuum to work correctly- Even on old school cars the lowest acceptable number has been between 10-12 inches---So yours should work fine----I had a LS1 with 10 inches at idle--on the street it was OK---But with aggressive road racing driving using the brakes a lot it would get low and the power brakes did not work very well--
Depends on your car's intended use----But all engine related issues again are easily correctable with proper tuning--
