low vacuum
low vacuum ok still trying to figure out whats wrong with my car after the cam install. ive narrowed it down to vacuum problems. i put a vacuum guage on and im reading only 5 to 10 at idle. a coworker is telling me that it should be more...less with a bigger cam but more than than. normal stock is 17 to 22. i checked the vacuum straight off the intake and at one of the lines. its the same reading.
ive had problems with it running rich and every time i take it to tune he tunes it and it goes back to rich at idle.
it looks like with the less vacuum its dumping more fuel in.
another coworker thinks i used the wrong size pushrods. i used hardened 7.4s same as stock. he is saying the valves are too tight, because of the pushrods being too long, and not opening right and as a result less vacuum.
any input on this? comp 236/244 .580 on a 112. mods are in the sig. should i have gone with 7.3s?
ive had problems with it running rich and every time i take it to tune he tunes it and it goes back to rich at idle.
it looks like with the less vacuum its dumping more fuel in.
another coworker thinks i used the wrong size pushrods. i used hardened 7.4s same as stock. he is saying the valves are too tight, because of the pushrods being too long, and not opening right and as a result less vacuum.
any input on this? comp 236/244 .580 on a 112. mods are in the sig. should i have gone with 7.3s?
Low and steady vacuum can be caused be retarded (cam or ignition) timing. That's a lot of duration on your cam, which will cause a low vacuum reading. With the valves being open longer, and more lobe separation, it won’t pull as strong of a vacuum.
What does the needle look like? Steady, fluctuating…
What does the needle look like? Steady, fluctuating…
Last edited by 2002 SS #476; Dec 14, 2006 at 10:03 AM.
Originally Posted by 2002 SS #476
Low and steady vacuum can be caused be retarded (cam or ignition) timing. That a lot of duration on your cam, which will cause a low vacuum reading. With the valves being open longer, and more lobe separation, it won’t pull as strong of a vacuum.
What does the needle look like? Steady, fluctuating…
What does the needle look like? Steady, fluctuating…
Alot of your reading is going to depend on RPM, what rpm was the car idling at? Was it a steady RPM or a back and forth RPM (like at my house)? Seems like people with cams around 750-900 rpm read anywhere from 9-11. When bone stock I think its around 15-20. I dont see how he can tune it, then it just goes back rich. that just doesnt make any sense to me.
Get a PR length checker and try that, Make sure you dont have any leaks, Maybe the TB is cracked to far open, or the hole isnt drilled to large. Just a couple things to check...
Get a PR length checker and try that, Make sure you dont have any leaks, Maybe the TB is cracked to far open, or the hole isnt drilled to large. Just a couple things to check...
Last edited by Z'mnypit; Dec 14, 2006 at 10:38 AM.
