truck idle problems

i have a chevy smallblock with a turbo 400 and it idles fine when in park but when you put it in gear it losses idle...and one help with what this could be

mine is doing the same thing. i have a 350 with some motor work and a 4l60e. i was told it was cuz of high compression. when i turn up the idle speed screw on the front of the carb it idles high but when in gear it idles nice and low. i hope i can get it to idle like 600-800 all the time. so ya, i need help too.

anyone got some ideas...could it be the vac thing on the transmission ...its a brass colored thing on the pass side of the trans and there is a vac line ran to it...could it be bad or does this even have anything to do with it ?>

Edited: 6/17/2010 9:36:10 AM by idrgbdy

i talked to comp cams yesterday and they said my cam is a low vacuum cam so when i put it in gear it robs all the vacuum from the power brake booster, so i can't push the pedal at all. they said i need a vacuum canister. i seen some on summit's site. he also said that if i had a holley carb, i could put in different power valves and it should idle the same all the time. but i have an edelbrock. i called them and he said i need to call back when i have all my specs in front of me: vacuum, timing, cam info, etc... but he said maybe i could just use smaller step up springs. i also have the stock torque converter but the cam specs say i can use it, although it would be best to use a 2000 stall. but fuck taking the tranny out right now. lol i wonder if my tranny has that vacuum line you are talking about on it. i have the 4l60e. i'm driving it to a show this weekend, guess i'll just up the idle speed when it's in park and it will sound good when it's in gear. lol

i dont know what cam mine has i think its stock but mabe not ..i bought this motor as is and can tell it had a rebuild mabe it was a performance build up not stock parts ...hmm neverknow till ihave to take it apart for something...i have a holley carb

start with the easiest, then work up.  just hook up your vacuum gauge up to your carb port & see what you're pulling,  adjust it if necessary.  you can check your timing (with the vacuum hose disconnected from your vacuum advance on your distributor), hell even spray carb cleaner all over everything (intake manifold, carb gasket, etc) & listen for vacuum leaks.  check all your tubes & lines for cracks/wear.  i don't know your experience level so if this sounds like i'm talking down to you or anything, please don't be offended in any way.