Inliners International Forums General Discussion Engines high idle

hey everyone, i have a chevy 292-6 w/ a 1 barrel carb. when i start it up to warm up and after driving it revs high. i adjusted carb all the way clockwise and runs rough, cc 2 turns till smooths out and goes back to high revs. not to exp. w/ carbs does anyone know of a sweet spot on them? thanks for any info/help.

something is holding the butterfly open or you might have a vacuum leak- check hoses, vacuum advance lines, power brake hoses etc. spray some B-12 or even wd40 around base of carb and intake to head areas and other suspect places that see engine vacuum- if it speeds up theres the leak.

That's the first thing to check.
Also possible: fast-idle linkage from the choke won't relax - unhook it to check.

thanks i will try those things tomorrow, appreciate info. thanks

i sprayed some wd-40 on throttle linkage and backed the bolt (stopper) on the back of carb and that slowed the idle down. which port does the vac line from distributor go to on carb? thanks for any info.

What year is the truck and is this carb the original one? Is it a rochester monojet ot a model B? The monojet started comming out about 1968 or '69. Without knowing what stage of smog controls you have I cant tell you if vacuum advance sees manifold vacuum all the time (connection is below throttle butterfly or on manifold) or if it dont see vacuum at idle (connection is above throttle butterfly at a special vacuum advance port).
I was always so anti-smog that I would plug this special port and try to find a full time vacuum source and hook to it and run the vac. advance as a presmogger would be, I would set the timing as high as the fuel would allow (maybe 10 degrees). I used the light weight advance springs in the centrifical advance ( even sometimes used ONLY ONE spring)-I would then have to limit the amount of travel the vac. advance vacuum linkage had (used a nail in the plunger arm's slot. Never knew what the total advance was- didnt care, it had a lot snappier responce, thats what I wanted. Just watched out so it didnt ping too much. Now this was probably 1975ish and I dont remember if I had to them run premium fuel or not, back then gas was so cheap it didnt matter much. Also does the throttle shaft have much play? On a older truck the shaft or the casting can get sloppy and have a vac. leak right there-try shooting some spray at each end of the throttle butterfly shaft too.

hey edski, thanks for the info. the truck is a '77 chevy 3/4 ton crew-cab that had a 454, then the p/o put in the 292. i've been told the 292 is an '85 w/ the roch. monojet. i just had it rebuilt a couple months ago cause the mech. said it was sucking air and he couldn't set the timing. thanks again.

hey everyone, would anyone happen to know where the vacuum line from distributor to the carb goes? looks like in the manual that it goes on the pass. side of carb but not sure which port( there are 2 together). also have another problem. when starting to drive i go to step on the gas and it spits and sputters and eventually starts to smooth out, also causes the trans. to upshift/downshift. would this be vacuum related? any info would be greatly appreciated, thanks.