carb idling

[75 C20]

hey everyone- i got a 75 c 20 with a 350, i was palyin with my carb tonight that i put on probly a yr ago now- its a edelbrock 600cfm profromer series. anyhow i was adjusting the idle down- it was bout 800 rpm and i took the ideal screw out as far as it will adjust and it wont go below 700 rpm- how do i get it to idle at about 500 or so

thanks

[Lt.Del]

That could be a number of problems:

Timing may be off.  Try advancing the timing (turning distributor counter clockwise.)  Actually, retarding the dist may decrease rpms as well.

Vacuum leak may be a culprit.  If you have a vacuum leak, you'll never get it to idle smoothly low rpms.  Take some wd40 while engine is idling and spray around vacuum lines/hoses and gaskets.  If rpms go up, you found a vacuum leak.

Carb air/fuel mixture may need to be adjusted as well.

That'll get ya pointed in some directions.

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

[VileZambonie]

It sounds like you might be stuck on the fast idle cam. Make sure the screw for the fast idle cam is backed out. On the AFB's I believe it's facing down toward the intake.

[markzepp820]

off the subject...does your truck run good with that edelbrock performer? They have mechanical secondaries and I'm guessing you have a Automatic(TH400?) I hear carbs with mechanical secondaries don't perform as well on heavier vehicles with automatics.

[usmcchevy]

he has a mucnie sm465 granny 4 speed

[75 C20]

yeah i got a granny 4 speed as usmcchevy said but yeah it runs awesome
i love it- for being pretty well stock it rocks  

[MY854X4]

So did this work? If so how do I adjust mine I have that exact problem.

[75 C20]

Quote:So did this work? If so how do I adjust mine I have that exact problem.

yeah it worked
i went to the idle screws on the front of ur carb- first i marked where they were so if got worse  i could at least put it back to where it was- i turned each of them the smae amount ang got it down to where i wanted it and with a little more playing u can git it to idle just how u want it  

[MY854X4]

You mean the two screw's on the front bottom of the carb when you say idle screw's right?

[75 C20]

yep those are the 2 screws im talkin bout- if u still have ur owners manual it should tell u how to do it in a lil more detail

[VileZambonie]

Those two screws are your idle mixture screws. Basically screw them all the way in and back out about 3.5 turns each and adjust accordingly from there.  

[MY854X4]

And what about the screw on the throttle linkage that I think control's when the second set of barrels open's. What's the stock setting on that?