Idle mixture screw has no effect!

Posted By: polkat

Idle mixture screw has no effect! - 05/20/08 12:39 AM

Had a problem with my idle mixture screws a few days back. While working on it today to get the best idle, I have discovered that the drivers side idle mixture screw has little or no effect. The passenger side works fine. I'm thinking some kind of dirt or debrie in the driver's side circuit. Any other opinions?
Thanks!

Posted By: Pacnorthcuda

Re: Idle mixture screw has no effect! - 05/20/08 12:48 AM

If single plane manifold the entire engine may be idling on the one idle circuit (passenger in your example). YOu may also be able to richen the drive side and then crank down the passenger side and have the same effect.
You could have a blown power valve. You could have a clogged air bleed.

Is it idling rich???

Posted By: torkrules

Re: Idle mixture screw has no effect! - 05/20/08 01:00 AM

Quote:

If single plane manifold the entire engine may be idling on the one idle circuit (passenger in your example). YOu may also be able to richen the drive side and then crank down the passenger side and have the same effect.
You could have a blown power valve. You could have a clogged air bleed.

Is it idling rich???

Both screws should be turned out the same amount. Start with the screws about 1-1/2 turns out. Turn them in or out 1/8 turn at a time. If you can turn them both in all the way, then either you have a clogged air bleed, air bleed is too small, or the idle feed restrictor is too big.

Posted By: Anonymous

Re: Idle mixture screw has no effect! - 05/20/08 01:25 AM

no opinion here until you say what kinda carb you have, and any other relevant info.

Posted By: Dart 340

Re: Idle mixture screw has no effect! - 05/20/08 01:28 AM

Quote:

Had a problem with my idle mixture screws a few days back. While working on it today to get the best idle, I have discovered that the drivers side idle mixture screw has little or no effect. The passenger side works fine. I'm thinking some kind of dirt or debrie in the driver's side circuit. Any other opinions?
Thanks!

My holley had too much of the transfer slots exposed so the idle did nothing. I have a single plane manifold with a high lift cam designed to only pull 10 InHg at idle. Do a search for tuning carbs and you will find a ton of info on here.