I just recently rebuilt my Holley 3310-2 and have one problem with the idle mixture adjustment. Can anyone tell me why one idle mixture screw will kill the motor and the other won't? From my experience both screws should kill the motor if turned in too far. I know that if neither screw kills the idle then it's possible there is a vacuum leak, I have experienced that but NOT only one screw killing the motor.

I'm going to pull the metering block and blow out the passages but I'm wondering if anyone else has seen this before? Does this suggest a blocked passage OR a vacuum leak (with mixture screw closed it's still drawing fuel from some place)? Where else in the carb should I look for the problem?

The motor does run fine otherwise but I'd like to solve this problem before I move on. It is a fairly mild small block with a near stock cam. It idles fairly steady (within 1"hg) at 15"hg.


Rod

 

If neither screw turned in ( or both) would not kill the motor, then it should be fuel being supplied from another source such as a bad power valve. Generally with a vacuum leak, you wouldn't be able to supply enough fuel with the screws backed out. If one screw has no effect then it may be plugged and no fuel being supplied.

 

Thanks for the reply.