Inliners International Forums General Discussion Hi Performance Idle Setting

I have a Holley 390 4 barrel mounted to an Offy intake on a 230 6 cylinder. I have long tube headers. It is in a 66 chevy pickup. I can't get it to idle down. I have the idle screw out as far as it will go. I haven't put a tach on it, but intend to tomorrow, but know it idles much faster than before the holley.

Anybody have experience with these who might tell me something obvious I might have missed?

The holley is new.

You probably have a vaccum leak. Check for that.
Hope this helps.

You can use starting fluid in a spray can from your local auto parts store. Run your engine & spray all around the base of your carb, vacuum lines, etc. If the engine speeds up while you are spraying the starting fluid that means you have a vacuum leak right where you are spraying. You can use WD-40 also, but that leaves a mess behind.
Good luck!

Another method to find a vacuum leak is to use a small hand held propane torch like a Bernz O Matic. Turn it on a small amount but don't light it and move the tip along areas of suspected vacuum leaks. It works the same way as starting ether or WD40.

Mike G

Another couple of things to checkout would be the vacuum advance port (i.e has it changed from ported to full vacuum with the new carb).Also do you run any sort of PVC setup (an incorrectly rated pcv will suck a lot more air through).

my 2cents...
Jeremy.

There are two screw adjustments that control the idle speed. The main idle screw is on the side of the carb where the gas peddle linkage connects to the carb. The second idle adjustment screw is on the choke side of the carb. Try loosening this screw as well. It controls idle speed when the choke is on. It could be set too high.