How to modify your Holley Power Valve Circuit

[Tom Kirkham]

Originally Posted by Gunner

Any tips or rule of thumb on determining a starting size for the new jet? I ass/u/me you want to start some significant size smaller than stock and increase one drill size at a time.

Should the inserts be removed from the metering block for redrilling?

Every carb is different. You will need a wide band O2 sensor to get to the right size hole. It is safer to start with bigger. A quick way to see if this is what you need to do is insert a piece of wire in the PVCR to make the effective hole smaller.

In the stock Holley metering block I am not aware of any inserts in the PVCR. Of course in the idle circuit their typically is a brass insert.