Question for Clem Z. or anyone else regarding idle mixture screws on repaired Holley

[Joseph E.]

The problems with the Holley carb on my '66 L72 that arose after adding AV gas to the pump premium in the tank seem to be resolved for the most part. It still seems to stumble a bit though so I plan on looking at the accelerator pump and/or draining the fuel mix and replacing it with one fuel not a mix of both. What puzzles me now is the fact that my idle mixture screws on the primary metering block do absolutely nothing to affect the idle quality or manifold vacuum of the motor. I can turn them both all the way in and the engine continues to run well with no variation in sound or vacuum reading. Before adding the AV gas, the idle mixture screws were effective in fine tuning the idle quality and vacuum reading. The engine would quit if either one of them was driven all the way in but it won't do that now. A thorough cleaning of the carb with new power valves, needle and seat assemblies, metering block and bowl gaskets along with checking to be sure everything was set to factory specs seemed to clear up most of the problems except this one. What am I missing that is causing this problem? Thanks to all who responded for the suggestions offered.

Joe (45420)

[Clem Z.]

Re: Question for Clem Z. or anyone else regarding idle mixture screws on repaired Hol

The problems with the Holley carb on my '66 L72 that arose after adding AV gas to the pump premium in the tank seem to be resolved for the most part. It still seems to stumble a bit though so I plan on looking at the accelerator pump and/or draining the fuel mix and replacing it with one fuel not a mix of both. What puzzles me now is the fact that my idle mixture screws on the primary metering block do absolutely nothing to affect the idle quality or manifold vacuum of the motor. I can turn them both all the way in and the engine continues to run well with no variation in sound or vacuum reading. Before adding the AV gas, the idle mixture screws were effective in fine tuning the idle quality and vacuum reading. The engine would quit if either one of them was driven all the way in but it won't do that now. A thorough cleaning of the carb with new power valves, needle and seat assemblies, metering block and bowl gaskets along with checking to be sure everything was set to factory specs seemed to clear up most of the problems except this one. What am I missing that is causing this problem? Thanks to all who responded for the suggestions offered.

Joe (45420)

remove the adjustment screws and blow thru with compressed air and see what happens to make sure there is no dirt in the passage. make sure the throttle butterflies in the pri are not open too far and you are idling off of the idle transfer slots.