Thread: Holley carbs - return to idle

Is anyone familiar with holley carbs and idle return?

I have a holley projection system and the idle return is inconsistent. Sometimes it returns fine (idles at 700rpm) at other times it returns to anything from 800-1800rpm. There's no consistency in it. A blip of the throttle usually drops it back down - sometimes to 700, sometimes to 900 - again, a bit random.

The engine is (what is understand) is a stroked p76 v8.

I've added a second set of idle return springs on it. No change.

Drowned the carb in carb cleaner. No change.

Strange thing is, if its idling at say 1500rpm and I turn it off, when I fire it up again (not touching the throttle), it'll idle at 700.

Its definitely the butterfly on the carb that's staying slightly ajar, I've popped the hood and closed the butterfly and it returns to 700rpm.

Could it be the stroked engine is creating too much vacuum and holding the butterfly a bit? The idle vacuum is between 20-24 inHg.

Any help/advice would be appreciated.

I had something similar for a very long time with the 350 in my POS. Added another idle return spring, etc.

Turned out to be a coolant hose occasionally just interfering with the cable / carb linkage.

DL