Holley 500 off idle stumble (bad) Help.. race tonight!!

[little302]

Yes Ive had it apart, blown thru every passage. All clear...2.0 mild, on an Offy. Pulls 15 lbs vacuum, steady.... Idles perfect!! boosters are responsive as soon as the throttle is touched. 28's I think. 50 cc pump. 73 jet with power valve block off.

[engineczar]

Shot in the dark only because I recently encountered it on a customers engine. Is the gasket between the accelerator pump squirter and the carb body the correct metal one and not the fiber gasket that is used on the bowl screws? The hole through the fiber one is too small and prevents the full shot of fuel from passing through the squirter.

[steveshawjr]

get rid of the 50 cc pump put the one of a 350 on it the small one jets sound to big aswell.

from what ive been told 500s are to big for the cars the way they are

pv block like 40 something jets , 30 cc pump, 20 or 21 squirter

i got a feeling its loading up due to to much flue all at once

[little302]

No Steve

It ran great before it was parked.. @ 5 years ago... Ha Ha!! ya I know... Tank and clean that carb... I am..The jets are way big due to the power valve block off... The motor is knowhere near stock. It needs a min of 65 jets.. The blockoff( which I found when I took it apart) I do not care for. But it worked fine when we bought the motor 5 years ago. I took it to the track and turned a few dozen laps, with complete satisfaction. Everything was great.. We lost our local ministock tracks, and I recently decided to bring it back out and hit another track. Hence the problem.. Yes I know its from sitting.. I went thro the carb w cleaner and comp air.. It all blew fine. This carb was built for a 4 cylinder.. I didnt grab on off a sportsman or mod motor and drop it on.. Its coming off today and the little Earl Parker Weber is going on til I get it fixed... Thanks guys..