Heres my set-up, 383 (500Hp 510TQ) t-56, L/Ts and 4 inch exhaust.

Carb is a 750 cfm mighty demon.

Problem, 2 years ago, I built the 383 for it, had it dyno tuned, and it ran awesome, no hesitiation what so over although that was with a automatic.

I let gas sit in the carb over winter, although Id started it a couple of times during winter.

Last year it had a major bog, you would floor it, it would hesitate until about 2500-3000 RPMS, then slam you into the back of your seat. I called barry grant tech. support, they said its probally gummed up, so rebuilt it, so I ordered up a rebuild kit and did it. I started from scratch with jetting. Ran a little worse. So i got the dyno sheet, and returned the jetting to what they did (Jets are :P=78 S=87)

Now when its idleing, and you wack the throttle, it revs nice and sounds like its all there. When in gear, it does the same thing, hesitates until it reaches 2500-3000 RPMs and then its got tons of power. It makes 11 LBs of vaccumm at idle, but has a 3.5 Power valve in it. Could that cause it?

More specs: squirters are 31's Ive regasketed it, put ned accelerater pump diaphrams on, ...I just dont know what to do... HELP!!!!

 

hi, i have been done this more than once this with customer cars. it goes back to the gas we get these days shelf life is only 2-3 monthes now. anyways your problem is in the front metering block take it apart nothing to be scared of and clean all the holes and passages more than likely you got some gumed gas in there . the only thing i can tell you to do is add stabil to your gas when you know the car will sit for awhile . hope this helps

 

i take it you soaked the carb in carb cleaner for at least a few hours? I let mine soak for 24 hours. if you dont have access to allow your carb to soak for awhile, then get a few cans of carb cleaner and spray thru the metering block like hell and blow high pressure air thru all the pasages and spray again. if it ran good before you parked it, the above person, I believe to be correct. I really dont know ****, but!!!! up untill the last few years i have done things correct and have not been lazy. and thing have run so much better. good luck. If you had the same problems before you parked it, check the primary squirters and jets. I've been away from this for some time and may be way off. so good luck. Curt

IF BEFORE: you parked it, it backfired thru the carb the power valve may be blown. But i have had blown power valves that have not cause that much of a problem. Also check float level, maybe the primary float is stuck. but that would make it run very rich or lean at idle.

 

your real just seem pretty rich. a big difference from the primary jets. but all i have had is Holleys. Are your primary squarters working well? Are your primary jets clear?
Just double check everything till someone that knows what their talking about answers you. If your in my shoes: I'm working on my car in the garage and need answers NOW!!!!
Good Luck.

 

did you replace the accelarater diaphrams? also when you took it apart did you clean all the passages. btw just for info on me im 48 been working with carbs since i started working on cars in 1982 and still work with carbs so i mite just know a thing or 2 . as for the jeting the reason they has such a big rear jet is becuase of the way this demon is designed . it can be a wonderful carb for wide open power but can be made to run well on the street. good luck