Small Block & Big Block Chevy Specific - Small block woes...

Ive been trying to get this tuning dialed in on this 383 for months and it seems to be everchanging. The oddest thing will be this:

Problem 1:
Today i started the car and fuel pressure was about 6.5 psi which is exactly where i want it. The air/fuel is stoichiometric and the car is running great. I turn it off and start it again about 1 hr later. Fuel pressure is about 3.5 psi and both fuel bowls are completely full. Car is running very rich and begins to fowl plugs. In the between time nothing has changed. What can cause this? I can adjust the car to raise fuel pressure and lower floats and it will be fine for a while. The the psi will be too high and floats too low. I just cant seem to figure this out.

Problem 2:
Timing is dialed in and car idles and revs with no backfiring. Yet when i attempt to drive it it backfires very badly and runs very poorly. How could a load being placed on this motor change things?

Thanks guys

maybe the needle valves aint seating and its dumping fuel in the carb, hence the low fuel pressure, try seeing if you can borrow a carb from a friend

or maybe the regulator is bad, try calling whoever manufactured it and tell them your problem

I had a simillar problem with my 383. Unless you have a hi-volume fuel pump that requires it, take the regulator out of the loop and try it, this will tell you if it's the regulator. Also take the bowls off and spray them out good and spray the needles and seats with carb cleaner. I used to have to do that every once in a while because the carb would just all the sudden start dumping fuel and want to flood out.

Ive been trying to get this tuning dialed in on this 383 for months and it seems to be everchanging. The oddest thing will be this:

Problem 1:
Today i started the car and fuel pressure was about 6.5 psi which is exactly where i want it. The air/fuel is stoichiometric and the car is running great. I turn it off and start it again about 1 hr later. Fuel pressure is about 3.5 psi and both fuel bowls are completely full. Car is running very rich and begins to fowl plugs. In the between time nothing has changed. What can cause this? I can adjust the car to raise fuel pressure and lower floats and it will be fine for a while. The the psi will be too high and floats too low. I just cant seem to figure this out.

Problem 2:
Timing is dialed in and car idles and revs with no backfiring. Yet when i attempt to drive it it backfires very badly and runs very poorly. How could a load being placed on this motor change things?

Thanks guys

IF IT HAS A HOLLEY THE POWER VALVE IS BLOWN OR THE WRONG SIZE PUT IT BACK TO WHEIR YOU WERE WHEN IT RAN FINE AND CHECK OTHER STUFF COMPENSATING WITH FLOAT LEVELS IS NOT GOING TO FIX IT JZ

Its a 750 speed demon carb. I havent changed the jets or powervalves yet. And it ran fine with these at one time.

The motor also dieseled today when i shut it off. Seems to run great at all rpms when in neutral but when in gear it seems to spit and sputter.

Just curious to see if you got everything ironed out?

i had the same problem twice once it was the regulator was sticking inside(holly) so i hit it with a wrench and it fixed it the next time i put a berry grant 280 on and it was just barley pushing fuel to the carb but the bowels were full the pump just keep un priming its self

Yeah i got all those problems fixed. Its been on the road for about 2 weeks now. Im still tweaking the carb but its been running great lately. Turned out to be mainly valve lash, they were way too tight. Also the timing was off and tad and i also swapped to a different carb. Runs much better now though. Well enough to outrun a c5 z06. HAHA, i guess i should be taking it easy but its so hard.