BBC Running terrible

[BOBNKIM]

BBC fires up 1st try, but runs like a dog. Have to feather the pedal to keep it running. NOT drivable! Water/antifreeze is always perfect, never low. Has new distributor, cap, rotor, new plugs, fuel filter, fuel pump, regulator, ect. Demon 850 carb. Blowing white smoke but no oil/antifreeze mixing and all fluids are good. Truck was running strong then started dying at stops, progressively got worse to where it is now. Can get it started right away but fouling out plugs quickly. Don't think I have any sensors, it's an old 502 BBC. Compression must be good b/c when it ran it ran awesome and it fires up quick. Carb is used but a shop SUPPOSEDLY rebuilt it and set it to factory specs for me. It's definately getting plenty of gas, regulator is holding steady. Any suggestions?

 

[bucket]

Did all the parts come before or after it started running poorly?

 

[DoubleDingo]

Fuel filter(s), plural if you're running an in-line filter and one in the carb. Vacuum leaks. Check for those. Mine ran like crap, couldn't find the issue, then one day I had it idling and was looking around under the hood and heard hissing. Found 5 of those bastards, and now have another one I can't find. I'd start with two things first because they are cheaper to fix.

 

[86 SCOTTSDALE]

Float out of adjustment?

 

[Wumbo]

White smoke is coolant. Thats odd.

Blue smoke maybe? Bad rings or valve guides would give you blue smoke and plug fouling.

 

[Wumbo]

Have you checked compression yet?