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My 84 K20 has a 502 BBC, it ran strong then started dying at stops. It got so much worse it doesn't even run now. I changed all tune up componets, even put a brand new distributor on, same thing. I assumed it was the fuel injection so I took it off and put on a Demon 850 carb. STILL, same thing. It starts great, fires right up with the turn of the key, if I play with gas pedal I can keep it running for a sec but white smoke blowing out tail pipe. ALL fluids are perfect, no antifreeze in the oil. New fuel pump and regulator and definately getting fuel but running terrible. I've checked everything. It is fouling plugs pretty quick. I've changed them and also cleaned them twice. Anyone have educated guess? Pls explain reasoning too if u would.

Just a background on how it started: Went from dying at stops to dying when slowing down then trouble restarting. As long as I could feather it through with one foot on the brake, I got it home. Always starts first try just hard to keep running.When I got it up to 30+mph, it would run great! then again slowing or stopping, wants to die. It Now extremely doggish. I'm Assuming the smoke is from sitting, been working 12s so little time to mess with it. Thanks for any suggestions!
 

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Based on "It is fouling plugs pretty quick. I've changed them and also cleaned them twice", you're looking at a carb that's overly rich - way rich. First things first is to adjust the idle mixture screws - I am not familiar with Demons but assuming they're similar to Holleys, 1 1/2 turns out on each screw should be a good starting point.


As to the white smoke - normally you're looking at some kind of coolant leak into the cylinder area. If you can get it running long enough, I would check for bubbles in the radiator.


I am sure others on here will kick in a bunch of additional items but those are where I would start.
 

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What can I say, smoke comes from too much fuel, coolant getting into the combustion chamber, oil doing the same; smoke doesn't come from sitting.

A conversion from EFI to a carb is a major change in fuel pressure, so how did ou handle that?

Fouled plugs comes from too much fuel or oil. Mechanically that can come from worn valve guides and seals, bad piston rings or worn bores, cam lobes and/or lifters going away, ya know stuff like that.

If a roller cam with a mismatched distributor gear the cam's distributor driving gear could be shot. Any distributor change would not improve that condition.

If this has a TH400 it could be sucking tranny oil past the vacuum modulator, ATF makes big white clouds when burnt.

Bogie
 

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Is the block vented? If not, blow-by can build up pressure and force oil down the valve guides.

Smoke is usually black for over-rich, white for coolant leakage and blue for oil consumption, however I once had a piston with a broken ring, and the smoke wasn't blue, but white, maybe slightly grayish-white.
 

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Fouling plugs first guess for me is always : Old gas? Doesn't sound like it with the white smoke, but heck it's a PITA to do everything and then figure out it's just gas.
 
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