weird flooding

[sneakyfast]

Ok guys here's a weird one. Have a 383 stroker with a demon carb on it. Went out on the interstate for the first time so was up in 3500-4000 rpm range for 20 minutes (thank you 4.10 gears). Anyway, pulled off and drove the rest of the way home and everytime I sort of gunned it a second or two later the truck dies. Wait a few minutes and she fires up with a giant cloud of white smoke out the back like I flooded it.

Thoughts?

[geezer#99]

Not flooding!!
Black smoke is flooding!
White smoke is coolant!
Check your coolant level.
Could be a blown head gasket or intake gasket.

[sneakyfast]

Mm...coolant level is fine and it doesn't continually blow smoke. That said it does have this weird thing where it will stay around 200 degrees for a long time. Then for no reason it will bump up to 240 or 250 then drop back down. Almost like a sticky thermostat except I had that replaced a couple of weeks ago.

[rich weyand]

Originally Posted by sneakyfast

Mm...coolant level is fine and it doesn't continually blow smoke. That said it does have this weird thing where it will stay around 200 degrees for a long time. Then for no reason it will bump up to 240 or 250 then drop back down. Almost like a sticky thermostat except I had that replaced a couple of weeks ago.

That's low coolant, or an air bubble in the system.

Don't just check the bottle, open up the radiator and look.

[sneakyfast]

Right at the top. How do I get an air bubble out? Drain the entire thing?

[tucsonjwt]

I had a similar problem in my luxury sedan (Cavalier). It ran OK around town but on the highway it overheated. Coolant level OK, no coolant leaks, temperature would go up at highway speeds.

I read a lot about air in the cooling system, so I bled the air bleeder the Cavalier had and still had the problem. Went to a good mechanic and he said he was "100% sure that it is the radiator." He was 100% right. His diagnosis as not accurate, though. He said to check the temperature of the upper and lower radiator hoses to see if there was a difference, which would indicate a clogged radiator. My hoses had the same temperature after city driving. My theory is that the radiator was only partially plugged, so it was not a problem unless the engine was at high rpms.

White smoke does contra-indicate my guess, since that always means a coolant leak inside the engine, but you should have some coolant loss. Just a small amount of coolant can make a lot of white smoke.

I got a Spectra radiator from Autozone for $125 with 20% off and free shipping sale recently for my 83 C20 (that radiator had holes in it.) I scrapped the old copper/brass radiator for $30 so net cost was $95.

[tucsonjwt]

One more theory. if you are overheating it could boil gas out of the carb, but that would normally show up as vapor lock on hot restart.