White smoke out of carb

[msbaugh]

Hey guys,
Been driving my car a lot the past 2 days. 70 challenger 440 mag. This started recently and is worrying me. When I cut the engine off it makes a really nasty harsh noise and blows smoke out the top of the carb. It kinda smells like Im running rich, so ill play with that tomorrow. Hopefully its nothing internal and just timing or in need of a quick tune up. What else causes this? Bad valve seats right? Can't remember

Thanks,
Matt

 

[burntorange70]

Not sure but it kind of sounds like you are having a run one problem. Thats when the car keeps running for a sec after you turn it off. First thing I would check is timing.

 

[moper]

It may be a few things. First thing I'd do is make sure the timing is right as burnt said. If it is, pull the cap and inspect the distributor for any obvious signs of broken parts. If that's fine, go over the carb settings and make sure they are good. After that, if it's still doing it, buy a gage, pull the plugs, and do a compression test.

 

[the wall]

i think its running on or dieseling like suggested. and some times when the engine finally stops it runs the engine backward pushing carburated fuel out of the carb. timing is not the way to fix this becuase when you cut the ignition the timing goes away (no more spark) this happens from idle to high, if you retard the timing then the idle goes down and can stop this but there goes the power. set the idle down and it goes away. higher octane gas can help this to but if your not having pinging issues now then why spend the money. an over octaning an engine loses power and economy. one other possibility is if your idle circuit on the carb has garbage in the air bleed then the carb Siphons fuel into the manifold when you shut the engine off and the fuel hits the hot intake manifold and smokes up like you see it.or the carb is dripping of the main boosters from too high of float or needle and seat in the carb is leaking and residue fuel pressure leaks into the carb and it drips out of the carb

 

[a68postcar]

i wont put The Wall's quote up because he nailed it. but typically. what you are seeing isnt smoke! it is unburnt fuel...... ie, very flammable!!!!when the plugs quit firing and when it turns backward that 8 to maybe 12 degrees, if the valve is fixin to close on compression going in reverse reopens the valve and the piston is going up in the bore. what you are seeing is atomited gasoline.