Where is this smoke coming from?

[Unregistered]

I have a 351w, t-18, d 20,....

when i downshift to slow down, a plume of white smoke comes out from underneath my bronco...right around the clutch. At no other time is there ever any smoke. I saw it after a family member was driving it in front of me to show what the bronco was doing. My question is, is the smoke coming from my clutch during the downshift?.....this is the only time it seems to happen....

thanx,

Kelly

 

[bert]

Check for any oil leaks.
I noticed mine doing something similar a while back. My engine had a lot of blowby so it was very difficult to seal up. I noticed a puff of smoke on downshift only. Didn't make a lot of sense, but it must have caused a drop of oil to hit the exhaust manifold and burn.

 

[Unregistered]

oil leak..

i have noticed a small leak dripping from the lowest spot on the oil pan. Do you think downshifting at a quiker pace slings the oil onto the exhaust pipe, or my headers, causing the white smoke? That crossed my mind too, but i thought it sounded weird as well........maybe not. My 351/t-18/d20 was all built and installed only 4000 miles ago..if that helps. and... What do you mean by "blowby?....

thanx for the help...

Kelly

 

[bert]

All engines create pressure inside themselves while running. That is where the PCV system comes in. It removes the harmfull combustion gases and fuel that naturally leak by the rings. A motor in good condition will have very little blow by. The oil stays clean longer, ususally no oil leakage, no noticable vapors out the filler neck when idling.
As the engine wears, blowby increases do to ring and cylinder wear. Valve stem wear can sometimes be an issue. The blowby pressure can get to a point that the PCV system can no longer handle it and the crankcase gets pressurized. The pressure must go somewhere, seals and gaskets start leaking oil.
A quick check of the PCV system is to idle the engine, locate the fresh air inlet for the system and plug it with your finger. You should notice a slight vacuum it the system is operating correctly.