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Blowby? Oh my!


datsun dreamer

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Not realy sure what you would call this......So im driving to a stop sign..Downshifting and i'm holding the clutch as i am approaching the stop and i notice a small cloud of blue smoke! I start to drive and it goes away(or i cant see anything!) Truck doesn't over heat and drives as normal(but does leak oil!) Should i not be concerned or is it a sign of something about to happen! any info. greatly appreciated, Thanks,Jason.

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Depending on how hard you were breaking to a stop it is possible to force the oil in the pan up to the front. If the crank was spinning fast like during a down shift the oil could be thrown all over the cylinders and would be too much for the rings to handle, resulting in a prolonged puff of smoke. If this is the case, don't worry. Additionally this oil spray might have found it's way past the baffles and into the PCV tube and be sucked into the intake. Again resulting in smoke.

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Over filling the oil can aggravate this too.

 

A racing engine can eliminate this by extending the pan lower (if possible) or by welding baffles to prevent the oil from moving forward, or in any direction and a windage tray can be bolted to the main bearing caps to provide a shield to prevent oil from splashing directly on the spinning crank. The ultimate way is to have a dry sump set up. Oil is continuously pumped out of the pan, or scavenged, and sent to a separate container elsewhere. Another pump supplies the motor. This keeps a minimal amount in the oil pan and away from the crankshaft.

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