996 Turbo's AOS... where is it?
06-02-2010, 10:27 PM
#16
Race Director
I was thinking the most common reason for smoke on start up would be worn valve guides letting oil by when the engine is off and oil draining back to the sump. Then figuring the cylinders are horizontal the flow wouldn't be down the length of vavle guides since they are horizontal also.
The exhaust and intake valves are not horizontal either IIRC. They are canted so the intakes point down and the exhausts point up. That is the stem/lifter end of the intake valve is higher than the head end and the stem/lifter end of the exhaust valve is lower than the head end.
While the engine is running engine vacuum can pull oil past worn intake and exhaust valve guides and seals into the combustion chamber. It can also pull oil past the rings/piston.
Sincerely,
Macster.
06-02-2010, 10:28 PM
#17
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they will blow a huge puff of smoke if they are started, not allowed to run for long and shut off... so will just about any engine... is this whats happening to you?
