[Healeys] Archimedes and his screw

[Bob Spidell]

Hmmmmmmm ... now that I think about it ... aren't crankcases normally pressurized by blowby? Or is my PCV valve pulling a vacuum (that wouldn't be present in Healeys without the valve)? 

bs 

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Bob Spidell - San Jose, CA 


In a message dated 10/14/09 11:46:33 AM, healeys-request at autox.team.net 
writes: 


> I attribute this to the scroll seal and'slinger' working well as long as 
> you're driving fast and steady, but not so well at slow speeds with lots of 
> stops. 
> 
We should call it by its right name: Reverse Archimedes Screw... (look it 
up if you wonder how a Greek could have invented something that has become 
iconic British). 

You lose the oil when you shut off the engine, because the negative 
pressure in the crankcase, which is helping pull the oil off the screw and back 
into the crankcase briefly becomes positive pressure, which pushes whatever oil 
was on and around the screw back into the bell housing. 

That oil in turn dribbles out of the little hole at the bottom of the bell 
housing, which should have a split pin (cotter pin to the Chevy mechanic) 
hanging out of it. The split pin is there to keep that hole clear of dirt and 
debris, so that the oil can actually drain out (and on to your garage floor) 
rather than collecting and eventually "oiling" the clutch plate. 

So, as long as the car is running, it isn't leaking oil. When it stops, it 
leaks -- as it is designed to do. The more times you stop (and the greater 
the worn tolerances between your engine block and the Archimedes screw) the 
more oil you'll leak. 

Cheers 
gary 
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