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Old 05-31-2020, 01:58 PM   #17
Charlie Stephens
Senior Member
Join Date: May 2010
Location: Southern California
Posts: 6,498
Default Re: Oil Pressure - OK

Originally Posted by Jack Shaft View Post
Vw oil pressure switch 7.5 lbs

The model a engine uses a pump, splash and gravity fed lubrication system. The pump lifts oil into the valve gallery (behind the valve cover,behind the carburetor) the gallery had dams that trap the oil which splash lubricates the valve lifters springs and guides. The oil also flows from the pools down to the main bearings and cam bores through tubes and drilled ports to the cam.Oil pump flow is high enough to keep these pools constantly full of oil,the excess drains back through the drain tube and a hole knocked in the block above the timing gear lubricating the gear teeth,this oil then drains into the dipper tray where the rod bearings are fed by dipper cups that pass through the dipper tray oil, the rods passing through the dipper tray creates the monsoon effect of oil spray present when operating

The ford system used in the model a is very effective,you do not need pressure to create the hydrodynamic principle to lift and support the crankshaft on film of oil,constant flow is sufficient to protect the bearings.Dipper rod lubrication is good to 4k rpm,any faster and the cup moves too quickly to pick up oil.

An oil pressure gauge is a novelty,when cold starting an engine you can hear the dry valve train,it takes about 15 to 30 seconds to fill the valve never want to fire up and drive an a engine,give the pump a chance to fill the valve galley before you put a load on the engine.basically let it warm up a bit at 500 rpm or so
This one closes at 4 PSI. It is a candidate to use with the "dual-temp" gauge on my '32. They have custom ones available but I didn't check them since it is Sunday.

Charlie Stephens
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