<VV> Oil Pressure Release Valve

[Ken Pepke]

Unlike a fuel pump which pumps only as much volume as the engine needs, the oil pump is a positive displacement pump which pumps out a given amount of oil on every turn of its input shaft.  That piston regulates the volume of oil the engine requires by allowing a controlled amount of the pump output to return to the pan once the oil pressure has built up in the engine.  If the piston is stuck in the bypass position almost all of the oil will return to the pan leaving too little flow to build up engine oil pressure.  This will lead to failed bearings and noisy lifters.  If the piston is stuck in the other position ALL the oil will be forced into the filter and the system causing the pressure to build [quickly] high enough to burst the filter.  Don't ask me how I know what kind of a mess that makes :-(

Ken P
Wyandotte, MI
Worry looks around; Sorry looks back, Faith looks up.

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> From: "Brian" <bmoneill at juno.com>
> Date: August 29, 2011 1:29:35 PM EDT
> To: fastvair at yahoogroups.com, VirtualVairs at corvair.org
> Subject: <VV> Oil Pressure Release Valve
> 
> A friend's recently rebuilt 102 HP engine lasted only 149 miles before destroying at least one rod bearing.  In the post mortem tear down, it was discovered that the pressure relief vale in the rear cover was stuck in the open(/) down position.  (See Item 11 of the oil system diagram in  the 1965 shop manual.) What is the purpose of this valve?  What happens if it is stuck in the down position.  Could there be any tie in to the failed rod bearing? P.S. There may be more than one failed bearing--the others not yet removed.