Oil Pump Pressure Relief spring

[Page C.]

Re: Oil Pump Pressure Relief spring

Corvettes with this option (327/365 and 327/375) solid lifter engines were also equipped with a 80 psi oil guage this reason.

[Duke W.]

Re: Oil Pump Pressure Relief spring

The 55-60 psi spring and 80 psi gage actually started with late '63 340/360 HP engines... maybe June time frame if not later.

Duke

[Timothy B.]

Re: Oil Pump Pressure Relief spring

Thought I would add this to the oil pump pressure thread. Started my 327/365 for the final time prior to putting the body back on the rolling chassis today. This engine had been run before and the cam break-in was done months ago. This engine has a GM oil pump with the GM#3848911 high pressure spring. Today the temperature was about 60 degrees. As was the coolant and Rotella 15w/40 oil. On start-up the engine was running at 1100 RPMS and the oil pressure was 80 psi. The oil pressure dropped to 66 psi when the engine reached 160 degrees and dropped to 56-58 psi when the engine temperature reached 180 degrees. All of these temperatures were at 1100 RPMS. After about 20 minutes, the oil pressure was steady 56 psi. This looks like about a 24 psi drop in oil pressure due to the oil getting up to operating temperature. The results might be a little less on the 327/250-300 engines.

Page,

IMO, all that's happening is the oil flow through the relief passage in the oil pump cap can't move fast enough because of the thickness so the excess causes higher pressure until the oil gets heat and thins. I am sure the relief pintle is wide open.
The pressure you reported when warmed still seems high for a stock pump at 1100rpm.