Oil Pressure at Filter Port and Rear of Engine


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Aug 14, 2014
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Madison, WI
My Car
1971 M-Code Mach 1 w/408C stroker
I have always wondered about oil pressure difference when measured at the standard location at the back of the engine or at the port next to the filter. Unfortunately I don't have two pressure gauges so I can't answer that question. I measured pressures at two different occasions trying to use the stock gauge as reference but obviously this is not an accurate procedure. Everyone's stock gauge would be a bit different since over time they typically will lose adjustment. Take this data for what it is. All I can say is that the difference between the two measuring ports is not huge. I have read anything between 10 to 20 psi. I think in my engine it is less than 10 psi, but I don't have a way to know for sure.
The mechanical gauge I used is a Harbor Freight one I used when I built my engine. I don't have this one permanently installed so I had it taped to the windshield for this test. I just purchased a SPA dual gauge so I can keep track of oil pressure and temperature in one place. This will replace my current oil temperature gauge that I installed under the dash. I will keep my stock oil pressure gauge just for the sake of it.

Oil Pressures.jpg