03-09-2010, 09:20 PM
Join Date: Jul 2005
Total Cats: 68
stock oil pump relief valve measurements
FWIW I measured the oil pump spring
It exerts 3.55 kgf @ 5 mm of compression
= 40 lbf/in
diameter of piston = 16 mm = 0.4 in^2
pre load of spring at rest = 10mm
piston cracks open with an additional 3.3 mm ... total 13.3mm ... that's 53 psi
each mm of motion is an add'l 4 psi
The piston has a wear mark which suggests a "wide open" position which has an additional 3mm of movement. This is 65 psi.
For every additional 1 mm of shimming, it adds 4 psi.
If you add a 2 mm shim it'll crack open at 61 psi, and it'll be 73 psi at the "wide open" position.