CM871 oil pressure

[Rawze]

(04-12-2018 )Brock Wrote:  When I shimmed my pump, I had a issue and still do. When I start my truck cold it will go to 60psi but warm it's under 20. I updated my oil bypass plug and spring as weĺl. No one here had any idea why........

60 cold with it shimmed is normal.

Shimming the oil pump does not cause the pressure to be higher at idle once it is warmed up. The pump simply does not have enough volume to do this at idle. If it is below 20 at idle, then check your rod/main bearings and other things that could cause pressure to fall off.