I have a freshly built 20B with a brand new oil pump and internals. When I start the engine, I have great oil pressure readings (30-40 psi). After the engine warms up to operating temp, the oil pressure drops (18-22 psi) at idle. I am a running SPA oil pressure gauge which I am reasonably sure is accurate. I have dual oil coolers only (no mocal oil thermostat). Any ideas? it has plenty of oil and is not leaking. I dont know if I a missing something.

 

assuming your cold idle is higher than idle at operating temperature, perhaps the issue is your oil seal between the front cover and the front housing.

 

just a thought but oil does get thinner when it heats up..so maybe that is why the PSI drops.

 

Something very wrong, my 20B cold start oil pressure is 125 PSI @ 800 rpm