My dad has a 1985 Chevy Blazer S10 four wheel drive with a 2.8 liter rebuilt engine. It has new rod and main bearings, and new crank shaft with a second new oil pump in it. When it starts the oil pressure is fine, but when it warms up the oil pressure drops to nothing. He has pulled this engine twice with the problem still remaining. Some help would surely be appreciated. Tad

 

has the oil pressure been tested with a real oil pressure gauge? the factory gauges are not very accurate, and it's possible that the problem is a bad oil pressure sending unit.

 

The engine show 55 psi when started, thats using a hand held gauge, but after it warms up it drops to 15 psi, and it keeps dropping. The bearings was mic. and all seems to spec. out to manufacturers recommendations. Should Dad put a high performance oil pump in this engine? He has replaced the oil sending unit also. The heads and valves have been gone through too. I'm not for sure whats left to do ????