Low oil pressure on rebuilt engine

2000 CHEVROLET S-10
147 MILES • 2.2L • 4 CYL • 2WD • MANUAL
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RBENNETTSR
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I just had the heads redone and just had a complete short block rebuild because of bottom end knock and low oil pressure when the engine warms up. which includes new pistons, rings, rods, bearings, valves, lifters, oil pump, and screen. The block, crank, and cam were machined. New everything else (thermostat, plugs, water pump, belts, hoses, gaskets, and seals). Also has brand new oil sending unit. The correct amount of oil showing on dipstick. Oil pump was primed. And yet I'm still showing the same low oil pressure after the truck warms up as if I didn't get any work done. I paid a lot to stop the knock in the bottom of the engine and I don't want the same issues to return! Please any advice is helpful!
May 11, 2020 at 11:40 AM
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STEVE W.
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What is the actual oil pressure cold and warm using a mechanical gauge not the factory parts and what oil weight are you using? If the bearings are sized correctly and it's the proper oil you should see about 35 psi at idle on a warm engine and about a 5-10 psi increase for every 1,000 rpm above that.
May 11, 2020 at 1:21 PM
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RBENNETTSR
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I'm about to get a mechanical guage so I can verify. I use the recommended 5W/30 oil required for the engine.
May 12, 2020 at 5:36 AM
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STEVE W.
  • ✓ASE Certified Mechanic
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I generally don't trust OEM gauges, some are great others are not so good and in the case of some like Ford, they have a gauge but it's connected to a switch and resistor so it reads in the "normal" range until oil pressure drops to less than 8 PSI. GM uses a real gauge but I have seen many that were way off from true pressure.
May 12, 2020 at 10:59 AM
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