Specs from 39-54 GMC Maintenance Manual calls for a minimum of 5 PSI at idle for a hot new or rebuilt engine and a minimum of 2 PSI at idle for a hot "used" engine. The 55-59 manual doesn't show a spec, but uses the same oil pump. I should have added that my GMC with 40,000 miles that I've put on it and unknown mileage before that, but it had a badly burned #5 exhaust valve when I bought it, idles at 425 RPM and about 12 psi in the Texas summertime with the A/C running.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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