First Guess: You have a big "Fist-sized" oil pressure sending unit just above the oil filter. They're NOTORIOUS for inaccurate gauge readings. They can fail and show high pressure, they can fail and show low pressure, they can fail so that the gauge is "all over the place", and they can fail so that they leak. Sometimes, when you unscrew them, they're really heavy because they're full of oil. They're not hugely durable, my truck has had the original, plus three replacements.
Many parts-store catalogs show the WRONG REPLACEMENT PART. What they call for is too large, doesn't fit properly. The "correct" aftermarket sending unit has a green paint stripe on the end.
Oil Pressure Sending Unit--TBI V-8 dash gauge C/K
www.automotiveforums.com
Correct sensor (with green stripe by hex end), incorrect sensor with NAPA part number, and the heat shield
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O'Reilly's
BWD S4320 seems to be the correct one. It has a silver case, and green paint around the end with the electrical connector. The NAPA / Echlin crossover from that number is
OP6729. AutoZone sells it as
PS150, but verify all these part numbers before leaving the store.
I stumbled upon an aftermarket version of the heat shield. CarQuest doesn't have a photo, but the description sounds good. P/N S4049S.
My '88 K1500 5.7L does about the same for pressure readings, and has ever since the rebuild. However, this is with a "stock" oil pump.
About 13--15 psi hot idle in gear. I'd prefer more pressure, but not so much that I plan to do anything about it.
The next SBC I build will get a "big block" oil pump. Essentially the Melling M99HV-S kit, except I bought the pieces separately. Use with TBI/Vortec V6 or small-blocks requires trimming the windage tray.
www.summitracing.com/parts/mel-m99hvs
Free Shipping - Melling High-Volume Oil Pumps with qualifying orders of $109. Shop Oil Pumps at Summit Racing.
www.summitracing.com
