I have a 1988 king cobra with a 460 ci. I took it out on the weekend and noticed the oil pressure started at 80, went down to 40 while driving and when I was coming into the harbour, it was really low....around 10 psi at 6-800 rpms. The oil was changed in the fall with 30 weight omc brand oil. As soon as I saw the drop, I shut it down and checked the oil level. It was fine. Any thoughts? I read somewhere that the pressure is roughly 10 psi per 1000 rpms, but would like some fellow guys with more experience advice. Thanks in advance.
Oh boy! An OMG 460! [I had one of those!]
That 10 psi per 1000rpm certainly is a sort of a "rule of thumb".
Low oil pressure when fully warmed up is usually either a sign of leakage past (worn cam/rod/main) bearings, the engine is HOT (overheated) or the oil pressure relief valve has some crud under it, is stuck, is not fully closing , the spring is broken/weak OR you have a leak at an oil gallery plug etc.....
Before you worry about any of the above, put a direct reading gage on the engine and verify the pressures. Make absolutely sure you're not running hot (over 200 degrees....Get a cheapo Harbor Freight IR temp "gun".....point it at the T-stat housing.....they're also good for verifying riser temps....)
Then try running 15W-50, 20W-50, straight SAE40, etc oil.
Regards,
Rick
