tecar442

My '67 442 has an oil pressure problem. When I start it the pressure goes to 50#, after a minute or two the pressure drops to 25#. Oil pump by pass valve, maybe? Can I run it with 25# and be safe? I just drive it, no racing, though I do have to get on it occasionally, just because. Do I need to shim up the spring in the pump or just or just replace the pump?

oldcutlass

That is normal, and depending on oil viscosity can be a bit higher or lower.

Sugar Bear

What engine do you have? Are the pressures provided at idle? What weight oil? How many miles on the engine? Does the pressure increase with RPM's? How does it sound, any dull knocking when very warm at idle? Can you get a mechanical oil pressure gauge to test it with?

25lbs. at warm idle is probably fine.

The problem with just changing an oil pump is that oil pressure problems often are related to worn bearings also, this could lead to a major project that may not be necessary.

If you drop the pan, consider pulling the front cover to replace the timing chain and both gears if not done already.

tecar442

Oil pressure at idle. Doesn't really change much when driving. Engine has less than 5000 miles, new timing gears and chain, new oil pump. 10W40 Valvoline racing oil. 40-50# of oil pressure would make me feel a lot better but if 25 is OK, I'll just keep driving it. I only put about 800 miles on it this summer because I didn't like the pressure. Mostly stock 400ci, original motor. It does make a little lifter noise, no knocking at all.

oldcutlass

What does it go to while driving at 55-70 mph?

Sugar Bear

I would be happy with 25 psi at warm idle, but not 25 psi while driving, especially with a 5,000 mile engine. Try to get a direct connection mechanical gauge and take some readings.

When does the lifter noise occur, cold, warm, hot? Is it a tapping noise?

Do you know what the crankshaft bearing clearances were when the engine was rebuilt?

tecar442

Oil pressure comes up a little when driving at highway speeds though not much above 30#. I have used a mechanical gauge, in fact two of them to obtain those readings. Lifter noise quiets a bit after startup but never goes completely away. I have filed a bit on the rocker pivots to add more preload and that did help some. If I need more removed, I'll have a machinist do it. I have no idea what the clearances were, I didn't do the rebuild myself.

oldcutlass

Sorry I misunderstood earlier, 25#'s at idle is actually very good, but 30 at cruise is a bit low. Cut your oil filter apart and see if there is any metal in there. I'm wondering like you if possibly and oil pump issue.

tecar442

I did cut the filter apart and found some very fine metal, not a lot, like dust. I took it to the guy who built the engine, he said that that amount was normal. Like I said in my initial post, maybe I need a new oil pump or at least shim or replace the spring in the existing pump. If the bypass didn't release at low pressure, it would raise pressure in the engine, right? I'm not a mechanic, just a hobbyist and I appreciate everybody's input.

oldcutlass

Your right.

Sugar Bear

Inspect and measure a couple of your main bearing clearances if you remove the oil pan. Excessive clearance between the crankshaft and the bearings will cause low oil pressure as will a defective oil pump.

Does anyone know of galley plug locations that could be inspected if the pan is removed?