Greetings fellow olds enthusiast, I’ve been off this list for a while but I’m getting back into things Oldsmobile related. I have a 71 442 convertible that I rebuilt the engine 40 years ago when I was 18. Originally I put TRW flattop forged pistons with Chrome Molly rings and what I believe were 10.5 to 1 compression, going off of memory here it’s been 40 years. Also talked to Joe Mondello at the time and installed a JM2022 cam ,C heads ,stock 400 transmission with B&m shift kit followed by a 373 12 bolt Posi. It has a Edelbrock 04b intake with factory Quadra jet carburetor. Now the issue, engine still runs good has great compression no problems with the performance, but when the engine gets up to a warm running temperature oil pressure drops off significantly. Standard rule of thumb I believe is 10 pounds per 1000 RPM. Driving around town oil pressure is fine, drive the car out on the highway for a few minutes to another town, temperature gauge reading 180 to 200° pull up and stop oil pressure drops to 5 pounds. I replace the oil pump a few years ago but it has made little or no difference. Once the temperature is up to around 200, turn off engine and try to restart , engine drags very slow and is hard to start. Engine runs and drives strong no problems ,I’m thinking oil pressure drop may be caused from bearing wear? Possibly the mains, rods, or cam bearings? I’m thinking maybe a re-ring kit is in order As long as the cylinders check out OK. A new oil pump, and cam and lifters. It’s a convertible so I don’t expect to take it to the dragstrip. But it is a rather healthy engine and a few upgrades in the performance would not bother me a bit. Any opinions on the oil pressure problem and possible upgrades would be appreciated.

 

What oil are you running? Personally, I suspect the low oil pressure is caused by excessive bearing clearances. The hard start is likely unrelated - that's a starter problem. Verify you have min 12 volts on the purple wire at the starter solenoid. If so, then it's probably time for a new solenoid and maybe brushes in the starter.

 

Cut open the oil filter, check for debris.

My prediction is the engine was machined with the bearing clearances too tight, and the engine “clearanced” itself. Either that, or sloppy machine work.

 

My thought was lower and needed the bearings replaced, new all pump while I was at it, and heat shield for the starter.

 

I’ve replaced the starter twice, the battery cables, and a new battery. Oil is 10 W 40 Castrol. Funny that it only does this when the engine is warmed up it runs fine when cold and has no trouble starting.

 

The oil will thin as it heats up. Oil pressure will naturally drop as the oil heats up. 60psi cold can easily drop to 10psi with hot oil.

You can band aid the low oil pressure by switching to 20-50 oil, it’s going to be pretty hard to start if the temperature gets below 30ish. Don’t even think of trying to start it if it’s colder than that!!

Shell Rotella 15w40 might be a good compromise.

Unfortunately, this is like putting a band aid on a gunshot wound. Most likely, the damage is done, it’s only going to get worse and more expensive to fix.

If the engine isn’t making noise, the oil filter isn’t full of debris, low oil pressure isn’t necessarily a death sentence. In my experience, if bearing wear happens slowly, and doesn’t create big chunks of shrapnel, then a engine will last with low oil pressure. However, if the engine wears fast (like running with no oil) the debris gouges bearings, which creates more chunks, creating more damage, it’s all downhill after that.

 

I’m betting your hard hot start problem is either a defective starter, or undersized cables.

Get a voltmeter, put the positive probe on the positive battery post. Put the negitive meter probe on the battery cable at the starter stud. Crank the engine, whatever the meter reads is how much voltage is being lost due to resistance in the cable. More than a couple tenths of a volt means either the cable is undersized, or the connections are less than ideal. You can do the same test on the negative cable, negative probe to the battery post, positive meter probe to the engine.

If that checks ok, the next test would be a current draw check. You need a meter that will measure hundreds of amps, your typical handheld meter won’t work. Either pull the starter for testing, or find a shop with a battery tester.

 

When you pull the oil filter make sure the spring loaded relief flap in the filter mount operates freely and is not stuck open.

 

Tried another oil pressure gauge? Mine started reading VERY low at idle, then sporadic. New gauge, issue resolved..

 

The hard start problem has been fixed, turned out the battery cables were bad.