Low Oil Pressure - 49 Cad

[FabCad]

My oil pressure appears to be low on my 49 Cadillac. At idle, the gauge reads just slightly above the low mark. With acceleration the gauge reads about midway between the low mark and halfway mark. I'm running conventional 10W-30 with a recent oil & filter change. I believe the gauge is working properly.

Any advice?

Thanks.

[Dave Shepherd]

Did this start suddenly? How fresh is the engine, not much info to work when a complex issue is posted.

[FabCad]

Sorry guys, I'm afraid I'm not too technical. What I can tell you is the following:
1. The previous owner of the car is deceased. I have no history on the car as far as rebuild, miles, etc.
2. The drop in pressure happened recently. Previously, the pressure was closer to the halfway mark on the gauge.
3. I never flushed the engine, nor have I dropped the pan. It sounds like that's where I should begin...

More importantly, do I risk damaging the motor driving it with low oil pressure?

Thanks.

[Jay Friedman]

I agree that the pan should be dropped.  In addition to what has already been suggested, some checks that might be useful are:

1. The clearances of the rod and main bearings which can be done with the engine in car using "Plastigage", a product available in auto parts stores.  Look in the '49 shop manual to see what these clearances should be.  If they exceed the maximum allowable, lower oil pressure will result;

2. Besides what Art said about the pickup screen in the oil pump, check the spring in the oil pump pressure relief valve since if has broken lower oil pressure will result;

3. An unusual possibility that once happened to me is if a crack develops in one of the 8 (4 on each side) "stands" or brackets which support the rocker arm shafts oil will leak from the rocker arm shaft and lower oil pressure will result.  To see this, the rocker arm assemblies must be removed.

[FabCad]

Thanks for the advice, all!  I'm going to start by dropping the pan (already have the gasket).  I'll let you know what I find....

[FabCad]

So I dropped the pan and found very little sludge. Replaced the pan with a new gasket and filled it 20W50 oil (formerly I was running 10W30). Drove the car and the oil pressure is back up! Seems the higher viscosity oil was the solution.