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Cadillac 390 low oil pressure, help!

Started by DTBass, January 19, 2012, 08:30:27 PM

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DTBass

Ok well I have a 390 motor recently back from the engine builder.  He completed the short block and I am putting the rest of it together.  Everything is bolted on to the motor with the exception of the power steering and generator.  The distributor is also not yet installed.  With the distributor out and installing a long metal rod into the oil pump and then connecting that to a drill I was able to spin the pump and get some oil pressure.  The problem is that I am unable to get more than 30 psi.  I am using the port in the block next to the oil press sending switch, (it's in the back of the motor close to the firewall),I have checked the gauge and it is accurate, I have checked for leaks and see none,  I am using a Fram "spin on" type oil filter, and Quaker State 10W-30 Oil.  My drill is a stanley that spins at 1300 rpm according to the label on it which would correspond to 2600 rpm if the motor was turning.  I am spinning the pump counter clockwise as this is the correct direction of the distributor.  I called the engine rebuilder and he said the rebuild was staight forward and doesn't think he over looked anything.  Although the block is a 390 we used heads from a 365 motor but I don't think this would effect the oil pressure.  I'm reluctant to start the motor with this problem.  Anybody have any ideas or ever had a similar problem?  I need a direction to go in.  Thanks
1917 Maxwell
1948 Oldsmobile
1954 Chrysler New Yorker
1957 Cadillac Series 62 Coupe
1966 Mustang

Eldovert

#1
That is decent oil pressure..don't worry the motor is fine.Don't forget the zinc additive for cam break in and keep the rpm up when you flash the motor.
Cheers,Pat MacPhail

Caddy Wizard

The engines have a built-in oil pressure regulator valve.  The spring in the valve is calibrated to bleed off oil pressure above a specified amount.  On the earlier 331's, the pressure was about 35psi or so.

This sounds fine to me...
Art Gardner


1955 S60 Fleetwood sedan (now under resto -- has been in paint shop since June 2022!)
1955 S62 Coupe (future show car? 2/3 done)
1958 Eldo Seville (2/3 done)

DTBass

1917 Maxwell
1948 Oldsmobile
1954 Chrysler New Yorker
1957 Cadillac Series 62 Coupe
1966 Mustang