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248 oil pressure issue


Guest Tadp
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I have a 39 buick with a 248 straight 8. My problem is I had low oil pressure (20 cold, 5 or less warm idle) so put in classic oil pressure gauge to be sure then pulled the pan (no metal), cleaned the screen, put a 3/8 spacer on spring and found what I thought was my problem. The pot metal oil pump gear cover was warped letting oil pressure bleed by. So I flattened and sanded cover plate and reinstalled. Reinstalled pan and put in 30wt non det oil. Fired it up and had 75 psi cold 25 ish warm. Thought I was sitting pretty. After 30-40 miles of driving oil pressure slowly lowered to about where it was originally before I pulled the pan. Engine runs good. Never makes any knocking noises. Could that pot metal cover have warped again that quickly with the good oil pressure had after the fix? Looked for a 1941 cast oil pump gear cover but could find one. Pump gears are new. If I had bad bearings why would I have gotten that good oil pressure then lose it that quickly.

Anyone have any other ideas? Or notice anything I may have missed?

Thanks

Tad

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Welcome to the forum

You can join the '39 Buck team  http://forums.aaca.org/topic/207201-39-buick-team-membership/

 

From 1940 a bigger (more flow) oil pump was fitted to the 248ci

The cover clearance is critical to the oil pressure. There may be link post 5 of the above link

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Tad,

You did exactly what I did to try and get some pressure.

Have you tried adding 2 bottles of STP ?

I say 2 bottles because my '40 requires 8 quarts of oil.

Double that of a new car.

And I run Shell Rotella 15-40 in mine, and I get 60+ at start up, 20 at a hot idle and about 30 when cruzing.

Mike in Colorado

Edited by FLYER15015 (see edit history)
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My '38 Special has the same problem. The previous owner, a mechanic, told me the motor was fine, something done in the rebuild (bearings set a little loose, whatever, I can't recall the exact wording) was the reason for the oil pressure. Not satisfied, I took it to another mechanic, who told me to stop stressing, that as long as the pressure increases with rpm, it's OK.

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Rotary gear pumps loose pressure over time from wear between the gear teeth & between the gear faces and the cover plate.  Significant wear is usually apparent on the cover plate which can be ground or sanded flat & smooth again to recover most of the pressure loss.  I suggest doing this first and testing it before replacing the gears.  Just be sure to use a thin gasket to minimize the clearance between the gears and the cover plate.

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