Oil pressure relief valve. Which type?
 

I'm investigating a problem on my old 21stud motor. The oil pressure would occasionally fall very low if the oil level was not kept up. I have pulled the sump and found nothing wrong with the oil pickup. So I have pulled the oil pressure relief valve and I could see it looked a bit odd, with a flat on it. This was sort of ringing a bell, as to bleed off some oil to lubricate the cam gear and water pumps. I pulled another one from a 59A motor I'm currently rebuilding and the spring was shorter, and the plunger did not have a flat on it. I pulled another one from another 59A and that was like the one from the 21stud motor.

Here's a pic:
http://i279.photobucket.com/albums/k...psabcefa38.jpg

The left hand end of the springs are level. You can see the longer spring and plunger at the top, and the flat. The other plunger looks nicely machined and in good condition. It is shorter and so is the spring.

The one in the 21 stud motor (late 37 style) is the same as the upper one in the pic, longer and with a flat.

If the upper one is correct for a 59A, any idea what motor the other one is supposed to be used in?

Mart.

Re: Oil pressure relief valve. Which type?
 

Dunno, but that longer spring has been stretched, was originally the same length as the shorter one.

Re: Oil pressure relief valve. Which type?
 

All of the plungers I've encountered had that little flat. It is designed to allow a tiny amount of oil to bypass at all times.
I have repaired Fords with the exact complaint you are now dealing with.
If you have the later oil pump installed, you MUST have as much of the oil pan baffle in place as possible. If not, going around corners, up or down hills, will allow the oil to move away from the pick up sump. There's a reason that baffle was installed originally!
If you have installed the later pump with the integral relief valve the original relief valve in the valve chamber must be blocked or it will open at its specified point and the high volume pump won't ever be able to achieve it's maximum designed output.
There is an outside chance, should you have a filter installed, that the pressure side line is not restricted down to .060".

Also,