250lbs of oil pressure, imposible?

impossible? 360 magnum. Ran the drill and the oil gauge stuck at 60 psi. Installed a known good gauge. Read 250psi. Split the oil filter. Oil is getting all the way to the rockers. New cam bearings, rod. 0027, mains .003. Original factory hydraulic rollers. Pulled the pan and pump. Relief valve is shimmied with a washer
080-.100" . Relief valve moves freely. I'm surprised the pump could even make that much pressure. 5w30 oil. I'm stumped. Is the shim the issue?
Doug

It's possible to make that much pressure since it's a positive displacement gear pump, as long as the shaft doesn't shear! And you measured it happening

Could the relief passage be blocked with debris or casting flash?

Absolutely possible. I would think it would need more shim than that but

Buddy of mine built a 440 many moons ago that only made 5 psi so he shimmed the pump up nearly solid. Still 5 psi. Discovered he forgot to put a plug back in and fixed it. Didn't take the shims out of the pump...

Fired it up and the Lee Eliminator oil filter came out from under the front of the car like a rocket with 7 quarts of Valvoline Racing 50 right behind it. He said it instantly pinned the Stewart Warner gauge.

Kevin

I doubt I’d believe it unless it happened to me........ but I had a metal shaving get caught in the relief valve in my 340....... stuck totally closed.
125psi hot idle, 275psi at rpm.

I've had the luck to buy at least three new Seal Power, maybe they where Speed Pro brand standard, maybe high volume, to many years ago to remember now, oil pumps that had the solid sided 440 bypass valve in them instead of the SB one with the holes in the sides
Let us know what you find to fix it
I drill a small hole in the cup and then a #8 sheet metal screw in that hole to pull the cup to find out if it was stuck and learned that they had the wrong valve in them from the factory

I would guess 250 would expel all the gallery plugs.

I'm a dumb ass. I assembled this pump about 9 months age. Just looked at a google pic of a pump. The service manual pic sucks. I put the core plug in backwards. The plug in that position depressed the spring approximately 1/4" + .100" shim. The spring is tensioned about 3/8" deeper than the factory position. Been doing this stuff 40 + years and still find ways o make mistakes. Fortunately I'm still smart enough not to start it until the issue is resolved.
Doug

My first 440 build would idle 75 hot and peg a 150psi guage. I ran the black mp filters to keep them from blowing off. I put at leak 5k hard miles on it like that. It never went over 6500 and i ran an extra quart for good measure.

250psi...I am impressed lol

Doug thanks for being humble and sharing your experience. This helps us all learn.

Mike

don't feel bad. i did the same thing on a 2.2 engine one time. those have the same pump relief spring as a small block.
when i fired it up, the wix filter [the 51515 standard size] and almost all the oil got pumped onto the ground.
not sure why i put the cup in backward, but i did, and i had a 1/4" shim with it, so a MESS it made.
oil pressure gauge was pegged WAY past high.

Your drill must be one heck of a good drill......

This was the first thing I thought of.. must have been a 1/2" drill motor

Thank you for following up and closing the loop.

If for some reason anyone ever asks what will happen with a 3/8" shim, we know the answer to that question!

1/2" Milwaukee. The part that surprised me is that the drill could possibly produce enough speed to provide enough volume to require the relief to even need to open.
Doug

My 3/8 milwaukee will open the relief and I test every one and I slow it way down to guesstamate
the proper speed

Got back to it last night after fixing the pump and installing the pan Sunday afternoon. It wasn't the filter that had split (Wix held 250psi). It was the oil filter plate. It bent. Straightened it out in the press. 65psi all is good. Then the distributor wouldn't seat. Appears to be a shot blasted reman unit that was in the previous 1968 318 converted to Petronix. Thought it was the O ring. Removed it still wouldn't seat down. Pulled the new Comp Cam oil drive. The distributor tang wouldn't go in the slot. The tang on the shaft was burred. A few quick laps with the file. Now they fit together. Distributor still won't seat. Dig thru my stash of small block gaskets. 4 distributor O-rings. 3 are the same, ah 1 is thinner. Apparently the early distributors use a thinner O-ring than what came in the Magnum gasket kit. Distributor fits. That was it for the night. Time for a beer.
Doug