Hey guys,

Im in another dilemna here...Was doing the last of things to my scamp to get it running finally- adding oil and priming the system. But when I went to go prime it the oil pressure sky rocketed past 150 psi pegging my needle on my gauge! At first I thought it was the gauge, so i tried another that only goes to 100, and it shot way past that one too!!

The engine itself is a 91 360LA block. I did full block oiling mods including a ported standard volume meiling pump with a high pressure relief spring, all block passages to 1/2", crossover tube in the lifter gallery, stock pan and pickup tube, and some restrictors in the mains for the cam bearings. Bearings are full groove on the mains, clearances are about .002, using 15W40 Rotella oil on break in and during this prime. The engine is using hydraulic roller lifters

I pulled off the oil pan (A giant chore within itself!) and i also had a valve cover off, and all the rockers (hughes rockers) were getting oil. I pulled the pump apart thinking the relief valve may have been getting stuck, so i pulled it apart, cleaned up and made sure it was in the right way, and then put in the standard releif spring for good measure. Instead of putting the pump back in the motor i tried this- I blocked off the side that attaches to the main cap with a bolted on plate tapped for a oil pressure gauge, and then i sucked oil through the pickup while spinning the pump...once again the pump skyrocketed to past 100psi. Im thinking the concept of this test should work since i really didnt want to put the pump back in the car and have this happen to only pull it out again.

The pump itself is brand new, was inspected too..Im wondering if there is a right way to reinstall the plug for the spring? Ive been installing it with the dimple facing the outside of the pump. Im thinking of ordering another new oil pump tommorow and testing it the same way i did with this one before i put it in to see what happens, but if it reoccurs, im stumped

Does anybody have any suggestions as to what this could be? Sorry if this is long winded, and yes a new pump is the best answer, but now im afraid to take apart a new pump and port it to have this problem again, so id rather use this one if i can...any ideas on what could be going wrong? I feel like my little test helps isolate the problem to just the oil pump itself, but i could be wrong

So you're testing the pump with just an oil pressure gauge? I don't think that is an accurate way to test it as you've dead headed the pump. The cup for the relief spring should only be pressed in far enough to get the cotter pin in and no further. The high pressure relief spring was your first mistake. The second is that 15w40 oil. With .002 bearing clearance I would use 5w20.

I used a shorter cup plug on my standard oil pump pressure relief spring, it's only about half the depth. Granted I haven't run mine yet but I don't anticipate any problems. It doesn't take much on that spring to change it a good bit.

You shouldn't use synthetic for initial break in but a lighter weight oil is better. The cup should face out. After the initial breakin you can change over to synthetic and your oil pressure may come down a little.

if it is a melling hv pump they are having issue of high pressure! put 2 new pumps in last year that came straight from melling (won with contingency) and both were 110+. their answer was to use the standard volume pump, but i reinstalled my old 1 from the previous year. supposedly housing are now made out of country. if they are melling's call them and check it out. dave

Yeah but that's not the way mine came. Maybe that's the problem

Since it's been awhile since I had one apart I decided to go out to the shop and look at an old untouched factory pump. The cup faces out [ opposite of a freeze plug ], and in just deep enough to clear the cotter pin. Since the cup plug is roughly 1/4 in. deep if you were to reverse it, it would result in a considerable increase in spring pressure. FWIW my 360 holds 65 psi hot at 2000 rpm with either 15w40 Rotella or 20w50 Bradpenn and about 5 psi less with 10w30 Bradpenn. This is with drilled oil galleries and full groove mains and a Speed Pro HV pump with a MP high pressure spring. Unbushed lifter bores with Hyd. flat tappet. I just realized that there may be some confusion as to what is meant by cup facing in or out. I think of it as out since that's where the bottom of the cup is.

put vr1 10 w 30 knocked a bunch of pressure outta mine,from that break in crud 20w 50 stuff

I have a Procomp knock off in the garage I just went and dug out, it's got the cup facing in towards the spring like the Summit picture. I know my Melling did not come that way so this looks like the likely cause. I guess I'll be pulling the pan back off mine. Better now than in the car.

Just went and grabbed my new Melling HV pump out of the box.

I just primed my motor last week. 75' LA 360 with the crossover tube oil mod. I primed the pump in a vice with a drill (75-80 lbs), installed pump, then I primed the motor with a drill. screwed a oil preasure guage right in the sending unit hole first, and left the intake manifold off to make sure no leaks at the crossover tube. Also had someone turning the crank too while priming. The melling oil pump I used had the plug with the cup part facing the spring. I'm using Brad Pen 15w40 oil and had between 75-80lbs of preasure. Make sure the plug is against the cotter key as mentioned, because the deeper the plug goes in, the more oil preasure you will have. Usually the spring won't push the plug back out against the cotter key. I'll post a picture of the pump the way it came new.

If you prime the pump in a vice and don't have enough preasure you can drive the plug in deeper and install washers between the cotter key and the plug to bump it up. I do 1 washer at a time until I get the preasure I want. I'll post a picture of an oil filter that had too much preasure in my 416". If you think it's bad removing a stock oil pan while motor is in the car, try removing a Milodon oil pan with headers! Keep us posted on your findings.

Mine is a 410" stroker, with Hughes 1.6 roller tip rocker arms, EDM oil through solid lifters , Hughes push rods, Eddy heads ported by Ryanj, 10.8-1 SRP pistons, Eagle crank and H-beam rods. 540 lift Comp cam, and melling gear drive timing set. Going in a 74' Scamp.

The filter on the left had around 100 lbs preasure when cold. I was lucky I checked the filter before it blew !

I like straight 30 wt for break-in myself. For a flat tappet cam that is. I've been hearing several issues with these pumps and they all involve high pressure.
What you did with the plate and having the pump out is a good idea. I've done it on many occasions and it works so nice. This is deadheading, and that's what you want. You need to know the maximum pressure the pump will provide, that's what the relief spring does. Your other option is to remote mount the filter and run an adjustable pressure regulator that bypasses the excess oil back into the engine somewhere. Saw it on a small block in an engine competition, but can't remember which one.

hey everybody, thanks for all the input! It turns out that i had the core plug for the spring in backwards. I put in a new one just like triple threat has his pictured, and tested on the bench with the dead head method i got 90psi, tested in the car priming the oiling system i was getting 85psi. Was going to fire the car up but ran into a distributor issue that lasted until quite late, so i didnt want to upset the neighbors...gonna have it running and driving today and taking it to the alignment shop. I will let you guys know how the drive is and what my oil pressure is like!

By the way, this is supposed to be a stock volume pump, and it now has the stock volume spring in it as well

That picture is the correct way. The flat face of the cup is against the cotter pin. The recess in the cup is for the spring to sit inside. If its switched around, your gonna have a lot of pressure against the relief spring.

If you take these pumps apart, be carefull about what you " hone". Dwyane and I were just talking about a problem where someone did this and created a big issue by making a very small mistake while honing out pump passages.

Debur them, chamfer them, clean them and run them.

Pic on left is new HV, on right STD pump.