... I think these Milodon pumps are a much better pump than the Melling IMO.

Fwiw...... for what the OP is doing with the motor, I would have used the HV pump from the start.

I use a HV pump on anything other than stock pan engines. They have a tendency to run stock pans dry, which is never good

When in doubt, change it out
That is my motto now, I hate it when some part fails that I had doubts about using

I've heard this many times and as long as I verified that the pickup was within 3/16 from the bottom of the oil pan(through the drain plugs) on stock OEM 4,5 and 6 quart stock pans I never saw that happen
I have seen it happen on a motor with a 7.5 quart deep sump pan that the owner used the "correct' pickup that came with the pan that was right at 1.5 inches up from the bottom the oil pan It would loose oil pressure at the end of a 1/4 mile run when he let off
Murphy lurks waiting to mess with us car guys, especially drag racers

You changed the design of the oil system when you added the EDM lifters so now you have to play oil pump engineer to get the system back in balance. Engine builders do this all the time. Pushrod oiling, bushed lifter bores, wide bearing clearances, etc. all change how the oiling system works. The more internal leaks in the engine then the more volume you need to pump. The problem with the HV pump is that sometimes it is too much volume so then you have to use a softer spring to blow off the volume inside the pump.

If you can access the relief spring with the engine in the car then go ahead and run it with the HV pump and see where you are at for oil pressure both hot and cold. If the high pressure is too high then you can change back to the softer spring. I mix and match springs and pumps all the time to get the correct combination for the engine. I use a little fixture to measure the spring force so I know which one to use.

I got the engine running. My hot oil pressure is less than 10 lbs. at 1500 rpm. Pressure is 20 psi at 3000 rpm. I changed the oil to a 10w 30 and the pressure rose about 5 psi hot. Evidently I have an internal oil leak. But am at a loss where it might be or how to find it. Looking for suggestions or how to proceed. I have oil flow out of the rockers both sides and it doesn't appear to be foamy or have bubbles in it. I'm going to remove the intake today to look at the cam / valvetrain

I got the engine running. My hot oil pressure is less than 10 lbs. at 1500 rpm. Pressure is 20 psi at 3000 rpm. I changed the oil to a 10w 30 and the pressure rose about 5 psi hot. Evidently I have an internal oil leak. But am at a loss where it might be or how to find it. Looking for suggestions or how to proceed. I have oil flow out of the rockers both sides and it doesn't appear to be foamy or have bubbles in it. I'm going to remove the intake today to look at the cam / valvetrain

I can’t imagine it having any oil pressure to speak of if a plug were missing.
And one would need to be really loose........ like ready to fall out before I think it would have that much affect on the pressure.

If you’re still employing the factory style through-the-cam top end oiling, I don’t see how the oiling to the top end could be the problem.

To me, that leaves a restricted or loose oil pump pick up, a restriction coming out of the pump into the block, a restriction in the pass side oil gallery........ or excessive bearing clearances somewhere.

Hopefully priming with the intake off will reveal something.

I just had a 360 on the dyno the other day.
It has edm lifters, pushrods with holes on both ends, and rockers than can be used as pushrod oiled.
It also retains the factory through-the-cam oiling(double oiling to the top)......... and plenty of side clearance between the rocker pairs.

Stock replacement type pan....... after several back to back pulls the oil pressure was still 30psi@1000 rpm.
About 65psi@6500 with Driven BR 15/50.

Both sides are fed by the oil going to the #4 cam journal, and through the cam when the holes in the cam line up with the holes in the bearing.
Both sides are at the same point in the flow path.

There would have to be a restriction to the feed on the one side to not have equal oiling to the top end.

My thought at this point is....... the #4 cam bearing is toast(as well as maybe a couple more), and may have wadded up some babbitt and stuffed it in the feed holes going to the top...... and the one side is essentially blocked off.

I did find some bearing material [ that is what it looks like] in the oil on the pass sde head. I guess i'll find out when i get it apart.. thank you for your help! Would or can an incorrectly installed cam bearing cause low oil pressure?

I did find some bearing material [ that is what it looks like] in the oil on the pass sde head. I guess i'll find out when i get it apart.. thank you for your help! Would or can an incorrectly installed cam bearing cause low oil pressure?