Well, I do actually understand how and why oil pressures are regulated inside of an engine, I am sure your not suggesting that I didn't, rather your giving your opinion that is contrary to mine. That is good, its always good to dig in and see why we have the ideas that we do :]

High oil pressure. I dont really higher than is needed. About 10 lbs per thousand RPM's is a good baseline for street use as well as most race applications. If your pushing 60-80 lbs of oil thru an engine at say.....2800 RPM cruise, would you say this is better or less desirable than say 35-45 lbs? I would rather have the 35-45.

Here are some things to think about:
An engine using a High Volumne oil pump, that has stock clearances in it will cause the oil to take the path of least resistance, which in many cases is the upper cylinder heads, if not restricted. When you restrict the oil to the top end, and use factory tight clearances, you cause the HV pump to build more pressure.

In my opinion, you are starting to turn your oil pump into a hydraulic pump, rather than just being the supply pump it was designed to be. Remember, without resistance to the oil pump, you will have 0 oil pressure. "Resistance" is the key word. It is all a delicate balancing act. Your oil pressure is a combination, and the sum of all your clearances in your motor.

It has been suggested over the years by the likes of Roush, Smokey, Jenkins etc that more than 10# per thousand washes the bearings and can actually allow metal to metal contact by destroying the hydrodynamic wedge that supports your bearings.

High pressure can "float" the bearings that usually leads to spinning a bearing. It also causes high oil temp as well as airation and will wear out the distributer/cam gear quickly and can cause broken distributor gear drive pins. Try for 10 lbs pressure per 1000 engine rpms.

Your concerns are not new ones. This question has been, and is still being asked by a lot of people. No one that I know, or ever heard of, has actually tested the oiling systems on engines to get the answers and documented it. It's all a big ball of opinions. Not every engine's requirements for oil are the same.

A warmed up street motor has less requirements than a high performance race motor. The bearing loads can be calculated on the rods and mains.

I've always been a little leary of the HV pumps in a street motor, with street clearances. They can be too much! It's how they are used, Don't forget why they were made in the first place....for a worn out engine to help bring the pressure back up.

The oiling system is a balancing game. It's a balance of volume, and resistance, both of which produces pressure. Somewhere, someone might know how much oil is required in volume delivery at the bearings and friction surfaces to maintain sufficient hydrodynamic and boundry oil layer. I don't know him!

First off, we know that the job of an oiling system on an internal combustion engine is to reduce friction, remove heat, and maintain a hydrodynamic and boundry layer of oil film to prevent contact of the bearing surfaces. The required volume of oil necessary has to do with several things; rpm's; clearances; bearing surface area; and bearing load. All that is required is enough oil be present to form a hydrodynamic film to keep the rod and main bearings from contacting each other.

How that is accomplished is... think of the oil film layer as a big wave with a surfer riding and sliding on it. The wave keeps the surfer from coming into contact with the ocean bottom. Boundry oil layers are similiar but they are more friction prone. This is the lubrication on the cam lifters and lobes, rocker arms...the piston's in the bore, etc.

The science of all this is extensive, and their isn't enough room or time for it here. I hope this explains SOME of it. It doesn't take massive amounts of oil to create the hydrodynamic layer. As a matter of fact if you start using large clearances, your oil volume requirements will increase. How much clearances? Another big guessing game.

Everyone has an opinion. For the street, I think that the high side of factory shop tolerances is perfect for high performance street engines. That is usually about .0025 thousandths, on the mains and rods. On a street motor, I don't think it is necessary to have different clearances on the rods and mains. That's what 3/4 shell main bearings are for. I have seen many posters in another forum report that they are using larger main bearing clearances, and smaller rod bearing clearances. This is not correct...it's backwards. A fluid under pressure will take the path of least resistance. That means if the main clearances are larger that the rods, the rods will get less oil. Usually larger rod bearing clearances are used in aluminum rods for racing motors, because of their heat and growth sensitivities. More clearances in the rods on even steel rods are used generally for cooling purposes, because the piston transfers heat from the combustion chamber down through the rod and to the rod bearing.

Also the rod journals scribe an arc and because of centrifical force they throw the oil out of the rod journals (This will cause the rod bearings to fail if not enough oil is supplied) and if you have too much rod clearance and too much oil system volume... the rings can't handle the extra oil and it goes to the combustion chamber! Hence, the need for more oil at the rods than the mains, but keep the rod side clearance in check to minimize centrifical oil losses. The mains do not have that problem. Their problem is how to supply oil to other bearing surfaces in enough quanity, and still have enough to maintain their hydrodynamic layer requirements.

A "High Pressure" oil pump, might very well be the one to use in some applications, but...... I've heard many a person complain about pumping all the oil up into the heads and the pump sucked air. You only have so many places in the upper end measured in square inches for oil to return and complete the cycle. This very well could just be a big oil curtain pouring down on the crank and rods... frothing and slowing everything down.

Those larger rotors pumping the oil require more power be transfered through the pump shaft and timing chain. It'd be interesting to see what that did torsionally to the cam and timing!!!

These are some of the thoughts I have as to why I am not a fan of high vol/pres pumps. If clearances are big, go with a high vol as a crutch, but leave the high pressure pump in the store. I would rather see you replace the bearings with new stock bearings and I am sure that you will pick up some of the worn dimension in the journals and this will for sure give you back some of the "lost" oil pressure.

Sorry this is so long. I hope no one is offended. As usual, this is JMO.