Pressure is not as important as flow..........basically. You can have too much of either. Generally engines which are expected to see higher rpms are generally set up with a little more clearance than grocery getters or cruisers. The general rule of thumb is that you need 10 psi of oil pressure for each 1,000 rpms. With most engines you are going to exceed that when idling, which is good. The reason for the 10psi per 1,000 rpm is that as rpms increase, so does centrifugal force. You need an additional 10 psi to overcome those centrifugal forces. You could actually have pressure, but no flow , so your guage would show good pressure but you have no flow or reduced flow.......which is bad. Basically 5,000 rpms needs 50 psi.
Too much flow can pump all the oil out of the pan and if a particular engine doesn't have good return flow, the valve covers fill up and the pan is empty. Also too much flow can create windage around the crank as the oil flows back. Many people like to put high volume or high pressure oil pumps on their engines. An engine can only flow a certain amount of oil. Usually the amount of bearing clearance is the limiting factor. The oil can only flow when there is an avenue for it to flow and bearing clearance USUALLY is the determining factor......hence the video. Now it is possible that in some engines there are other restrictions in the oil passages due to their size or shape. Sometimes its the way the system is designed......ergo the order in which the components receive oil. By that I mean whether the crank receives oil first or the cam receives oil first and then the other components feed off of them. Most people consider a "priority main" as the best set up. That means the main bearings receive oil first. Most factory engines aren't priority main systems. As I mentioned earlier, people believe that a high volume or high pressure oil pump will cure their problems. Lets face it, with millions of Chevy engines out there, sometimes changing the pump has helped someones problem. The basic point is this. If the engine cannot flow more oil, then adding a high volume pump will only allow the bypass in the pump to open farther and you use HP to pump the oil in a useless circle. If your engine has sufficient oil pressure at all rpms, then a higher pressure pump will use additional HP and basically accomplish nothing.
On the 500 Cadillac engine I'm building, its known that the last two cylinders in the block are usually problematic at higher (above 5,000 ) rpms because they are the last to receive oil. Builders are learning to use some aftermarket cam bearings that have a groove on the outside and a second hole that is clocked to a position where it provides the best "wedge" to the camshaft journal. This is why I suggested looking to see what things may be available for your Chevy Big Block that may be better than the original stuff. Also, on my block I started at the oil pump mount and radiused the steps in the machined passages and bought a gun drill that I could run thru the oil passages and open them slightly. Maybe it will help, and maybe it won't but I definitely cleared out any cast in obstructions and made the passages capable of flowing even if the bearings will be the ultimate decider of actual flow.
Different people will recommend different bearings and different clearances. Clevite and King are well known. I would comb the manufacturers website and see what they recommend before listening to anyone else. The question you asked about which flow rate was best. The higher the rpm you are turning the more flow you need, but you have to decide whether less flow is better when 99% of the driving is crusing. So actual clearance will be an individual choice.
Thanks for the info
