Originally Posted by MER Performance

Oil pressure has always; seemed to be open for discussion. If testing a pump, with a gauge in a bath of oil gives you a reading of 65-70 psi, you have to remember that is at the pump. The reading say at the upper oil galley at top of block will be slightly lower. This is going to come from a decrease in volume, which results in lower pressure.
If you speak with a crankshaft manufacturer or one of the engineers, they will still go by the old school method of 10 psi for every 1000 rpm. When you look at the engineering aspect from the bearing manufacturer, the theory changes. The oil and bearing along with the location and design of the crankshafts oil galley, are going to determine the hydrodynamic wedge created between the crank journal and bearing surface. Oil temperature, bearing clearance, and the straightness of the bearing bore ( Main bore straightness in block ) are going to determine how straight the crank rides on bearing. The deflection and rpm of the engine are other factors to consider when setting up bearing clearances along with the viscosity of the oil you will be using.
I have run 54 psi oil pressure in BBC at 6000 rpm, using a Schumann oil pump and having the relief set at 75 psi at the pump incorporating a external .500 relief check ball. That is with 50 wt Redline Synthetic Racing oil, now keep in mind the mains are at .0032, rods at .0026. If I was to tighten the mains up about .0005, that would have a great affect on the oil pressure over all. The oil temp once above 140 will drastically change oil pressure only due to it's flow capabilities, oil must flow and flush the bearing in order to not overheat or scuff the bearing or crank.
Running a high oil pressure not only creates parasitic drag, it excessively loads the distributor gear, cam gear, and shaft housing and bearings in the distributor. High oil pressure also creates spark-scatter, in extreme cases also add the load on the timing chain.
I'm sure all of you know; the oil has to have ample pressure for supplying the mains, rods, cam and lifters, with it's final destination of lubricating the rocker arms and cooling the valve springs. Sucking the oil pan dry and filling the top end of the engine with oil would mean the oil isn't returning fast enough or the oil pan is way too small. Crankshaft windage and pan design are also going to greatly affect oil return and if it is aerated, causing failure of bearings with air pockets mixed in pressurized oil.
So don't be set on having high oil pressure as your safety factor in a build. You could have high pressure and still wipe your bearings out or you could have lower pressure and have like new bearings the next time you freshen up the engine.

Originally Posted by Borgie

Here is a link for Schumann oil pumps. They have quite a few features melling does not. The most important one being an external bypass vs reverting the bled off oil backwards down the pickup. Mark Rinda uses quite a few of these pumps. He recommended I give one a try, so I bought the 140HV series. Specifically states it can be used with external coolers and spring oilers. Ships with a rated pressure of 72psi, however you can increase pressure to suite your needs with a spring/shim kit that Vern sends with the pump. Also had a provision for my Dan Olson oil pickup, and a copper gasket for the sealing surface where the pump mates to the rear main cap.


http://www.schumannsdynamicperforman...-oil-pump.html

Originally Posted by MILD THUNDER

Looks like a nice pump.

Originally Posted by MILD THUNDER

Mark, great info as usual. Question for you, or anyone with knowledge in this area, slightly off topic. But, what do you think of the components here in Icdedppl's shortblocks?

540ci
Mark IV bowtie block
Eagle H beams with 8740 bolts
Iron Main caps with standard bolts, non splayed
Eagle Crank 4.250
900HP 6000RPM roots blown engines.

My gut would want to go thru the bottom ends, and minimum go with better rod bolts, possibly main studs or billet caps. I personally more worried about that than the oil pressure. Is there a legit concern here?

Originally Posted by Cole2534

Why those? Just curious, Joe.

Originally Posted by MILD THUNDER

Looks like a nice pump. Price is reasonable too.

Did you fire up that 496 yet? What did you end up going with as far as clearances on the mains/rods?