Volume IX, Issue 1, Page 36

HEADS-UP

Reher-Morrison Racing Engines' David Reher and Darin Morgan answer your questions about cylinder heads or anything else concerning your racing engine building problems. Remember who you're are dealing with so no soft-ball questions.

1/8/07

I have a Chevy 468 big block with Brodix 2 plus heads, stefs aluminum oil pan and a high volume Melling oil pump pn# M-77hv.

My question is I noticed that my oil presure flutuates when in high gear (7000 rpm) lowest point 40 psi. I have 65 psi at idle hot.. I am thinking it is cavatating but why?

Jim Oliver
New Lenox, Illinois

Jim,

This scenario is all too common. Incorrect mind you, but very common none the less. When an engine is in the high rpm ranges and on the long haul in high gear the oil has a tendency to pool in the back of the block, lifter valley and valve covers leaving less oil in the pan. With less oil in the pan the windage from the crankshaft can actually blow the oil away from the pick up causing cavitation. This is why we use windage trays fastened to the main studs on ALL of our wet sump Super Series engines. Oil cavitation can happen even if you use a windage tray but do so in conjunction with an oil pan that is not designed well. You also need to make sure your sump screen in not to far from the bottom of the pan. For these and many other reasons, we prefer to specially design our oil pans with louvers and panels to prevent windage cavitation and cavitation caused by oil moving away from the pick up during deceleration. We have yet to find an off the shelf pan that works in all situations due to varying stroke lengths and engine speeds. Many oil pans need some work in order to perfectly tune them to a specific engine combination. Sometimes this problem can be fixed by using an AcuSump, running more oil or optimizing your oil return back to the pan. Oil return is something that most people take for granted and never give a second thought.  In some cases we go to extremes by installing external #8 lines in the back of the heads and block in the lifter valley then route them down to the oil pan. That way the oil can not pool in the heads and block.

I hope this answers your question but if it doesn’t, you know where to reach me.

David Reher asked Darin Morgan to answer this question because it is his area of expertise.

Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Visit our web site at http://www.rehermorrison.com


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