Bottom lines up front.
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I have oil pressure gauges all over the damned place and I’m here to tell you that if you don’t have a crankscraper your pump is sucking air on most left turns. That being said, there’s guys w/o a scraper that have been running their motors hard for years. I’d like to say that I have an explanation for that apparent contradiction, but I don’t.
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Modifications to your oiling system that increase it’s volume can have unexpected negative consequences.
I have a remote oil filter, aftermarked oil cooler 3.5X as large as stock, and an Accusump behind the passenger seat. Everything is connected by -10 hose, which is slightly larger then the OEM oil cooler pipes. All of that creates a lot of oil volume.
My spare motor does not have a crankscraper. This past month at VIR, Roebling and now CMP I had weird oil pressure problems where the oil pressure would go away for about 5min. It would happen once the oil got good and hot and it seemed to be linked to left turns.
Friday at CMP I got to see the behavior in detail. I have an oil pressure gauge at the galley and at the Accusump. There is also a senser at the pump that is connected to the data logger.
I could see the 1.5 qt Accusump empty most of it’s oil in order to keep the galley OP up at CMP turn 1. Galley OP would drop to about 20psi. The Accusump then refill some, but then turn 3 would empty it completely. But just as it emptied, oil from the pump got to the galley so the OP just barely managed to stay up.
But then turn 4 would kick the sump’s butt and it would be dry and the oil pump seemed to want to take forever to get oil back thru the system.
Our oil pump doesn’t pump much volume. It’s not much more then a fast dribble. I think that that combo of no scraper and too much plumbing and crap that needed to be “charged” each time the system went dry, resulted in serious oil starvation.
Saturday morning I ripped out the whole oiling system and threaded the oil filter directly on the block like an E motor. I wanted to see what would happen. If you can generate the problem then you know that you are on the right track for understanding it. I saw oil pressure drop on left turns, but I also saw the oil pressure restored very rapidly. With the oil filter on the block and no oil cooler, once the oil pump starts pushing oil again, the galley seems to get the oil immed.
So if I was going to do all this oiling crap again, here’s what I’d do. Leave the oil filter in the OEM place and rig up some kind of sandwich adapter for the oil cooler. The sandwich adapter can also terminate the Accusump, but figure out how to put the sump closer to the motor.
Connect the sump with -8 hose intead of -10. That will reduce the oil volume in the plumbing.
Gotta have a scraper.
