Posted by Tom in Indiana [172.69.90.49] on Sunday, July 07, 2019 at 13:49:16 :
In Reply to: Re: Zero oil pressure at idle posted by Mark D. [172.68.65.39] on Sunday, July 07, 2019 at 09:22:34 :
The reason for the larger screen from the factory is many-fold. Less risk of cavitation from a rounded, larger surface area. More screen area= less chance of being stopped up by sludge and debris. But the main reason is because yes, the tube is 3/8", but the pickup screen sits a fraction on an inch from the oil pan floor, and since there may not be 3/8" of an inch of clearance between the bottom of the aftermarket pickup screen and the bottom of the oil pan, it may potentially have to pull oil from the sides to compensate for the inadequate amount available immediately below the pickup, which will cause cavitation, as well as lower oil pressure. With an HV oil pump, it will be exacerbated. If the pickup screen is also square/rectangular, it also decreases input flow, albeit by not a drastic amount. If it is a "gravity flow" pickup (shaped like a "J", and I have seen a couple of them), they can literally create a vortex within the reservoir of oil and pull air- instant zero oil pressure. A pin hole in the tube at any point above the pickup screen can also cause cavitation, no matter how small. Fancier isn't always better. ;)
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