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Discussion Starter #1
I have an aluminum moroso 20485 oil pan. It has spots about 1/2 way front to back for drain backs but seems like the g-force would stop the oil from draining forward to the ports. I installed drain backs to this spot and didn't help. There is another port about 3" up from the bottom of the pan that is clear at the back. It is in the oil when not running. I pulled the plug and 1.5 qt came out. My question is will the vac pump want to pull the oil up the drain back hose if it has oil covering the lower end of the hose? It pulls around 15" of vacuum. It looses all oil pressure on decel so I just shut it off but would like to be able to fix it if possible.
 

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The quicker you go, the worse the oil pressure issue will become on deceleration with a wet sump. The aluminum block is also a likely contributor of the issue because of how the lifter valley is built with the ribs and drainback doesn’t seem to be as good.

As for drain-back locations, I don’t have hands on experience but I would think placing the drain back in the lower port would not be very conducive to flow.
 

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Discussion Starter #4
Put it in valve over. Not pan. Of fuel pump plate might not be readout rite.
The vac pump is hooked to the valve cover, drain back lines go from back of the heads to the pan. Just wondering if it would try to pull oil up the drain backs. I say no but buddy says worth thinking about.
 

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Discussion Starter #5
The quicker you go, the worse the oil pressure issue will become on deceleration with a wet sump. The aluminum block is also a likely contributor of the issue because of how the lifter valley is built with the ribs and drainback doesn’t seem to be as good.

As for drain-back locations, I don’t have hands on experience but I would think placing the drain back in the lower port would not be very conducive to flow.
Do you run an accumulator or just shut it down?
 

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My vac pump is plumbed into the valve cover. Regulator is on the pump. Oil drainbacks at back of heads to bungs on the pan welded in locations next to main webbing...never an issue with drainback. Aluminum block as well....
 

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We run a dry sump on the TS truck so I don’t have these issues. In my 5.2x roadster, a dry sump won’t fit and I have an accumulator. i started with a moroso box pan and it lost pressure on decel. Switched to a stepped Williams pan and still lost pressure on decel.
 
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