Oil pressure drop thru 1/4 mile

Derek Wood wrote:

dfree383 wrote:have you tried running less oil, could be a windage problem.

My last motor had issues running capacity in the pan, when we dropped a quart and a half everything stablized. That was a 9 qt system, no accusump.

Tried from 15 to 18 which translates to 12 to 15 in the pan. Will update as we learn. Thanks for the input ,Derek

Whats the capacity of your pan?

Thier is no need in the world to have 12-15 Quarts in the pan.

Typical systems run fine with 8-9 or even less.

We have been running a 545 BBF in a dedicated drag car for the past season. Prior to this season it was 460. In both formats it would drop oil pressure to 0 when under brakes in the runoff area. Only for a second or so, but 0 nontheless. We are running a Moroso 10 quart pan with rear pickup, so the 0 reading is partly due to the rear pickup but with 10 quarts you would think there would still be oil around the pickup. Anyway, we will run an extra litre in the pan to see if that makes a difference, but when we check the motor the bearings look fine and all seems well. Looks like the engine can handle a brief 0 pressure situation when not under load.

If you are only dropping pressure but not going to zero under deceleration then maybe you shouldnt worry too much. Have a look at your main bearings to satisfy yourself that there is no issue. We pull the caps on our engine at the end of each season and go looking for problems no matter what - we use our down time to check for emerging issues.

Derek,
I like your idea that the dual pickups may be part of the problem. There should not be a need for dual pickups if it's a chassis pan. Uncovering one of the pickups would cause the pump to cavitate. Another thing to check is to make sure that the pickup has a gasket and is not drawing air between itself and the pump. I ran an Accusump on a 534" motor with a Moroso 10qt chassis pan. I would kick the car into neutral after passing through the lights and never saw the pressure drop.
Mike

We have similar brand setup for the pan (ours is flat), pump/pickup, accumulator and quantity of oil. We run 20-50 Brad Penn and a Jomar filter.

We have 50 PSI at "idle" the start of the run and 80 across the line. That's with header evac. We see about 1 PSI (about 2") vacuum across the line.

If you are running a vacuum pump could your relief valve be set too high?