When I had the "brain" issue and was trying to find out why I didn't have oil pressure, I actually swapped out the oil pump for one i had on the shelf. It was an early, aluminum, narrow rotor pump and had about 50# at WOT and 20-25# hot at idle. But I had the original pump that was mated to the cam in the truck; so yesterday I unbolted the RH motor mount and jacked the engine up a smidge. I removed the aluminum pump and installed the newer wider rotor pump that went with the camshaft. Fired everything up and took it for a ride. Allowed temp to get up to about 200 degrees so I know everything was hot. Checked my pressures and had about 52# at WOT. But my idle pressure was up at about 35#. I am guessing the wider rotor pushes a little more volume at idle than the aluminum pump did. Now to find that pesky rattle I hear every once in a while!

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

That is as it should be. Look at it this way. If the rotor is 10 % wider, then at any given rpm the pump will pump 10% more oil. So with the restriction of the oil system being the same, the pressure will increase at any given rpm. This will hold true until the pressure reaches the pump bypass valve setting, at which point the valve will open and bypass the excess oil volume to maintain the pressure at that number.
This is why changing the bypass spring will have no effect on the low rpm oil pressure, with a given pump. The pump does have enough volume and just cannot supply enough oil to the engine. It is also why in most cases a slant does not need a "high volume" oil pump.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Charlie explained it very nicely!
Lou

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