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Old 03-06-2013, 12:38 PM
BogiesAnnex1 BogiesAnnex1 is offline
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Originally Posted by daveh View Post
Hey guys,

I'm looking to replace my oil pump in my slightly modified 1971 Challenger 340with one of these since I recently bought a higher capicity oil pan. Any pros or cons are greatly appreciated.

Mopar Performance High Performance Oil Pumps P4286589 -

Melling High-Volume Oil Pumps M-72HV -

Sealed Power High-Volume Oil Pumps Z2244166V -

Depends, have more capacity in the pan doesn't mean you need a higher volume pump. It's good to have the extra capaicty but what's really needed is oil management in the pan. By that I mean trap doors to keep the oil around the pickup, and a windage tray and stripper to peel the goo from the crankshaft. High volume pumps really require attention to the details of oil windage as the extra volume of oil passing through the bearings as well as top end drainback can easily overwhelm the piston's oil control rings, this especially can get to be a problem with loosely fitted pistons, high silicon with close clearance to the cylinder walls are less of a problem, but old fashion cast pistons or those forgings from 2618 alloy can really result in an oil burner that won't quit as both like and need a loose skirt clearnace which lets the piston thus the ring package rock in the bore making it hard for the rings to seal up.

I'm not too crazy for high volume standard pressure pumps unless the bearing clearances are on the loose side. That lets the oil flow through the bearing quickly so that extra volume from the pump actually circulates. When the bearing clearances are production standard, especially if on the tight side, the extra oil flow from a high volume pump can't get out of the clearance fast enough. That creates a back pressure on the pump which when combined with a standard pressure relief valve ends up with the valve open most all time which is just wasted effort that heats and foams the oil while putting extra mechanicial loading on the entire cam drive system (read that power extraction as well as part wear) to drive the pump. The small block Chrysler when raced does show some oil system inadaquacies but these are not simply sensitve to volume and pressure increases for a solution. For a street engine, including a performance street engine, oil system changes to this engine are not necessary.

In the condition of a high volume with high pressure pump it is likely that the relief valve is not open so much of the time when the high volume backs up against close bearing clearances, but the wear and power extration figures remain on the cam and oil pump drive systems.

Whatever your decision on the pump, carefully disassemble the selected pump and inspect it for all the fits and clearances. We see enough problems with pumps to warrant this extra attention, it is way easier to fix errors and left in machining shavings before the engine is either fired up or heaven forbid fired up after installtion then to discover problems within the pump.

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