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Which Oil Pump

2K views 9 replies 6 participants last post by  ap72 
#1 ·
#4 ·
My 318 is 30 over. Has the 340 adjustable rockers and 340 cam. 051 heads 1.88/1.60 valves. The valiant it was in had 3.31 gears. Edelbrock 600 on streemaster 318 0-5000rpm single plane. If your setup is like this the melling standard output is fine.

Make sure the pickup is clearanced to the pan floor.
 
#6 ·
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.

Bogie
 
#8 ·
high volume pumps are for low rpm protection, not high RPM.

Once the bypass opens the high volume will flow no more than a standard pump- BUT below it (lower RPM) you will have more flow and pressure. I like them for street cars especially ones that have shallow gears (low rpm most of the time).

High volume pumps work well at lower rpm, but at higher rpm the standard pump actually works better- where the crossover is depends on clearances, oil viscosity, temp, and your relief spring pressure.
 
#9 ·
Hey guys I'd like to make a decision today so I can order the pump. I've got it narrowed down to either the high volume Melling or the standard Melling pump.

Melling High-Volume Oil Pumps M-72HV - SummitRacing.com

Melling Oil Pumps M-72 - SummitRacing.com

I'm leaning towards the standard because my engine really isn't that radical. The only reason I was asking about the HV pump is because of the deeper pan that I'm installing.

Any further suggestions will be greatly appreciated. Thanks

Dave
 
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