How can you have one without the other? When I installed my Melling High Volume pump with my Canton pan the directions suggested I change the spring and run the softer one. What's the reasoning? The reason I'm asking is that when I start my car I get 40to 45 psi. When warm its about 25-30. But when I stomp it, it never goes much above half way. Is it supposed to be like that with a aftermarket pan?

 

This may provide some clarification for you-
http://web.camaross.com/forums/showt...threadid=69291

 

They are mutually exclusive. To get high volume the pressure is lower. To get high pressure the volume is lower. Think of putting your finger over the end of a running hose. As you restrict the flow, the water squirts out harder but less is coming out.

Unless you're running consistant high RPM's a high volume pump is not a good idea since it puts more oil up top in the engine and heats it up. The standard volume pumps do a more than adequate job in providing oil flow for most situations.

 

A high volume pump is bigger than a standard pump. A high pressure setup replaces the relief spring with a stiffer one, increasing the pressure at which bypass starts to occur. The pump is the same, just the spring is different. I am not quite one of the "big dogs", but my combo is close and I use a stock pump with a stiffer spring. Up until last year, when I set up with slightly larger bearing clearances, I ran a completely stock pump.

A pump, no matter how big, will not make any more pressure than the relief spring allows. If a pump is too small for the application it will not make enough pressure no matter how stiff the spring is.

Why replace something that works? A stock pump is fine.

Rich Krause

 

Listen to Rich ^^^

 

No. And that's not a good analogy when refering to an oil pump, which can be treated essentially as a positive displacement pump. The pump flow is controlled only by engine RPM. The pressure in the system is controlled by the resistance in the flow system, and ultimately by the relief spring pressure in the pump outlet. As Rich points out, a high pressure pump is simply a "stock" pump with a revised relief spring pressure. A high volume pump is a larger internal displacement pump, usually arrived at by making the rotors "taller".

 

I had a high volume/high pressure pump in my 77 Z28. On a cold morning I had like 100 psi of oil pressure and about 60 psi when everything was hot. All it ever did was suck the pan dry and make oil leaks really easy to find.