High Volume Oil Pump
 

Is it a good or bad idea to use a high volume oil pump to replace a standard pump in a absolutely stock engine? The application is a 502 Magnum MPI.

Re: High Volume Oil Pump
 

I WOULD NOT USE A HIGH VOLUME PUMP UNLESS YOU HAVE A LARGER OIL PAN.

Re: High Volume Oil Pump
 

I would save the money and run a stock one on a stock motor

Re: High Volume Oil Pump
 

I would recommend using stock volume pump and shimming the spring .125"

Re: High Volume Oil Pump
 

There should be no reason to go beyond the stock pump on that motor. Are you having an oil pressure issue?

Re: High Volume Oil Pump
 

That stock pump is plenty.

If you are going for more hp you should be concerned about the external oiling system ie:the stock merc oil fittings, lines - size and design.

Take a look at this good thread from Arcticfriends:

http://www.offshoreonly.com/forums/s...ight=oil+lines

Re: High Volume Oil Pump
 

I would do what Chris says if you know what he's talking about? He has a lot of knowledge with Steff's oil pans.

Re: High Volume Oil Pump
 

I don't but my customer base does. This shimming comes from some of the respected marine engine builders that we deal with on a regular basis.

Re: High Volume Oil Pump
 

One of the biggest problems with the Mercruiser oil system is that the oil lines they use are very small. They work okay with stock power, but if you start to modify the engine, you have issues with oil flow.

Shimming the oil pump will get you more pressure, but with stock lines, your volume will not increase, which won't do you a lot of good. If you shim it, AND use larger lines, then you will be on the right track.

Think of it as putting your finger on a water hose. You are still getting the same amount of water, its just coming out harder, because you did not increase the volume

Re: High Volume Oil Pump
 

The oiling system is a little different then yourhose/finger example.

The 'finger' is your bearing clearances and other orifices ie: things that will bleed off psi.

Say a pump has no psi regulator for a second.

If your engine needs 75psi for correct protection and your system actually gets to 100psi this means the pump has more volume output then the engine requires. Enter the reason for the psi spring regulator. If this is set for 75psi, in the above engine, then it will open at 75psi to bleed the extra volume of oil away from system to maintain this 75psi.

If you have a 75psi spring bypass setting, but your engine only produces 50psi of oil psi your pump does not create enough volume to reach this point.

So, if you have a 50psi spring setting and your engine maintains this 50psi, then your pump has enough volume.

If you take the same engine and pump but shim (or replace) the spring to 75psi and the engine reaches and maintains this 75psi, then the pump has creates enough volume to keep up - the system is using more oil volume. If it doesn't reach / maintain the 75psi, the pump doesn't have enough volume and a larger volume pump must be installed.

Sorry for rambling - hard to type vs talk .

Re: High Volume Oil Pump
 

Agreed. Just trying to show the difference between pressure and volume. As you said, its sometimes hard to type it the way that you want to explain it.

Re: High Volume Oil Pump
 

Yes, I am having an oil pressure problem in one motor. Somtimes pressure is normal, and then at times it drops down to as low as 10 psi (not after a hard run), I could just be idling at the dock. Shut the engine off and start it again, oil pressure may go back to normal (40psi at idle), or may me 10psi or something in between. Engine runs fine - I am pretty certain that the pressure relief valve in the oil pump has a problem. After this season, I am going to have to pull the engine an check everything out - was just wondering if it would be prudent to replace pump with a high volume style.

Re: High Volume Oil Pump
 

If the drop isn't related to temp, I'd look at the pressure sender/guage before anything else.

Re: High Volume Oil Pump
 

Hook a mechanical gauge and check it that way before you spend the time and money to pull the engine.

Re: High Volume Oil Pump
 

Sorry, I should have said that I have checked it with a mechanical gauge and the electric gauge operating together. Both read the same (high and low).

Re: High Volume Oil Pump
 

Just my 02 but make sure you check the pick up tube to the pump for leakage. This will - can cause problems. Also check pick up distance to the bottom of the pan.

For me with a stock 502 with proper bearing clearances a stock oil pump is the better choice. You really do not need 50psi at idle.

People seem to forget that a big oil pump relieving pressure just creates more heat in the oil.

Re: High Volume Oil Pump
 

As a general rule the system should maintain at least 10psi for every 1000 rpm. Preferably a minimum 30psi (warm) @ idle on solid roller and solid flat tappet camshafts to alleviate any valvetrain lubrication issues which can present themselves when running the higher valvespring pressures associated with the aforementioned applications.