So general consensus is get a stock replacement Melling pump with the white oil pump spring if you're car is basically a daily driver with occasional visits to the track?

-B

 

Makes sense to me.

Rich

 

That's what I have and it is great!

 

I've seen several comments about how a high volume oil pump can suck the sump dry and cause an excessive amount of oil to accumulate in lifter valley due to inadequate drain back to the sump. I just can't understand how this can occur.

Please bear with me as I do a brief review of my understanding of the SB Chevy lubrication system. The SB chevy lube system has the oil pump pumping oil thru the filter to the main oil gallery, and simultaneously to the left and right valve lifter oil galleries. The main oil gallery supplies oil to the camshaft bearings, then ported thru the block to the crankshaft main bearings and then through holes in the crank journals to the rod bearings. The oil that leaks past the bearings is slung out, as the crank rotates, on to the cylinder walls, pistons and piston pins and then drains back to the sump.

The oil that is directed to the lifter galleries pressurizes the lifters, is pumped through the lifters to the pushrods, through the pushrods and finally, what leaks out between the top of the pushrod and the rocker arm cup is splashed around to lubricate the rocker arm pivots and valve stems. The oil that leaked past the rocker arm cup drains back to the sump though drain holes in the lifter valley. The timing chain, sprockets and water pump drive are lubricated by oil that leaks past the front cam bearing, by drain back oil from the pushrods, and from the 0.20" drilled holes in the plugs that are in the front lifter oil galleries.

The oil pump is a positive displacement pump, with a spring loaded bypass (pressure relief valve). The pump will only pump the amount of oil that is required to fill the voids in the oil galleries, the bearing clearances, the lifters and the pushrods. Excess oil is merely bypassed by the pressure relief valve to the pump suction.

So how is the pump sucking the pan dry and filling up the lifter valley with oil?
If the sump is being sucked dry, the pump has to be pumping it somewhere else, other than the components that I described above.

Chris

 

My thoughts exactly, I can understand a high volume pump wasting power by bypassing excess pumped oil but unless there is another problem that is causing excess bleed off (worn bearings) how do you run a sump dry.

BTW isn't the stock lt1 pump a high pressure upgrade over previous chevrolet sb pumps.

John

 

I guess there's always room for another opinion huh?

I'd use a std volume pump in an engine with the stock pan, std clearances and no drainback improvements. Works fine for lightly modified stock stroke engines.

For any halfway serious stroker or near stock displacement revver, I have and will continue to use an HV pump. I don't do so without a good pan and drainback improvements. I don't use tight mesh screens either.

When I drag raced and used external oil pumps, we always played with pulley ratios. That's why it surprises me when the consensus here believes that the HV is what costs you all the hp. My findings were that too much PRESSURE is what cost the most HP when the revs got going. Talk to some racers and see what their findings are when slowing the pumps down.

More volume = more pressure. Pressure is simply a resistance to flow. You can't exclude one from the other. In my opinion the real issue with an engine that can build RPM in a hurry is getting the oil to the bearing before the loads are seen. That and getting enough oil through there to cool things off.

Everyone sees it differently but I haven't had a bearing problem in a wetsump for probably 15 years. Have seen plenty of guys springing stock volume pumps for their race cars with problems though. Who knows... it's always a tough call but I do know what works for me.

-Mindgame

 

Thats actually what I meant if you are bypassing a high volume pump pressures are higher than they would be with a standard pump that is operating at a lower pressure.

I have two lt1's a 383 (600 + RWHP) and a 396, both have high volume higher pressure pumps. The 383 has seen 3 years of torture and still runs almost the same as when it was new.

John

 

That's the point I was driving at. The only oil that's going to get to the top end of the motor is what is forced through the hollow pushrods. High volume or standard oil pump, the only thing that will change the volume of oil through the pushrods, once the system is fully pressurized is the actual oil pressure that the pump produces; and that is governed by the relief valve spring. As far as I can determine, the high volume oil pump will prime the system quicker, say after shutdown. But once the system is primed, the volume of oil flowing through the system is determined by (1) the speed of the pump and (2) the rating of the pressure relief valve spring. The high volume oil pump can't suck the pan dry because there's no place for the pump output to go.

The downside to the high volume oil pump would be (1) more power required to spin it and (2) more heat build up in the oil due to the pump recirculating the excess pump discharge through the bypass (i.e., relief valve).

Chris

 

I agree w/ Mindgame...been running HV oil pump with the pickup 3/8" off the bottom of pan(canton 7qrt) for over 4yrs with no issues. My engine builder recommended the HV pump also. I see 70psi at cold start idle, falling to 30-40 when warm..50-60 at WOT when warm in the upper rpms..

Cody

 

I think one thing that can be said is if you're going with a high volume oil pump, upgrade the oil pan too. It's cheap insurance and you get better oil control. Whether you go with a high volume or "high pressure" would depend on you're engine builder and some other variables. Everybody has their own opinion on what works better but if you get the correct supporting components, shouldn't be a problem.