MV-55 i believe.

 

Is it 3/4 or 5/8?

 

That will depend on your pick up diameter, I think after 95 GM went with the 3/4 inlet. I will tell you the 3/4 inlet pump is more than twice the cost of the 5/8.


And a high volume pump will suck a stock pan dry, ask me how I know. In 2nd gear at 4000 rpms at WOT, the engine would loose ALL oil pressure. If you rolled into it slow it would fluxuate badly but not drop to zero. At WOT it would disapear. There's a lot of things out there that people say are true that aren't, but I will tell you this one is true, it could have cost me an engine.

 

The MV-55 is a 5/8"
The MV-155 is a 3/4"

Add an H in front for a high volume.

Since I see so many posts on this topic, I thought I would elaborate.... FYI.

Small Block Chevy motors need approx. 10# per 1000 RPM for long life. More is not generally necessary & often less pressure will make a few more HP. I can't find the tests I had on file, but I think it was under 10HP between the extreme upper & lower limits.

Too low & you may get to pick parts up off the ground. Some drag racers have run as low as 20# pressure & 3qts of oil to gain some power. Some people will do anything for that last hundredth of a second.

Keep in mind high pressure pump is basically a stock capacity pump with a (stiffer) higher pressure relief spring. It will not raise pressure unless the pumping capacity is sufficient to build greater than stock pressure. If your car only builds 25# at idle, the high pressure spring will do nothing for you. Stock relief is approx 45-50#. Keep in mind that a high quality pump will build more low RPM pressure than a cheap or worn out one. The Melling pumps come with a high pressure spring in a bag with the pump.

A high volume pump will likely increase pressure at low RPM & will increase to the limit of the relief spring. True, with a stock pan & poor baffling, it may suck the pan dry. With large bearing clearances & sufficient pan capacity, it will work fine, but may draw a few more HP. Most stock type engines do not need this pump.

A pressure balanced pump has an internal anti-cavitation slot to increase pumping efficiency at high RPM. This provides better pumping at high RPM, but will cause a loss of pressure at idle. This type is not a bad idea if you intend to frequently see 7000 or more RPM or run at sustained high revs. If you have an anti-cavitation high volume pump, idle pressure will still be good.

Best advice I can give is do not buy what you do not need, but also do not skimp with poor quality components to save a few $$.

Hope this helps.

 

I posted this in another thread. Pretty much mirrors what Lonnie said with a bit of additional info.

There is no reason not to use the stock pump and a major reason not to use a high volume pump. The high volume pump, at high rpm, can pump the oil to the top of the motor faster than it can drain back. If severe enough, this can starve the bottom end of oil leading to engine failure. A minor reason is that it takes more power to drive a larger pump. The stock oil pump is cheap, reliable, and delivers appropriate volume. A good aftermarket regular volume pump is a viable choice as well.

Oil pressure in small block and V6/90º Chevrolet engines is regulated by a spring in the oil pump cover. Spring PN 3848911 (color-coded white) produces approximately 70psi maximumoil pressure. With a stock spring the pressure will max out at about 50-55psi. Depending how high you want your oil pressure will determine which spring to use. FWIW, NASCAR engines are usually run at 50-60psi from what I hear. Not sure why you would need more, but some people just seem to like it! A high volume pump will not produce any greater maximum oil pressure - this is regulated by the bypass spring. In an engine set up with large tolerances, a stock volume pump may not produce enough pressure at idle or even at higher rpm. That is the only good reason to use a high volume pump. If a stock pump can't produce enough pressure, unless the motor was specifically set up "loose", the motor is on its' way out as the clearances have loosend up.

A good aftermarket replacement like the Melling is fine, just don't use a high volume pump.

Rich

 

so rskrause: Since I am purchasing the summit rebuild kit it comes with the high volume pump. I am very tempted to use this pump due to the fact that I am only going with a 355. However, from your explanation I should be using a stock type pump with the white spring. Should I just sell my high volume later or would you suggest using the one that comes with the kit?

 

I know this question wasn't directed at me but I will answer it. I used the summit rebuild kit for the 93Z that I did, I used the pump that came with kit. After it sucking the pan dry and possibly causing the engine to loose a bearing, I bought a stock pump and put it in. The oil pressure is the same as it was with the high volume pump except for one difference, it doesn't loose oil pressure at WOT.

 

Thanks! Did you go with the white spring as well or just stick with stock all the way?

 

stock

 

I am in the process of building a all forged 355 that will see around 420-450rwhp, and I am going to be using a milodon BBC converted to SBC oil pump.. I figure its cheap insurance.

Just my .02

 

Dangit!! I ordered the 3/4 instead of the 5/8!! What will I have to do to make it work?

 

Just a 3/4 pickup. Its not rocket science

 

You need to read this thread. It's "insurance" that you are risking a big problem for NO BENEFIT? USE A STOCK VOLUME OIL PUMP. An HV pump costs HP, risks major engine damage, and there is no up side to using a HV pump. I do use the white spring for a motor that will regularly see 7,000+rpm. For a street/stip motor, use the stock spring.

Rich

 

e=mc2?

 

The BBC pump is even higher flow than a SBC high vol pump by about 20%. Unless you have a serious pan, do not do this. Unless your bearing clearances are .003 or more, you do not need it.

I ran one of these in one of my cars before. It would blow the oil filter gasket if you revved it before it was at full operating temp. It used to wrap the gauge past 100# at idle on start-up. Definitely not for anything to be street driven in the cold.

I "thought" I needed it because I was turning 8K, but would not do it again.
Everyone is giving you advice for a reason.......