Alright guys, we finally got a straight answer back from the engineers at GM on what exactly the difference is in these pumps!

We'll start off with the 12586665 OE pump that started in the GenIII motors and carried over into some GenIV. This is not the high flow pump. This pump has a thinner gear set and smaller diameter compared to the high flow pump. Also, this pressure relief valve cracks open at 32 psi.

Next the 12571885 pump. This oil pump began its life in 2005 on the W-body V8’s and the LH6 5.3L in the truck applications of the Trailblazer/SSR's. This is the high flow oil pump, but no longer in production. This was in production until July, 2006. This pump is very similar to the 12586665 pump, but has a thicker gerotor with larger OD and a stiffer relief valve spring that cracks open at 52 psi. There are some differences also in the pump housing but nothing major. It was replaced by the pump listed below, 12612289.

Finally, the 12612289. As stated above, this pump is the current high flow pump in production. It is identical to the 12571885 pump, but the relief valve isn't as stiff. This relief valve cracks open at 42 psi.

We spoke with the GM engineering team and they informed us that these high flow pumps should not be run on the LS2/3 engines with the stock pan, because they were starving the pan of oil. At first it may not make sense, but what was happening is the high flow pumps were pumping the oil out of the pan faster than it could return. So after a short period of time, the big pump had emptied the oil pan of oil. We were told the big pumps generally go on aluminum block applications with phaser and/or AFM (Active Fuel Management AKA: displacement on demand) hardware. The small pump goes on all iron block applications as well as the aluminum block applications without a phaser and/or AFM hardware.

In conclusion: These high-flow pumps are NOT for everybody. For those wanting to use them, it would be in your best interest to run an aftermarket oil cooler or remote mounted filter so that you have the extra oil capacity needed for this pump! Of course, Scoggin Dickey has options on both of those available for you as well! For the guys not looking for the added cost of such add-ons, we still offer our blueprinted and ported LS1 pumps for $149.95. They will give you the added oil pressure that most are looking for, without running the risk of sucking your pan dry.

 

Matt- I know you worked your *** off to get these answeres. I was following the post on LS1tech. Thats for all the work, you saved me a $100

 

Where do the Melling high volume pumps fit in this scenario for an LS2?

 

TeddyCA, you can mail me some of that $$ I saved you whenever you're ready. See our website for the address

BillardCue: Melling makes a hi volume and a hi pressure pump. The average Joe on the street will need the hi pressure pump.

 

Matt,

Thanks for the quick response but actually my question was - does the Melling high volume pump suck the oil pan dry like the GM high volume pump you mentioned in the first post?

I'm building an LS2 stroker and purchased the Melling high volume pump for it.

 

I have not taken apart the Melling hi volume to measure the gear inside. But if it has the larger gear like the "LS4" pumps and is on the same scale of volume that they are, yes...it could be an issue!

 

good info

 

Another example of "more" is not always "better".

 

Are you talking the Melling #10296??

I would like to know this info as well. I run the 10296 and see around 42psi at idle. When I get on it I see as high as 60psi.

 

Excelent information, thank you.

 

On older Vettes and small blocks, a higher capacity oil pan (5 or 6 quart) was a necessity for a modified engine. In addition, it was common practice to open up the oil return holes in the heads (holes almost always had a lot of casting flash that partially restricted the return hole), and paint the lifter gallery with glyptal or an oil resistant paint to speed oil return to the pan.

In lieu of a high volume pump, an alternative is to shim the pressure relief spring in the pump using a washer of suitable diameter about 0.10" thick or maybe even 1/8". This should take the crack open point from about 40 - 42 psi up to about 60 psi. A word of caution though - avoid shimming too much and if you're running higher viscosity "racing" oil and then buzzing the engine too high before oil has a chance to warm up. Pressures can go WAY up and extrude the filter gasket at high velocity with subsequent loss of oil. It makes sort of a "poink" noise. Don't ask.

Charlie

 

I'd be listening to this guy, sounds like he paid well for this knowledge.

I can also tell you exactly what pressure the motorcraft oil filters blow the can clear of the base.

 

Good stuff, Thanks for sharing

 

very good info
i autoX mine, and as the oil gets HOT the pressure drops
i wonder what pump i should replace my ported LS6 with?
the extra pressure should support an external oil cooler- safety benefits needed