Doppelganger

Hi all, ive got a 1999 4bm 880 vortec engine coming which was in a truck. I'm gonna rebuild it and use my CFI setup with bored out TB's and a Renegade manifold. I was looking at parts and the HV oil pump I was looking said it was for earlier years. Is there a difference for later ones or just the distributorless engines? As im using my original distributor will an early pump still fit the later block? Its a roller cam block but for now i'll be using a flat tappet cam from Comp cams.

Thanks in advance.

Rob

sofakingdom

iTrader: (1)

Don't use a HV pump. If the motor has stock bearing clearances (.0015" - .002" kind of range) it doesn't need it and won't benefit from it.

Use the M55A pump, IS-55E (make sure it's the E) drive rod, and whatever pickup fits your pan. Which I think just the regular 55S fits most of them but be sure before buttoning up the motor. You could also make your own M55A by using a regular M55 and the Mr Gasket spring, but then you'd have to do a slight amount of work.

The distributorless engines use a partial distributor to drive the pump... basically, imagine cutting a normal one off to where it fits under the intake. The pump itself is the same. Pretty sure the drive rod is the same.

Doppelganger

Great stuff thank you. Sorry meant HP not HV.

Thanks again.

sofakingdom

iTrader: (1)

Right: the M55A is the high-pressure normal-volume one; comes with a relief spring that gives around 45 - 50 psi at cruise. The Mr G spring usually seems to give slightly higher pressure than that but not greatly different. The 2 approaches are pretty much equivalent.

The E drive rod has a metal collar as opposed to the normal plastic POS.



Another approach we used to take sometimes was to use a normal M77, for big block. It has the advantage of having more teeth on the gears, which results in a smoother load on the distributor and therefore less "spark scatter". This requires some finagling with the pickup though: the SBC pickups are too long. Not really for the faint of heart.

GeneralDisorder

iTrader: (1)

Melling makes the "Shark Tooth" pumps that eliminate the pressure pulses like a BB pump (but better) and are direct fit like the M55A. They also come with the chromoly pump drive included. Standard volume, high pressure are part numbers 10553ST (for 5/8 pickup), or 10554ST (for 3/4 pickup).

Stock Vortec pickup is 3/4"

GD

Doppelganger

Thanks guys, how does this one look?
Look at this on eBay http://www.ebay.com/itm/264297894766

Thanks.

sofakingdom

iTrader: (1)

Might not be the right pickup. There are several: S, S1, S2, etc. Other than that, looks OK to me. You can get the other screens at AZ if that one isn't right.

Or, check out those others that GD posted about... I wasn't aware of those.

Don't make too much of a priority out of the price. After all, we are talking about your OIL PUMP here. Get what works the best in your situation. Pay what it takes, but don't waste money on stuff that doesn't do you any good.

NoEmissions84TA

iTrader: (1)

The Melling 10552 has a 10% increase in volume, but also the shafts of the gears extend into the cover for added support, and the cover is doweled to keep it from moving.
https://www.melling.com/product/gm-c...t-performance/



Whatever one you choose, be sure it does not have the weak mounting base (left). Those are known to break off.

NoEmissions84TA

iTrader: (1)

Here is that picture comparing the two:

Doppelganger

Thank you for all of the excellent information Gentlemen. I think i'm going to go the shark tooth route as this seems to be a nice upgrade over standard.

NoEmissions84TA

iTrader: (1)

Be aware that a lot of people that have used the SHARK TOOTH pumps have complained about gear noise. Do a search - you'll find it.