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i've heard a number of people express a preference for the aluminum body schadeck pumps, over the cast iron melling pumps.

but i've also heard (sometimes the same) people say that aluminum full flow covers are junk, that the wear.

what gives? how can cast aluminum be good enough for the pump body, and billet aluminum not be good enough for the pump cover?

thinking of expansion coeffiencts: aluminum body + aluminum cover sounds good, particularly in an aluminum case. iron body + iron cover (ala berg) sounds pretty good too, but might not seal quite as well to even a mag case. but aluminum body + iron cover? seems like those two components are going fighting each other every time you run the engine.

can someone please explain this to me?

The iron cover works better as the endplay "maintainer", where as when an ally cover wears, the end play increases and thus the pressure isn't maintained. The cam drive tang imparts a bit of pressure against the cover. The oil grooves around the face of the pump body work sort of as a suction device feeding any oil leaking out past the inner part back into the suction side of the pump. When cover (steel, cast iron, or ally) is correctly sealed, as in the grooves not blocked with gasket sealer, I never see a leak out the cover/pump body interface.

The pump body to case seal is where a cast iron pump is at its worst. A full flowed cover and an o'ring seal on the pump body reduces the expansion caused problems. Without, the pump can suck air on the inlet side and/or leak pressure out before the reliefs. A cast iron pump is at its best at eating crude when compared to an ally pump. But that doesn't fix the problem of where the crude came from.

I prefer ally pumps and steel covers, just like the metallurgy VW originally used.

thanks very much for the clarification!!!

Tom Notch wrote: The cam drive tang imparts a bit of pressure against the cover.

is this true even with straight cut cam gears?

Tom Notch wrote: A cast iron pump is at its best at eating crude when compared to an ally pump. But that doesn't fix the problem of where the crude came from.

did you mean crude, as in a oil - or crud, as in gunk?

Tom Notch wrote:I prefer ally pumps and steel covers, just like the metallurgy VW originally used.

who makes a good steel full flow cover?

gcorrado wrote:thanks very much for the clarification!!!

You're welcome

gcorrado wrote:is this true even with straight cut cam gears?

Yes, straight cuts do nothing to affect the pump drive.

gcorrado wrote:did you mean crude, as in a oil - or crud, as in gunk?

Crud, as in Foriegn Object Damage

gcorrado wrote:who makes a good steel full flow cover?

I use Berg covers

great info.

Tom Notch wrote:

gcorrado wrote:who makes a good steel full flow cover?

I use Berg covers

okay, thanks. i'd thought the berg covers were all iron.

I didn't claim they were steel, I just said I use them. I do not know of a steel full flow.

speaking of such.
I have just installed an anodised aluminum pumpcover from a known vendor/manufacturer, on a hefty engine. At the end of the season we will take it apart again and see how it holds up. - The claim is that since its anodised, it will not wear, or at least very slow. - Time will tell.
T

one huge problem is pumps and covers are NOT FLAT. If you put one on a belt sander you'd be shocked! Some take a LOT of surfacing to make them flat. If they are not flat, that's a pressure leakage, especially at idle!

John
Aircooled.Net Inc.

A belt sander, John? That may be good for getting a really bad pump better, but the ideal is to lay a sheet of 120 grit sandpaper on a flat piece of glass like is found on any side Beetle window. The results of that will surprise you.

I was simply making a point. Covers are NOT FLAT out of the box.

belt sanders, glass and sandpaper, both work.


John
Aircooled.Net Inc.

farmer wrote:speaking of such.
I have just installed an anodised aluminum pumpcover from a known vendor/manufacturer, on a hefty engine. At the end of the season we will take it apart again and see how it holds up. - The claim is that since its anodised, it will not wear, or at least very slow. - Time will tell.
T

Thick/HARD anodization (looks dark grey>black usually) should hold up well.
(Berg sells Schadeck pumps fully hard anodized and o-ringed)

Takes a licking from Scotchbrite (cleaning) and high power Plasma+Fluorine/Chlorine where I work every day without a whimper.

(Reminds /me to get my pump cover (or maybe the whole thing) hard anodized...~$50)

The pretty color stuff is generally... Bling.

BTW, is anyone selling Melling pumps with an o-ring yet? I'd buy one like that...

I have been trying to figure out how to do mine just in case, looks like you'd have to make a pump body holder to chuck up in the lathe.
Once someone had that made it could be done in a few seconds.

As to flat, 400 wet or dry on a 1" thick slab of optical flat is my method on the body/gears and cover.

Works well on PC processor heatsinks too.
(They usually are never ever even remotely CLOSE to flat, even if they come highly polished)

While I was stumbling around using Google tonight trying to figure out what pump I should run in my "new" wasser, I found that EMPI of all people flog HD "billet" steel covers in both std and full flow versions, cheap of course. (please don't throw rocks for the suggestion... I KNOW it's EMPI)

Easy/cheap solution to the end play issue w/aluminum pump covers. (The hard anodized would be "trick" though)

(Being "modern" EMPI, I would DEFINITELY check it for flatness, and perhaps holes in the right place...)

I also think I have figured out how to cut that o-ring groove. Will post if it works...

I have o-ringed 3 Melling oil pumps (for my own use), one of which has literally 150+ passes on it and has worked out well.

It sounds like you might be machine-tool and vacuum system savy;
You hold the pump body in a 4-jaw chuck in the lathe, indicate it in to .0015" or better. I cut an o-ring groove on both sides of the inlet ports, but you could choose to cut only one. It's been a while and I didn't write down the part number, but I got them from Parker who these days must have an on-line catalog with engineering specs (you've likely seen the Parker oring book, they always had a real good hard copy catalog that includes groove dimensions with tolerances). Going from memory, I think I used 3/32" cross section o-rings.

The only down-side is you can't instal the pump without splitting the case. It tears up the o-rings as you push the pump body in

Tom Simon wrote:I have o-ringed 3 Melling oil pumps (for my own use), one of which has literally 150+ passes on it and has worked out well.

On that topic Berg's pumps come cut for the O-ring.

Good to know it's no big deal to cut one for it myself.

gcorrado wrote:

Tom Simon wrote:I have o-ringed 3 Melling oil pumps (for my own use), one of which has literally 150+ passes on it and has worked out well.

On that topic Berg's pumps come cut for the O-ring.

Good to know it's no big deal to cut one for it myself.

It's no big deal if you happen to have access to a ~4" or larger LATHE.

I made a "truing" jig to get things pretty close, goes in the drill center, bit of 1" trued up stock with an old stock cover bolted to it. Makes it quite square.

Works great, I dual o-ringed the CB drysump pump,, and single ringed the 30mm Schadeck.

The Melling will get the dual o-rings, so the thermal cycling size changes don't shred the paper seal to the block. The block-to-case seal will be the o-rings.

(Will post pics)

I'm thinking about doing the "pressure balance" grooves in the Melling ala Canton, as the iron pump and steel gears will stay in tight tolerances at temp, a little LESS pressure will almost certaily be a feature.

(Note to self: post pics)

The o-rings shouldn't get torn up IF you deburr/polish/relieve the opening and related ports, and grease it up a hair.

O-rings like very smooth surfaces. O-rings die on sharp edges...

I want to say the o-rings I used were a ~2-136 or 2-137v75...

The cases(or pumps) I have on hand are so loose...