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Rebuilding my oil pump for the 1951 288, and came up with a few little questions.

Does this dimple on the driven gear mean anything, should it be facing in or out from the pump? See picture with red arrow. My guess is that it is 'vollig wurst' totally sausage hehe.

Also, the pressure relief piston...it feels smooth, but looks a little rough. Here are some pictures. Should I try and make it look nicer with crocus cloth? -whatever crocus colth is...

I've never used crocus cloth, but can get some 1200 grit or finer something (not sandpaper) at a hardware store here I guess.

Thanks guys.

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Hello,

Crocus cloth is jeweler's Rouge polishing cloth.

Jerry

Here is a brief description of crocus cloth & uses.http://www.ehow.com/about_6622789_crocus-cloth-used-for_.html

The important thing is you do not want to use a final grit so aggressive or hard it leaves microscopic scratches on a finish. Most sandpapers with emery or aluminum oxide or similar, even though a very fine grit, are hard and will actually roughen a precision surface.

Regarding the piston, unless there is a sharp burr or other deformation on the surface, I'd leave it alone. If some spot does require attention, do the very least work necessary to allow the piece to slide freely in the bore.

I don't know the significance of the mark on the gear but doubt it has any significance to performance.

The pip mark on the gear tooth was probably put there by a former rebuilder so that the gears would re-index exactly as they came out. Is there a corresponding mark on the DRIVE gear????? If not then the mark would be aligned with the key way of the DRIVE gear.

However, it would not be good eng'ring to key a gear to the shaft with the key groove directly at the root of a gear tooth.

The mark probably has no significance unless one of the above conditions apply.

While the pump is apart. Mic the thickness of BOTH gears to see how close they are. I'm not sure what the spec should be on it but i would guess no more than 0.002" difference at the max.

If there is more than .004 difference then the gears were probabaly replaced with misc. gears at one time.

If the pressure relief piston is that rough then how bad is the bore in the pump body??????

MEasure the diameter of the piston and the length. I would try to find a new one or a find one from someother brand of pump that would fit. U can drill your two holes if needed. I doubt that it is too hard to drill with a common drill bit.

My biggest worry at this point would be with the bore that the piston slides into.

I went and looked at the eHow .com instructions for the use of crockus cloth. I didn't see any indstruction to use any kind of cutting oil. Double check with a machinist about using some very light machine gun, instrument oil or coal oil while polishing with the cloth.

Or let me put it this way:
I've polished out crankshaft jounals with crockus cloth that resembles a 1000 to 1200 grit emery cloth. I've NEVER used it without using coal oil or somekind of extremely lite lubricating oil.

Last job was a 2.0 F OHC hi reving engine. It's ran just fine now over 25k miles.

Double check with some of the old school German machinists there in Germany about this application for polishing with crockus cloth.

When finished polishing with the crocus cloth be sure that there is no sharp edge at the open end of the piston. Round it ever so slightly just to remove any sharp edge at that point.
Sharp edge could cause it to hang up under operation.

Agree with PV8 about the oil and checking the bore. If the valve moved freely before, then as O_D mentioned, probably not a major worry. I would just lightly clean any varnish or similar deposit off and verify no burrs and it slides smoothly.

Apologies for not paying attention to that eHow site not mentioning use of any oil. Most machinists and their supply sites do recommend the use of lapping oil or a good quality honing oil.http://www.goodson.com/store/template/product_detail.php?IID=396&SID=7952cf3e94dad5b91ce7f0e5eae0071b

For this use, I would think 3 in 1 would be fine but if polishing a shaft seal or bearing surface would go for the thinner or more refined good stuff.