question for the diesel mechanics

Posted the whole problem in Oliver and Cockshutt forum. Please go that forum as post is long due to all issues. Thank you.

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Have cockshutt 50 diesel standard bore. Replacement pistons are close to impossible to buy. One fellow has 60 over manufactured from another engine but not having oil ring below wrist pin and most likely not close in weight. The Cockshutt piston is two oil rings.This remanfactured piston is from a gasoline engine requiring a deep valve relief most not likely as strong and would require boring one cylinder too be bigger. As one can see balance problems are possible but not likely with the slower rpms. My thinking is thus my original piston is solid except for a small area of the top ring land broken out near the machined valve relief. Why not just leave the top compression ring out. Not a working tractor . Yes starting due to much lower compression is comprised, however it's only on one piston. I can get a 30 over piston from Phil H. He has only one.The cost is not so much an issue as availability. My one son who is a mechanical engineer can turn the piston down, however due to issues of re chucking an skirt flex it's not as simple as one would think.

I don't like taking any shortcuts on diesels!

But you gotta do what you gotta do...

My first choice would be to go with the .030 piston, bore that one cylinder. Running with one oversize cylinder will never be noticed.

I would not try turning the piston down.

Is the broken piston aluminum? If so, that would be my second choice. It could be welded. Build up the broken area, fill the entire top land with weld, turn a new ring land.

OK at the piston plant I worked at for ten years we would use a machine that had a ring of steel made that the skirt of the piston fit on real snug and would use a drawbar and a pin through the wrist pin hole to pull it tight on the ring. This machine would cut a profile on the lands and create what ever shape on the skirt, Barrel, half barrel taper etc.It was a Takesawa Cam turn. The tooling could go in and out as well as travel along the other axis of the part. Also pistons are not necessarily round and with a straight profile on the lands or the skirt. We had the blueprints for each part. OEM and aftermarket would be slightly different due to patent laws. Made a lot of parts for AC, Minneapolis, IH,JD, CAT, Cummins and others both OEM and aftermarket. The ring was a lot like a puck used to pull sleeves out, smaller than the O.D. but yet big enough to have very little free play on the inside. It had a step cut into it, and would be indicated in so they repeated dimensions.You can create a ring with some way to pull the piston into it,clamp the part and then chuck it into the lathe you could do it but it would take a lot of time.

Where did you work? A.E. Gertz, Lake City, Mn.?

Not sure if it was this forum or another one, but a guy had what I remember to be a 9 or 1030 Case. Was in very frugal mode engine needed a piston replaced. He had used spare parts out of another engine all the same dimensions except for the bore was an 1/8" different. (If memory serves me right) Put it together with two pistons a different size said you couldn't notice it one bit. I think he placed them half way apart in the firing order or one TDC the other BDC if that is possible in a six cylinder. Of course having the two may have been the reason for better balance. I agree on a slower tractor engine you would most likely not have a balance issue with one piston 0.030 over.

Extreme Tractor parts and Murphys have cnc mills and can whittle a custom piston pronto for only a few bucks.

the thing is ... when an oversize piston is made it is the same wieght as the standard bore piston for that engine.
but a piston out of another engine made to fit dont mean it has the same weight, as it should be weighed.
myself i would use the 2 larger pistons as running mates if i had to do that.