This topic brings to mind a problem I encountered about 20 years ago on a 1690 Case (David Brown) 6 cyl. diesel. Farmer brought it in for a rebuild. It's an un-sleeved engine, so I ordered 6 new pistons from Case, and took the block to the machine shop to be bored out so they could press in liners. Mfr. recommended .005 piston to wall clearance, so we went with that. Put the tractor on the dyno and within 5-7 minutes it ran tight and stopped. Disassembled and found 6 scored pistons. Re-did everything, and got 6 new pistons, and the same thing happened again. Machinist and I were pulling our hair out. We called David Brown in England, and they told us "Yes, we know there is a problem when rebuilding those motors, but we can't pinpoint it." We ordered 6 new pistons, and while I was checking them with the micrometer, I picked up one of the previous pistons and discovered that it was .005 larger than the brand new one. Turned out that the odd alloy that David Brown was using for their replacement pistons, caused the pistons to "grow" .005 and "set" at that dimension. The cure was simple. We set the wall clearance at .010 and put her on the dyno. The engine sounded real scary for about 4-5 minutes, and then slowly it quieted down and ran fine. The machinist told me last month that he's done 9 engines like that since, with no problems
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Today's Featured Article - Pitfalls of Tractor Engine Rebuilds - by Chris Pratt. The first pop after you have put the machine together with your own hands is exciting and pleasing. The whole experience can be marred if one moves too fast and makes too many assumptions that they can just use "as is" some parts they should be closely scrutinizing and possibly attended to. In such cases, rework makes what could have been a fun project turn into an irritant or even a nightmare. Minor Irritants To give you an example of an minor but irritating proble
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