I gather from Abrams info that he's peering into the cylinder, looking at the top of the piston, and can see the top ring in the gap between the liner and piston.

This is not uncommon with older, high hour tractors. The top of the piston above the top ring land, wears a lot more than the rest of the piston, from the top ring down. This is caused by carbon buildup on the section of the liner above the top ring's highest travel point.
The skirt clearance is probably high, but still acceptable.

Mikes figures and info are good, for someone doing a full rebuild from scratch, and wanting a top-class, end result.
The difference between new, re-assembly clearances, and "operating clearances" after many thousands of hours, is considerable.

You can have a lot of piston-to-liner clearance, worn rings, and ring grooves .. and the engine will still run happily and work O.K.
It'll have noises .. from piston slap, wrist pin bushing wear, and ring clearance .. and use oil .. but it will start O.K. and run O.K., and probably smoke a bit.

If Abram just wants to fire up the old D2, it will probably run O.K., as-is. If the neighbour is prepared to spend a lot of $$ to invest in a heap of new parts, and overhaul the engine, Mikes figures are the ones to follow. I'd suspect the neighbour doesn't want to spend any more $$'s than necessary to get the D2 running again.

And probably won't have power enough to knock the fuzz off a dandelion.

HA! well i just want to drive it

LOL .. just as I thought! Was it running previously? Why did it stop? Has it been parked up, and is just stuck? I'd say she'll run O.K. if it was running when it was parked up .. provide that wasn't too many years ago ..

"OzDozer" wrote:

LOL .. just as I thought! Was it running previously? Why did it stop? Has it been parked up, and is just stuck? I'd say she'll run O.K. if it was running when it was parked up .. provide that wasn't too many years ago ..

my neighbor had it parked about 5 years ago because of accidently cracking the block (he forgot to add antifreeze and a cold night came around) the pony and main cracked, and he hired a welder to fix the block and pony. the welds looks good and i tested the main and pony block by bolting the heads on and pumping water through the blocks while opening the drains on the oil pan on the main and petcocks on the pony, and no water came out! so hopefully it will be ok when running. the governer, fuel injection pumps, and fuel pump are all removed from the tractor. so while i have them off i've been cleaning everything up.

i'll get some pics on thurs hopefully for you guys.

I agree, you will have some movement at the top of the piston due to the wear in the cylinder and the taper from the piston but it does sound like an entire sleeve assembly kit is in order.

If I remember right the pistons are machined a little smaller diameter above the top ring groove to the top of it.I have seen lots of them scored from the carbon above the top ring and is very common on them.

Cat have a name for the condition that pistons exhibit, where the top of the piston above the top ring is worn away - it's called "carbon cutting".
It is caused mostly by running engines too cold, or with excessive oil getting past the rings - both of which, create deep carbon buildup on the top part of the cylinder liner.

"Old wrote:

And probably won't have power enough to knock the fuzz off a dandelion.

Good point there OM... Even a worn out engine has its limits. Normally when an engine with 3.750 bore size has upwards of .010 at the skirt it is borderline for a rebuild. If a piston has too much slap it can fracture the pistons cause excessive smoke and rattle. If the man is going to work it and use it hard then it needs to have the power to do the job. On this particular engine, we do not know all of the facts. In most engines you can rock to top of the piston back and forth and to the layman it doesn't look good when you can see the rings on the piston while it is still installed. Soome pistons I have ground have .020 of clearance above the top land and more on the lower lands. The important fact is how much clearance you have on the skirt. You have to get all the specs and measurements to make a good judgement call.