The pictured engine is out of a L series Twenty in the late 400 serial number range.  I was going to use this tractor as the base for my Twenty restoration until I found major trani problems.  This engine currently has Twenty Eight jugs that have been rebored .060” over.  How many hours or how much dust has this engine eaten to go through its original set of jugs and then the Twenty Eight jugs with at least one rebore and then wear them out again? 

Hi, naylorbros.
An International Harvester trained mechanic told me back in 1970 that an egg cup full of dust going into a TD25C engine over 8 hours would be enough to render it inoperative. That TD25C would have had much tighter tolerances than those old gas engine jugs so I would guess at somewhat more than just ONE egg cup full - like maybe several good tea cups full over the time - although some of that would depend on the nature of the dust too, just how abrasive it was.

And I'm only a 'pore, dumm bulldozer operator', not a mechanic.

Just my 0.02.

Very open ended question - what says the 28 barrels were standard bore when placed on the twenty or were they already bored - well worn but in better shape than the originals?
Were the 28 barrels put on to increase the output of the engine? Change the displacement, raise the compression - etc?
Unless one has the entire history of the machine, it is all just guess work -
Those low compression engines were marvelous at being able to withstand very poor tolerances and still function.
Any signs or indications of heat or freeze damage to other parts - what is the condition of the lower end -- crank and mains, rod bearings, cam and bearings? How dirty is the crankcase -

I have seen air cleaners so full of dirt one had to dig the elements out with prybar, screwdriver and hammer, not just the outer element but the inner also. This was on a Ford 9000 wheel engine, a cleaned up air system, oil change and it went back to work, no oil consumption either. That shows how well the elements worked.
Incidentally the reason the machine came into the dealership - it had no power and was smoking badly!

Those "old" oil bath air cleaners were very marginal at best, the amount of "materials" that passed was dependent upon the maintenance and conditions of operation.
The amount of dirt that was accumulated upon the screen and tubing leading to the intakes will attest to the inefficiency of those systems.

In many cases - mechanics used what was available - nothing prevents using or mixing components as long as those do function. That would include using parts from one Manufacture to another. As an example --- I know of a Caterpillar Thirty that was very low on compression - rings were worn so badly --- the fix --- TD18A Rings - of course they were salvaged from an overhaul of the IHC too - but two to a groove in the pistons and compression improved greatly - to my knowledge that Thirty is still operational today and those rings were put in place well over 50 years ago. It worked 15 acres for many years that way and pumped water too.

CTS