the IH engine is a good engine. If you had records on when the water filter has been changed, and oil, that would help. I have seen that IH engines have over 5000 hrs , and still have no problems
Ran a 1486 tractor with 436 cube engine from new to 7700 hrs. till overhaul. A stuck compression ring on n1 with a little extra blowby signaled it was time to do something to it. Crankshaft was fine and went back in the same way it came out. This tractor did a lot of heavy work for years prior. IH engines are tough to beat!
had a 1460 with over 4000 hours-no problems and better than a gallon an hour easier on fuel than the 1660 with a cummins that replaced it. And no-the 1660 didn't do that much more work for the fuel it used-not even close.