Smoking H.

Pull it down and start measuring and checking. It could be stuck or worn rings, worn sleeves, worn valve guides or a combination of the above.

You can do everything without taking the engine out or splitting the tractor. I do suggest however that if you do more than just rings that you pull the motor and get the block cooked out at a machine shop. These old girls have been around a long time and have been overhauled just as you propose to do many times. Your engine could possibly have collected a lot of crap in the water passages which inhibits coolant flow to the head. They are also noted for cracking heads which I and my machinist have theorized is related to the above crap in the block. The down side to this is that it will cost you more $ for cam bearings and the cleaning. Just something to think about.