Picked up a Farmall 450 gas this summer for taking care of the hay field. The previous had paid for a "valve job" on it~ 3 years ago, but I don't have details on exactly what they did. I'm seeing ~105-110 psi compression from each cylinder. Spark plugs are oily but not to the point of fouling out. It has a bit of a stumble at idle and light load. But most concerning, I'm going through a gallon of oil for every 10 gallons of gas. Exhaust looks pretty clean, a little smoke on startup, but cleans up by the time you close the choke. It looks like the rear main seal is leaking a little, but no wheres near that kind of volume. When running, the crank breather tube smokes like a son of a gun.
I'm thinking the piston rings are leaking enough to cause excess pressure in the crank case, but I'm a shade tree mechanic at best and would love some ideas from folks with more experience before I dump another grand into a rebuild kit for something like a clogged vent line.