135 wet stacking

a while back I brought home a diesel mf 135. used it on and off for a bit, but thought it was kinda underpowered. while brush hogging the back field , I happened to look back and saw some sparks coming out of the muffler. I parked the tractor until I had some time. I got the tractor in the shop, repaired some leaking fuel lines and took the muffler off. it appears to be the original muffler, with heat shield. the muffler appears to be plugged. no problem as I wanted to convert to vertical exhaust. took oil bath air cleaner apart. the amount of sludge on the steel wool was about 3 inches up from the oil. cleaned it up, and put it back together. anyway today I tried mowing with it again. the difference in power was amazing. however i'm getting sticky back oil out of the muffler. smokes quite a bit idling as well. when working the tractor at pto speed mowing, exhaust is clean, very little smoke. tractor has 7k hours on it, and has probably seen better days. if I use the tractor for some plowing next spring, and work it hard will that help fix the wet stacking issues? with the muffler plugged and the intake restricted, I can only imagine what the top of the pistons and valves must look like. do you think a set of injectors would help it any? thanks for the help.

Wet stacking is made worse as the engine wears and compression heat lowers. At rebuild time pay CLOSE ATTENTION to the cylinder head, install new seats and valves if needed to bring it back to new spec. DON'T just grind the valves and seats as that lowers the valves AND compression heat EVEN with new sleeves and pistons. I prefer to set the valves closer to flush with the head long as there's clearance during the valve overlap. Higher compression makes for an easier starting engine that burns cleaner too when cold.