Unless the piston rings are totally worn out, there's a quick, simple, and inexpensive way to reduce smoking to an acceptable level, if not eliminate it altogether. Instead of doing a major overhaul, Do an oil change with fresh 30 weight oil (straight weight, not something like 10W-30) and add 2 or 3 quarts of Diesel fuel to overfill the crankcase. This will allow the crankshaft and connecting rods to splash down into the oil/Diesel mix, and churn it around like the agitator in a washing machine. Run the engine for about 30 minutes at a fast idle- - - -1500 RPM or so. DO NOT DRIVE THE VEHICLE OR PUT ANY LOAD ON THE ENGINE! Afterwards, drain the oil while it's hot, change the oil filter if there's one onboard, and refill with fresh 15W-40 oil.
If your smoking problem is caused by sticky piston rings, the flush will dislodge the crud behind the rings and allow them to re-seat themselves against the cylinder walls. If the flush doesn't help, you will have done a much better internal cleaning prior to a rebuild than any amount of brush and solvent work can accomplish. Win/Win! Several stovebolters have done this procedure and have been very pleased with the results. If it doesn't work, the total cost is nothing more than an oil change and a little bit of Diesel fuel. Good luck!
Jerry
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