Glenn; thanks for the kind (and very true) words on the AC D-21 SII. I know for a fact that a STOCK, factory D-21 3500 diesel engine can crank
out 275 PTO horsepower; because I was the mechanic
operating the PTO dynamometer;shortly therafter the D-21 twisted the PTO connecting shaft off the dyno; took me 3 months to rebuild it.I was going TOWARDS FULL throttle on the D-21 when the PTO C/shaft sheared, I was at 2100 RPM when the dyno read 275 hosepower. It takes more than just increasing the d/fuel to get these engine to make this kind of HP; most old, tired stockers will just come apart at the bottom end; I did it one time years ago; when I was younger and more stupid. I trashed the D-21 engine in the process because the crank broke and came out the side of the block sideways; good thing I was up in the tractor seat; crankshaft on a Seies II weighs 320 lbs w/flywheel!!!!