That's "the Making off..." our John Deere 4430 from 1972. We bought that Tractor in France and rebuild it. We tuned him up a bit too for Tractor Pulling. He competes in the 4.5ton Sportscategory. Specifications original: 6,6l 6 Cylinder Turbocharged engine 125hp Weight: over 5 tons The Changes we have done 2007: Decreased the compression to 14,5:1 Put a Holset HX 50 Turbo on Flowed Cylinder head Bigger inlet-valves and stronger springs Injection:13mm elements in a Bosch A Pump Combined the pto and drive clutch by welding the two shafts together Taking all the pto-stuff out wich is not used anymore Estimated Power: 350hp Setup 2008: Rebuilding Clutch Rebuilding Camshaft Gearboxwork Power 2008: 450hp ??? More News: www.tractorpullingzimmerwald.ch Thanks for your comments... If there are questions... just ask.