Here are the rules copied from the NTPA website: Pro Farm Class Note: The Pro Farm class will run under NTPA Super Farm division rules, plus the following rules. This class be only sanctioned at State and Regional level A. Engines 1. No engine larger than 466 cid. (+ or � 1 percent) Diesel fuel only 2. Engine head must be OEM agricultural-type (no aftermarket head) for that brand engine. 3. No overhead cams allowed. Maximum 2 valves per cylinder 4. Only Manifolds allowed must be OEM rubber tired agricultural type manifolds for both intake and exhaust. 5. Turbo restrictions: Turbo must have a 3 inch maximum ID pipe with a 3 inch minimum length before and after the turbo no more than 3 inches from the face of the wheel. All inlet and exhaust air must flow through this restriction, 6. The maximum allowed size pump for diesel injection is a p-pump. (No aftermarket housing). Only one plunger per cylinder allowed. B. Competition Pro Farm tractors are only allowed to compete in the Pro Farm class. C. Tires Maximum size of 20.8 x 38 non-radials with a maximum of 56 lugs allowed, Tire can be no larger than a maximum of 220 inch circumference when inflated to 20 psi. Tread width not exceed 21 inches when mounted on a 20 inch wide rim. Tires must be mounted on steel rims only. (No aluminum rims on rear) D. Weight This class shall compete at 10,000 lbs. E. Safety All OEM chassis (non-component) Pro Stock rules, including shielding, safety and SFI requirements, apply to this class.
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