LIMITED PRO STOCK TRACTORS
SUPER FARM TRACTORS
LIMITED PRO STOCK / SUPER FARM TRACTORS 2025 - GENERAL RULES
- Maximum Weight: 8,700 lbs.
- Cubic Inch Limit: Maximum of 540 cubic inches.
- Overhead Cams: Not permitted.
- Engine Head: A recast head for the series engine is permitted.
- Rear Ends: Component rear ends are prohibited.
- Aluminum Heads: Not permitted.
- Exhaust Manifold: Any exhaust manifold is allowed.
- Fuel: Only diesel fuel is permitted.
- Fuel Containers: Pressurized fuel containers are prohibited.
- Turbocharger: One (1) turbocharger is allowed with necessary manifold modifications. Manifold pressure may be a single (1) stage only.
- Injector Pump: Legality determined by visual inspection of the external housing (not inner workings).
- Pump Specifications:
- Only one (1) plunger per cylinder and one (1) injector per cylinder is allowed.
- Pump Restrictions: No Sigma or MW pumps. Only ‘A’ and ‘P’ pumps are permitted.
- Exhaust Side of Turbo: Maximum 4.5” outlet I.D. for Limited Pro Stock G-Trim.
SUPER FARM TRACTORS
- Maximum Weight: 9,500 lbs.
- Cubic Inch Limit: Maximum of 640 cubic inches.
- Engine Head: OEM stock head for that model or series engine.
- Manifolds: OEM stock intake and exhaust manifolds for that model or series engine.
- Intercoolers: Permitted.
- Overhead Cams: Not permitted.
- Components: Component tractors are prohibited.
- Fuel System: Only a P-pump with one plunger per cylinder is allowed.
- Turbocharger:
- Size: Turbo must be 3” x 3”.
- Altering the turbo housing to accommodate a smaller foot or base is prohibited.
- Exhaust Housing: The bolt pattern must not exceed 2.75” x 3.5”.
- Intake:
- Map width enhancement is allowed.
- Compressor wheel must protrude into the three-inch bore.
- Compressor housing must be no larger than three inches in diameter at the face of the wheel.
- Exhaust:
- All turbine wheel blades must protrude into the three-inch bore. All air must exit through a 3” opening.
- Exhaust housing must be no larger than three inches in diameter.
- The exhaust housing will be measured at the intersection of the turbine wheel face and the tip diameter.
- Waste Gates: Not permitted.
- Variable Geometric Turbochargers: Not permitted.
LIMITED PRO STOCK / SUPER FARM TRACTORS 2025 - GENERAL RULES
- Roll-Over Protection: All tractors must meet 47.1 SFI Spec roll-over protection standards.
- Safety Uniform: Full driver safety uniform is required.
- Harness: A five (5) point harness is mandatory.
- Hitch Height: The tractor must have a hitch height of 20 inches.
- Tire Size: Maximum tire size allowed is 24.5.
- Chassis: Must use an OEM Ag Chassis (Component tractors are prohibited).
- Clutches: Only mechanically activated clutches are allowed. No cast iron clutch components or flywheels.
- Clutch Blankets: Must meet SFI Spec. 4.1. Blankets should cover the full bell housing, with a minimum six (6) inch overlap where fastened.
- Side Shields: Must be solid and made from at least 1/8” aluminum or .090” steel.
- Rear Tire Shield: A solid shield must separate the driver from the rear tires, designed to support the weight of the driver.
- Air Shutoff: Must consist of a cap that closes over the air intake pipe and must be spring-loaded to the closed position.
- Kill Switch: Must be securely mounted to the back of the vehicle, with a 2-inch diameter ring (at least 1/8” thick) for sled attachment. Must also be operable from the driver’s seat.
- Stabilizer Bars: Must be rigid and support the vehicle weight for the heaviest class. The bar should extend a minimum of 32 inches behind the rear axle and be no more than 10 inches off the ground.
- Exhaust Wheel Cage: Made of stainless steel, bolted to the exhaust housing, with a minimum of 8 – 5/16 bolts.
- Exhaust Pipe: Two (2) ½ inch Grade 5 bolts or a containment star must be installed within two inches of the exhaust wheel, installed 90 degrees to each other.
- Intake Protection: A Kevlar-lined containment device (bag or blanket) must completely enclose the intake compressor housing. The device must be commercially available from the USA.
- Fire Extinguisher: Must have a 2 ½ lb. dry chemical fire extinguisher, securely mounted and within reach of the driver.
- Ladder Bars: All tractors must be equipped with ladder bars.
- Fuel Sampling: Diesel-powered vehicles must have a fuel sampling valve on the return line from the fuel injection pump. The diesel engine must be running when the fuel sample is obtained. For 2025, the diesel fuel test range is between a minimum of 30 and a maximum of 150.
- Water Injection Sampling: Diesel-powered vehicles must also have a water injection sampling valve. If none exists, the tank line must be unfastened to obtain a sample.
- Fluids Testing: All fluids are subject to diagnostic screening.