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Limited Pro Stock Diesel Garden Tractor Class Rules
All general safety rules apply.
(1) Engine must be commercially produced with at least 1000 units built. Engines may be no more than 3 cylinders. May be liquid or air cooled. Engine block must have factory casting model and serial numbers visible and not ground off. Ag or industrial engines only; no automotive or motorcycle engines. No cut down 4 cylinder engines allowed.
(2) Engine will be no more than 70 cubic inches. This is based on the factory casting numbers. No sleeving down or de-stroking larger engines.
(3) Water injection will be allowed. Must be plain water only. Combustible agents (alcohol, oxygenators) are NOT allowed in water injection. Soluble oil Lube additives are permitted.
(4) Engine modifications are permitted = Rods, Pistons, Cam, Fuel system.
(5) Engine must have OEM intake manifolds and exhaust manifolds, polishing is permitted. No tube headers or intakes.
(6) Head work is permitted on stock OEM heads. No Billet heads. No overhead cams. Must be indirect injection. No converting from indirect to direct. Injectors must remain in stock location.
(7) Injector and injector pump modifications allowed. No Billet injector pumps.
(8) Must be “Cam Box” or “PFR” injection pump. No electronic or common rail injection systems.
(9) Turbo charging is permitted, but limited to a single turbo only. Turbo will be fitted with a shut down guillotine on the compressor inlet side of the turbo. Exhaust “L” of turbo must have minimum of 5/16 cross in elbow with exhaust to discharge vertically.
(10) Electric fuel supply pump is permitted with positive power wire to have shut off disconnect at rear of tractor.
(11) No propane, nitrous injection or any type of secondary fuel system of any kind will be permitted.
(12) All tractors must be compression ignition and use Diesel fuel only. No spark plugs or alcohol as a fuel. Diesel fuel must be NTPA or NQS legal.*
(13) Stock frames, stock appearing frame rails, and tube frames are permitted. Tube frames must be covered with sheetmetal.
(14) This class is for stock appearing tractors with full hood, grill and side shields. Must be recognizable as an actual modern production garden tractor or small farm tractor. Hood and grille can be from a different make than frame/rear end. Has to look like a tractor.
(15) Must use garden tractor drive line components, modifications are allowed. Internal gears, front reduction housing and planetaries are allowed. No cut down automotive rear ends.
(16) Full metal side shields to cover engine area minimum 16 gauge steel or 14 gauge aluminum.
(17) Must run 5/16” cable around oil pan over top of valve cover in a complete circle connected with (2) cable clamps.
(18) Must run billet steel fly wheel.
(19) Clutch assembly and fly wheel must be surrounded 360 degrees with 1/8” steel or 3/16” aluminum. This is also to include cast iron front balancer pulleys. SFI approved front dampers need not be shielded.
(20) 56” wheel base maximum.
(21) Maximum 8 feet from center of rear axle to front most portion of weights.
(22) 13” hitch height.
(23) 26” x 12 x 12 tires max.
(24) 1100 lbs./1150Ibs.Weight classes.
(25) Must have wheelie bars same specifications as other classes.
(26) Kill switch device mounted on rear of tractor must disconnect power to electric fuel pump along with activating turbo guillotine.
(27) Dead man throttle required.
(28) Min. of 1 lbs fire extinguisher required.
(29) Helmet face shield or goggles required. Gloves are recommended.
(30) No belt driven cooling fans. Electric fans only.
(31) Intercoolers and ice boxes are not permitted.
*Diesel only with a dielectric value of no greater than 4.9 or less than 2.2. The dielectric meter shall use Cyclohexane to establish the zero reference point in determining all diesel fuel dielectric constant values. The use of additives containing oxygen, such as nitromethane, propylene oxide, dioaxane, MTBE, alcohol (methanol), or nitrous oxide is prohibited. These additives, and others of the oxygen-bearing family, will significantly change the dielectric values of diesel fuel.