Small Block Rules
WEIGHT: 6000 #
TIRES: 18.4 x 38 maximum
AGE OF DRIVER: 16 years or older, under 18 years must have parental consent.
AGE OF TRACTOR: 1972 and older, no home- made tractors
FUEL: No pressurized fuels, no nitrous oxide, no nitrogen methanol, and no propylene oxide. Racecar gasoline, Alcohol, and oxygenated fuels may be used.
DRAW BAR: Drawbars must not exceed 20 inches in height or less than 18 inches from center of axle to hooking point. No part of draw bar may extend rearward beyond point of hook. No part of drawbar is to be attached to any point higher than the center of rear axle. Drawbars must be stationary in all directions. No clevis, absolutely no turnbuckles.
ENGINE RULE: Must be 410 cubic inches or smaller, 6 cubic inches may be added to engines that require a fresh re-bore, no engine may be larger than 416 +0 cubic inches, Must be an industry standard small block, no big blocks. Must be a cast iron block, cast iron heads, maximum eight cylinders, two valves, one spark plug per cylinder, Camshaft in block.
MANIFOLD, CARBURETOR: One four barrel naturally aspirated carburetor, 4150 base, 750 CFM. No predators, no dominators, no aerosol carburetors. No fuel injection, no throttle based injection. Carburetor will be inspected with a No Go gauge (1.400 top and 1.700 bottom. All intake manifolds can be low-rise type. No tunnel-ram, no sheet metal/ aluminum intakes, no casted sheet metal type, no welded manifolds allowed. Headers must exit in an upward direction.
IGNITION: All ignitions must use a MSD model 6AL or 7AL-2 system with an RPM limiting chip. Tech inspections performed by using MSD model 89952 RPM Module/Chip Tester.
1) Tractor engines will have an 8000 maximum RPM limit.
2) Tractors must use an MSD model 6AL or 7AL-2 system with chip limiter.
3) Boxes must be easily accessible for officials to tech.
4) Boxes may not be tampered/ modified. Rivets must be original. If you drill a rivet out, you will have to buy a new box. If factory sealant/ sticker is broken, a new box is mandatory.
5) Only the wiring per MSDs wiring diagram is allowed, and must be plainly visible. No other wires may be attached to any of the MSD factory wires other than as specified per MSDs wiring diagram.
HOOD, GRILL, TRANSMISSION, REAR END, AXLE: All Sheet metal to include Hood, Grill, Fuel Tank, (if part of sheet metal) Side metal, and Screens must be for that make and model and must maintain original dimensions in all directions (width, height and depth) but could be moved forward a maximum of 8 inches as a complete unit/assembly. Sheet metal must be 1972 or older. Some sheet metal modifications are allowed contingent upon Hot Rod committee approval. Agricultural rear ends must also be 1972 or older. Crossing Sheet Metal with Different Manufacturer is permissible. Bell housing and transmission may be removed if they were designed to be unbolted from the rear end at the factory. Front ends may be homemade, maximum allowable wheelbase of 100 inches from center of rear axle to center of front axle or manufacturer stock length if greater than 100 inches.
TOTAL LENGTH OF TRACTOR: Tractors maximum allowable length is 11 inches from center of rear axle to the furthest point forward, including weights.
SAFETY EQUIPMENT: Helmet and fire suit, wheelie bars, ski bars, kill switches, fire extinguishers, fenders, SFI damper, SFI flywheels and pressure plates, SFI bell housings, engine side shields must be incorporated. Drive shaft from bell housing to transmission must be shielded. Roll cages must be capable of supporting tractor and driver. No steel fans. All tractors must have wide front axles with a minimum of 32 inches between inside of tires. All electric fuel pumps must be wired to the kill switch. Neutral safety start switch is required. NO factory cast iron tub frames allowed.