|Single Engine Modified Tractors
Class Rep: Ken Austin
Weight: Not to exceed 6100 lbs
Drawbar Height: 20 inches maximum from top of hitch
Drawbar Length: 18 inches minimum from center line of rear axle
1. A maximum of one 8 cylinder engine of 575 cubic inch displacement,. One spark plug per cylinder.
2. Modified tractors are allowed to run on alcohol or gas. (Naturally aspirated carbureted or injected). No
electronic fuel injection allowed. No oxygenated fuels.
3. Electric fuel pumps are allowed but they must be wired to the kill switch.
4. All engine exhaust must exit upwards and be a minimum of 12 inches long above the bend in the pipes.
5. No engine driven fans. Alternator must be shielded 360 degrees with 1/16 inch metal.
6. All engine dampers to be bolted to the crankshaft and be shielded 360 degrees with 1/4 inch metal in a circle
around the outside diameter of the balancer or SFI approved balancer.
7. Throttles to be a positive two-way deadman type. All foot throttles must have a toe strap.
8. Engine outside shielding must extend from the base of the head to 2 inches below the bottom center of the
crankshaft throw. Frames are acceptable.
9. Maximum tire size is 30.5 (rear tire). Radials are permitted.
10. Fenders on all tractors must be constructed so that no part of the driver's body can come in contact with the
11. All tractors must be no longer than 14 feet from the center of the rear axle forward.
12. No tricycle front ends.
13. Weights must be securely fastened on brackets and not extend rearward beyond the tires and not on tractor
platform. Weights must not obscure hitching procedure.
14. All modified tractors must have 2 supports of sufficient strength bolted to the underside frame and differential to
prevent to tractor splitting.
15. Stabilizer bars must extend minimum 2" beyond the edge of the rear tire. Stabilizer pads must be minimum of
24 square inches each. The pads to be mounted maximum height of 8 inches off the ground when the tractor is
parked on a flat surface. The pads must be a minimum of 24 inches from the outside edge of one to the outside of
the other pad. Vertical bars to extend up the rear edge of the pads, minimum of 12 inches, made from equal
strength as the stabilizer bars. Stabilizer bars must be capable of supporting tractor's weight of the heaviest
class that it will pull in. No wheels are allowed.
16. Drawbars to be fastened no higher than center pf rear axle on differential housing.
17. All drive shafts must be shielded 360 degrees with a minimum of 1/4 inch metal. Inside diameter not to exceed
2" more than the outside diameter of the largest universal joint. Shields must be bolted together with 3/8 inch
bolts or larger, with a minimum of 3 bolts down each side, no more than 6 inches apart. Bolts to be grade 5 or
18. All tractors must have a switch that will allow starting in neutral or park only.
19. All tractors must have an emergency kill switch that will kill the engine in the event of breakage with a ring on the
switch no less than 2 inches in diameter located at the rear of the tractor.
20. Modified tractors must have an automotive type white light on the dashboard and one within 6 inches of the kill
switch to indicate when the tractor is in reverse position.
21. All tractors must have a 2 /2 lb fire extinguisher convenient to the driver and be compatible with the fuel being
22. All drivers must wear a complete fire suit (minimum requirements single layer fire suit, fire gloves, balaclava,
fire boots or leather work boots). No leather running shoes allowed. Seatbelts are mandatory and must be worn.
23. Standard transmission must be a steel bell housing, complete with 3/16 inch block plate and 90 thou thick liner
recommended. Clutch and flywheel must be SFI approved. Owners must sign a guarantee of compliance and
24. All automatic transmission tractors must have a reverse lockout. Automatics must be protected from back of
block to rear of planetaries 360 degrees.
25. All modified tractors must have a roll cage. The tube diameter must be minimum of 1 5/8 inch and a minimum
wall thickness of .083 inch chrome moly or 118 mild steel. Cages must be constructed to be able to support the
weight of the tractor.
26. All general rules apply.