6,500 Classic Modified (FPP Rules)
For the 2025 Midwest Winter Nationals: we will allow MAX RPM up to 6500 and we will allow componet chassis to allow the Central Ohio tractors compete.
AGE OF TRACTOR: Tractor must be 1972 or older and be an agricultural two-wheel drive tractor. No industrial or experimental tractors.
CHASSIS
1. Rear end, transmission, and axle housing must appear stock. Transmission shafts must remain in stock location. No differential locks permitted in the rear end. No power shift, factory TA permitted. Double clutching is prohibited.
2. Engine must be parallel with the input shaft of the transmission and be mounted in the center of the frame.
3. Maximum overall length, including weights measured from the center of the rear axle, is 12 feet. Tractor wheelbase may not exceed 102” from center of rear axle to
center of front spindles.
4. Sheet metal must be stock appearing dimensions. Must be in stock location as measured from the centerline of the rear axle. Sheet metal can be from a different
tractor and must be older than 1972.
5. Roll-over protection must extend higher than the driver’s helmet.
6. Front Skids are recommended in 2022 and will be mandatory in 2023.
CLUTCH
1. Pressure plate must be competition type and meet SFI approved 1.1, 1.2, or 1.5.
2. Tractors built prior to 1/1/2006 must have a steel constructed flywheel of greater than 1 1⁄4 “maximum thickness. Cast iron flywheels are not permitted. Flywheels
must be accessible for inspection. Tractors must have a steel shield around the flywheel and clutch with a SFI blanket with a minimum rating of 4.2. The shield must
be made of .25” (1⁄4”) minimum thickness and minimum with equal to the thickness of the flywheel and pressure plate assembly. Shield may be attached to the bell
housing, engine, or chassis.
3. Tractors built after 1/1/2006 must have a SFI rated competition designed flywheel, clutch, and pressure plate. Tractors must also have a steel bell housing with
SFI rating of 6.1, 6.2, 6.3, or a SFI rated blanket with a 4.2 rating
.
ENGINE
1. Engine must be naturally aspirated V-8, with a cubic inch displacement no larger than 521.16 c.i.
2. Block must be cast iron, no aluminum.
3. Cylinder heads maybe either cast iron or aluminum.
4. Single carburetor, no fuel injection, no turbo chargers or forced air induction of any kind. Air cleaners must be under the hood.
5. Aluminum manifolds are permitted.
6. Headers must exit in an upward direction.
7. Spark plug guards must be in place to deflect downward or contain spark plug.
8. Crank driven engine cooling fans must be a minimum rating of 8,000 RPM or electrically driven.
9. Maximum allowable RPM’s will be no greater than 6500. All ignitions must use an MSD system with a 6500 maximum RPM limiter chip or limiter box. Must be equipped with a recall tach. No more than 100 RPM variation over 6500. If a check and tach recall is cleared, it is an automatic disqualification. If the tractor is over 6600 RPM’s tractor can be checked with handheld tach as a backup for accuracy.
10. A Recall tachometer must be mounted on the driver’s side (left) of the vehicle for ease of checking fom the ground. Tachometers will be cleared during tech prior
to the event. Officials reserve the right to check the RPM’s on each tractor or randomly at events.
11. No computers allowed that control any mechanical operation of the competing vehicle. No automated or computer operation of traction control devices. The use
of electronic control devices for ignition timing I.E. (MSD 8973, Power Grid, Six Shooter, and Davis Electronics, Etc.) are not allowed. Wiring of any components
(Tach, Coil, and MSD Box) must be readily visible for inspection.
12. All engines must be controlled directly by the driver through a manual throttle.
FUEL
It is recommended that the fuel tank be mounted in front of the tractor. Gasoline fuels only with a maximum of 750 specific gravity, no alcohol, no pressurized fuels, no
nitrous oxide, no oxygen accelerate, no nitrogen methanol, and no propylene oxide. Race Car gasoline may be used. Diesel conversions are allowed but must run on
gasoline with no injection.
18.4 x 38 maximum allowed bias or radials with any cut.
WEIGHT
Maximum weight of 6,500 lbs.
HITCH
Hitch Height is 20 Inches