Modified Tractors (MOD)
Updated: Jan 18
Weight is 7400lbs
Unless specifically outlined below in the class specific rules, the Tractor General Rules
and the overall General rules outlined above apply.
All vehicles must be a registered Modified Tractors to compete in this class.
1) All automatic transmissions must have: new six (6) strap approved blankets and
have reverse lockout.
2) All drivelines must be entirely enclosed in 5/16-inch steel or 3/8-inch aluminum
and securely fastened to the frame.
1) Total length of vehicle shall not exceed fourteen feet from center of rear axle with
wheel base at 11-foot 6 inch minimum.
2) No engine sheet metal.
1) Tire size shall not exceed 31 inches in width.
1) One (1) marine, or aircraft, or industrial type up to 2500 cubic inches with (12)
cylinder limit. Two (2) compression stages maximum. Allow EFI on V-12 Allison and V-
12 Packard. Rolls Royce Griffon limited to a maximum overdrive limit on the
supercharger to the high-speed ratio of 7.7 to 1. Turbocharger(s) on Rolls Royce
Griffins allowed single stage.
2) Two (2) automotive type engines, with maximum 14-71 blower (no screw type), no
overdrive limit, hemi type heads allowed. 650 cubic inch limit.
3) Three (3) automotive type engines with maximum 8-71 blower, limited to 43%
overdrive, no Hemi, Pontiac, Oldsmobile, Big Chief or Big Duke style heads, 650 cubic
4) Four (4) naturally aspirated automotive type V8 engines, any CID, any two (2)
valves per head, carburetors or fuel injection.
5) Turbine engine or combinations of turbine engines are allowed maximum military
rating of 4380 HP. Any engine or combination of turbine engines with HP rating of
3750 or less are allowed water/methanol injection. Nothing allowed to be sprayed or
injected in the airstream of the intake or turbine engines that total more than 3750
horsepower. All turbines to have over-speed safety devices set to a maximum of
6) All boosted V8 motors limited to a maximum 5” bore spacing.
RRTTPA recognizes the following turbine engines for use in RRTTPA competition and
their horsepower ratings are as follows: (No turbine engines other than those listed
may be used.)
Pratt & Whitney
T53L1 = 825 hp
JFTD12-4 = 3430 hp
T53L3 = 920 hp
JFTD12-5 = 4050 hp
T53L5 = 960 hp
JFTD12A = 4050 hp
T53L7 = 1100 hp
T53L11 = 1100 hp
T53L13 = 1400 hp
T55L1 = 1600 hp
T55L5 = 2200 hp
T55L7 = 2650 hp
T55L7C = 2850 hp
T55L9 = 3750 hp
T55L11D = 3750 hp
T55L712 = 3750 hp
6) Any Turbine engine must have a minimum of 3/8 inch streel shielding around the
hot section if it is under 1500 horsepower. Any engine over 1500 horsepower will
have a 1⁄2 inch steel shielding. No blankets.
7) Two (2) 1710 cid Allison aircraft V12s, with a maximum overdrive limit on the
stock Allison supercharger of Ø9.5” to a maximum speed ratio of 8.8:1. No
8) Any motor combination not already mentioned in the rule book must be approved
by the RRTTPA Board.
9) Must be a minimum of two (2) supercharged V-8 engines, turbocharged or
supercharged industrial engine or turbine or combination of turbine engines of 2850
horsepower to compete at an RRTTPA event.