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Multi Engine Tractors

Class Reps – Peter Robinson
Weight not to exceed 7,900 lbs.
Drawbar Height 20 inches
Drawbar Length 18 inches

The following engine combinations are considered “maximum limitations” for vehicles that compete in this class.

       1.     Four (4) blown automotive engines with 8-71 superchargers at the overdrive limits listed below or single staged turbocharger.  No intercooler allowed the port-fuel injection only.                                      

                A. Wedge heads that will accept a stock OEM intake manifold bolt pattern limited to 70% maximum overdrive.                                                                   

                B. Big chief or any wedge head without a stock OEM intake manifold bolt pattern are limited to 50% maximum overdrive.                                               

                C. Hemi Heads are limited to a maximum of 45% overdrive.

 2.        Three (3) blown automotive engines, with 14-71 superchargers at 70% maximum overdrive or single staged turbocharger.  No intercooler allowed, with port-fuel injection only..

       3.        Five (5) naturally aspirated Big Block automotive engines.

       4.        Six (6) naturally aspirated Small Block automotive engines.

       5.        One (1) Allison engine with twin turbo or auxiliary stage plus one (1) blown automotive engine with a 8-71 blower limit.

       6.        Two (2) Allison engine with a maximum of two staged supercharger or turbocharger, injected or carbureted.

       7.        Two (2) industrial or marine-type engine, twelve (12) cylinder limit.   Diesel allowed, may have a maximum of two (2) compression stages.

       8.        Combination of Ntpa recognize turbine engines not to exceed a maximum of 5800 total horsepower using the ratings as approved by Ntpa listed below.

       9.        All automotive engines may run a maximum of 2 valves per cylinder and are limited to 1 spark plug per cylinder. 

      10.     Note:  You may carry more engines than the maximum number allowed in the 7500lb modified class as ballast, but must disable extra engine’s position.  Same engine’s position must remain disabled for that session.

      11.     Note:  Any combinations require 9 or more cylinders running.

General Rules

1.        Rear brakes are mandatory.

2.        All drivelines must have 3/8-inch steel, 360 degrees around brake components, and both ends must be closed with 1/8 inch, or greater, steel.

3.        Tractors are required to have a reverse safety light system.

4.        A white light automotive quality, a minimum of 2 inches in diameter, must be mounted directly above or below the safety kill switch at the rear of the vehicle.

1.        A light in the driver’s compartment must be operated off the same system

2.        Both lights are to be activated by a shift lever such that it will be lit only when the vehicle is in reverse.

3.        Pulling vehicles must be equipped with an operation starter interrupter switch on the gearshift that will allow starter engagement only in a neutral gearshift position

4.        Vehicles are required to have 9 cylinders or more to pull with class.

Kill Switch

1.        Tractor must have kill switch mounted independently of drawbar and or wheelie bars.  Kill switch must be located in the rear center of the vehicle a maximum of 6 inches off center in any direction and must be 48 inches above point of hook.

2.        Automotive engines, Allison aircraft, marine, industrial engines, turbine engines, that are spark ignition must use a waterproof, dustproof tether type safety stop switch. 

3.        Kill switch on spark ignition engines, must break or ground the ignition circuit.  On vehicles that have spark ignition engines and electric fuel pumps kill switch must also break current to the fuel pump.

4.        Kill switches must have a minimum 2 inch diameter solid ring.  Ring can not be less than 1/8 inch cross sectional thickness’ attached to them.  Sled cable must attach to this ring.

5.        Kill switch ring must be secured with a single nylon tie wrap.   

6.        Portion of kill switch and mounting bracket must be able to withstand 32 pound of pull per switch when pulled.  All single pin breakaway kill switches must be able to pivot left or right of center.

7.        Ignition engines must have a bar type master shutoff switch within easy reach of the driver.

8.         

Safety.  & Roll Cage

1.        Multi engine tractors must have a roll cage with a five point driver restraint harness and driver seat mounted to the rollcage structure, independent to the tractor chassis.  The five point restraint must be a quick release design and be securely fastened during competition.. 

2.        Vehicle is required to have a quick release, removable or swing away steering wheel.

3.        Vehicle must be equipped with a minimum of 2.5 pound fully charged with working gauge dry powder type fire extinguisher.  Must be convenient to driver.

4.        Helmet must be a Snell approved 2000 or newer

5.        Driver must wear a minimum protective clothing of SFI 3.2-1 driving suit with a balaclava.

6.        Driver must wear a full 360 degree neck collar meeting SFI spec 3.3 or Hahn’s device.

7.        Helmet with flame retardant lining and flame retardant neck skirts are allowed.   If helmet with flame retardant lining and flame retardant neck skirt is worn no head sock is required.

8.        Drivers must wear the following full protection under competition:  1. full face helmets with shield.  2. Head sock. 3. Fire resistant single layer nomex gloves.  4. Fire resistant shoes with no leather boots acceptable.

9.        Vehicle must have a driver in the seat at all times when running or being started.

Seats and Fenders

1.        All vehicles must have a strong rigid seat and fenders.

2.        Fenders to consist of barrier between driver and tire.

3.        Fender to be a minimum of 1 inch over height of tire.

4.        Fender to curl 4 inches horizontally from vertical edge over the tire in the same configuration as the tire, minimum length of 18 inches at top of fender.

5.        Fender must be able to support the weight of the driver.

6.        Fender or tire shield must be constructed so that when the driver is seated and his hands are on the wheel, he cannot touch the rear tire with any part of his body.

Stabilizer Bars.

1.        The bar must extend a minimum of 32 inches behind a ling drawn from the center of the wheel to the ground.  Pad must not be more than 10 inches off the ground.  At 32 inch point and to be measured during hitch check before competition.  The stabilizer pad must be a minimum of 5 inches square. With a minimum of 20 inches allowed from the outside of one pad to the other.

2.        Stabilizer bar and bar assembly is not to be mounted to the drawbar and drawbar assembly.  Stabilizer bar system must be able to support the weight of the tractor in the heaviest class pulled.  Jacking up the pads so the tractor is completely off the ground is a good test of the strength of the systems support ability.

3.        No crossbars between stabilizer bars allowed behind point of hook.

4.        Modified tractors where the hitch and wheelie bars are connected to the same frame the wheelie bars must be fastened at least 4 inches ahead of the hitch.

Clutches, Flywheels, and Automatics

1.        Torque converters, automatic shifts, etc. are permitted

2.        If used, torque converts and automatic transmissions must be equipped with an SFI 4.1 blanket.  Blanket must extend from rear of engine block to front of tail housing.  It must be fastened forward securely with two straps on each side, one above the crankshaft centerline and one below the crankshaft centerline.  Blanket should have a 6 inch overlap.  Straps must be 2 inches wide, with not more than 1 inch space between each strap.

3.        Competing vehicles that use an automatic transmission met be equipped with a positive reverse-gear lockout.

4.        Vehicles using a clutch will be required to have an SFI spec 1.1 or SFI 1.2 steel plate or steel billet flywheel or aluminum.

5.        All clutches and bellhousings must be SFI approved and inspected annually.

6.        All Lenco-type planetary transmissions, excluding reverser, must be covered with an SFI 4.1 approved blanket. 

7.        Clutch automatics: clutch must be SFI 1.1 or SFI 1.2 approved.  Automatic to be covered with SFI spec 4.1 blanket from back face of bellhousing to the tail shaft.

8.        Bellhousing must be originally purchased and initially installed as SFI 6.2 or 6.3 bellhousing with SFI sticker in place.

9.        Inspection/maintenance hole in bellhousing shall not extend farther forward at it top edge than flush with the cross-shaft hole, or farther downward at it bottom edge than to allow one 1/2inch bolt diameter edge distance for the fastening holes in both the bellhousing and the inspection cover.

10.     The length of the inspection hole shall be no more than 8-1/2 inches measured in a straight line and the ends of the hole shall be smoothly and fully radiuses to produce an oval shape.

11.     Bellhousing cover There must be (12) 5/16 inch grade #5, or better cap screws securing the cover to the bellhousing.

12.     The cover must have a plate or fillet that fits flush inside of the housing.

13.     The cover and fillet must be steel.

14.     The fillet must be welded to the cover and all bolts must be flush to the inside.

15.     6 bolts 3/8 inch minimum diameter used to secure the transmission to the bellhousing.

16.     All bellhousings must be flush on the inside surface.

17.     All automotive type engines with bellhousings and clutch will run a full block plate, either a unit commercially available., or minimum 3/16 inch steel, or minimum ¼ inch aluminum with 6 3/8 inch grade #5 bolts evenly spaced on the bottom of the bellhousing.

Chassis

Modified tractors that have the frame bolted to the transmission shall also have the frame bolted to the axle housing to prevent splitting of the tractor.  The frame must be of sufficient strength that even when the bolts from the plate of the transmission or rear end are removed, the frame still supports the weight of the tractor in the heaviest class being entered.

1.        No part of vehicle may extend more than 9 feet 6 inches when measure vertically from ground level.

2.        Tractors must have wide front axle.  Front wheels shall track with in the rear wheels.

3.        No dirt deflectors or mud flap devices allowed behind tires.

Drawbars

1.        Drawbars will be constructed so that in the event of breakage the supports do not pull from a top link or brace above the centerline of the real axle of the vehicle.

2.        Drawbar hold up device above the centerline of the rear wheels must have a single pin breakaway-type slide out drawbar.  The holdup device is to be within 6 inches maximum forward of the hook point.   Drawbars must have a device to support the drawbar from side to side motion a minimum of 6 inches forward of hook point.

3.        Drawbars must be rigid, with no movement allowed.  Drawbars must have the pivot pin on the same plane as the hitch point and parallel to the ground within 1 ½ inches, plus or minus, per foot of length. Legally allowed 10 degrees or less of drawbar angle.  Drawbars must be parallel to the ground.

4.        Drawbars must be steel.  Drawbars to be a minimum of 1 inch thick.

5.        Drawbars must be a minimum of 3 sq in total steel material.  This includes the area of the pin with the pin removed.

6.        The pin can be no less than 1 inch.

7.        Drawbars must be equipped with a steel hitching device not more than 1 ½ x 1 ½ square and not less than 1 ¼ x 1 ¼ square. With an oblong shape of 3 3/4 inch long x 3 inch wide with a maximum of 3 ¾ round.

8.        No portion of the vehicle can interfere with sled, chain, or hook during a pull or while being hooked or unhooked.

9.        Area 5 inches wide and 12 inches high immediately above the drawbar must be free of obstructions.

10.     The hook point will be an oblong shape of 3 ¾ inch long x 3 inch wide with a maximum of 3 ¾ round opening with 3 inches clear area from front of the hole to the rear of the drawbar.

11.     Hitch must be painted orange.

12.     Do not connect drawbars and wheelie bars.

13.     Vehicle must have a tow hitch on the front.  Tow hitch may not extend no more than 6 inches beyond the farthest front portion of the vehicle. Tow hitch must have a 3 inch diameter hole. 

Driveline/Driveline Shielding

1.        No drive shaft over 48 inches long allowed.  No input or output shaft that attaches to drive shaft may extend more than 4 inches beyond a bearing.

2.        A minimum of 1 inch material between the bolt and end of the drive shaft shield.  A minimum of 1 inch material to be in pilot holder at each end of the drive shaft shield.  A minimum of 8, 3/8 inch (grade # 8) bolts to carrier bearing assembly if attached to a vertical plate.

3.        All carrier bearings must be approved by Great Lakes.

4.        Multi engine tractors with inline engines that use a starter ring between engines.  The starter ring must be completely covered and securely fastened, and both ends must be enclosed the ¼ inch steel or greater.  If an engine block plate is used,  it is to be used for only the back behind starter ring portion of this shield

5.        All multi engine gear boxes are required to be minimum 1 inch billet aluminum or ½ steel thickness around circumference of rotation gears.  Any gear box less than minimum specified thickness may use the following to get full thickness required.

6.        Wrap billet aluminum gear box radially 360 degrees with webbed, tow strap type material to minimum of 1inch thickness. 

7.        Wrap billet aluminum gear box radially 360 degrees with steel strap to achieve minimum 1inch thickness.  Strap to me a minimum ¼ inch steel.

8.        Add a minimum ¼ inch steel strap radially 360 degrees and fastened within 1/8 inch of gear box to achieve minimum ½ total thickness of steel gear box.

Tires

1.        Tires no more than 30.5 inches X 32 wide with a maximum of 210” circumference, when inflated to 10psi.  Tread width not to exceed 32 inches.