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4x4 Pro-Stock Truck 6200# 

NK members elected to follow the Outlaw Pro Stock Rules


  1. Maximum weight is 6200#

    • Vehicles with engines over 485 cubic inches will lose 200 lbs of weight up front. 

  2. Maximum of one naturally aspirated engine with a 485 cubic inch limit. Engine must match sheet metal.

  3. Tires will be DOT approved and must maintain original tread pattern. Maximum tire size is 33.12.50. Tires will not track past 50% of front to rear width. NO BARRED TIRES.

  4. Vehicle will have stock frame. Air bag suspension is not to be controlled from inside the cab.

  5. Vehicle will have a 133” maximum stock wheelbase, any body style - including fiberglass with a protective firewall, one ton maximum front end, any size rear end. No flat bed.

  6. Vehicle will be limited to a single “ 1 piece” carburetor.

  7. No alcohol fuel allowed. Q-16 Fuel is allowed. No nitrous oxide or nitro methane. No ether bottles (starting aides) allowed on board while pulling. No ether start systems.

  8. Use of after-market fuel injection system is NOT permitted.

  9. Vehicle will be equipped with SFI steel bellhousing and block-saver plate. Must have shield around the clutch release hole.

  10. Vehicle may run any transfer case.

  11. Vehicle may use any cast iron block not exceeding 4.9 bore spacing. No aluminum block, Any after-market head having no more that two (2) valves per cylinder may be used. No hemi-heads. No sheet metal manifolds and no two-pieced or removable tunnel rams.

    •  Engine location must be no less than 14” from center line of front axle to front of bell  housing flange.

  12. Allow functional hood scoops with open back. Hood perforations will be allowed for exhaust only.

  13. Exhaust will discharge vertical or underneath and straight back.     

  14. Trucks will  run steel, magnesium or aluminum flywheels that meet the following Criteria:

    • Steel plate or steel billet flywheel will have a tensile strength of 60,000 psi and a yield Strength of 40,000 psi. 

    • Magnesium or aluminum flywheels will meet or exceed former SFI standards 1.1

    • No cast iron permitted.

  15. All U-joints must be covered 360 degrees with ⅛” steel or 3/16” aluminum having two (2) Drive shaft hangers per driveshaft ⅛” thick steel or 3/16” aluminum 1 inch wide, six (6) Inches (maximum) above and below shaft.

  16. All drives shafts shorter than 24 inches require one (1) hanger.

  17. Automatic transmissions will have a 4.1 SFI-approved blanket or shield.

  18. BRAKES- all pulling vehicles will have adequate stopping brakes. 

    • 4x4 trucks will have complete working front and/or rear brakes. 

    • All brakes in the driveline will be shielded 360 degrees with 5/16 steel or ⅜” aluminum, Around the brake components. Ends must be enclosed in the ⅛ steel or aluminum, no Cast metal permitted to be used as part of a shield.


    • All engines using a clutch flywheel assembly will run a full block saver plate. Material being ¼ aluminum or 3/16 steel minimum.

    • All automotive type engines using a clutch will use a ¼”, one piece SFI 6.1, 6.2, 6.3 containment bell housing.

    • One cooling hole will be allowed in the bell housing, one (1) inch maximum diameter. Hold must not be in explosion area of bell housing. 

    • No welding will be allowed in the explosion area of the bell housing.

    • No chemical milling permitted

    • There will be five (5) ⅜” bolts or four (4) ½” bolts to secure bellhousing to transmission.

    • All inspection maintenance holes must be no wider than 8 ½” and the ends of the holes shall be smoothly and fully radiused to produce an oval shape.

    • Four (4) ⅜ grade 5 or better bolts are required in the top half of bell housing to block. Six (6) evenly spaced grade 5 or better bolts are required on bottom half of bell housing. 

    • No cast iron clutch components or flywheels will be permitted. 

    • Billet steel, aluminum, SFI 1.1 or SFI 1.3 flywheels will be accepted. 

    • Clutches, flywheels and related components must be mounted to engine on vehicles using automotive type engines.

  20. HITCH:

    • Hitch must be rigid in all directions Hitch length and height cannot change before,during or after pull. 

      • Vehicles with engines greater than 485 cubic inch will lose two inches of hitch height. 

    • All hitch will have an opening minimum of 3.75” x 3”.

    • Point of hook to centerline of rear axle shall be no less than 36% of vehicles wheelbase, however no more than 25 degrees hitch angle. Previous 2015 NK members trucks will be allowed to have it 34% for the 2016 season only. All new 2016 members or trucks are required to follow the 36%.  Hitch height not to exceed 26 inches. Drawbar must be mounted solid to frame.

    • Pulling point can be no more than 1 ½” from back of drawbar.

    • No cable, chain or clevis allowed in hitching device.

    • If bed is too long it may be cut to accommodate 36% drawbar.

    • Hitch point must be clear and visible for hood and unhook of sled chain.


    • See line #15 above.

  22. ENGINES:

    • Shielding on v or y type engines must be from the base of the head to two (2) inches below the crankshaft throw. Frame may be used as all or part of the shield provided it is solid and covers the required area. 

    • All engines will have a deflection shield ,running the complete length of the block casting. Shield must be securely fastened and must be .060 inch thick. Starters, exhausts,fuel pumps,etc., will not be considered as part of the shield.

    • All side shields must be solid. Shielding will be made of a total of .125 aluminum or .090 steel minimum of inch thick.

    • Engine fans must be completely shrouded with steel 1/16”  or thicker. Electric fans excluded.

    • All automotive engines equipped with a harmonic balancer must have balancer that is SFI Spec 18.1 and carry SFI identification.

  23. EXHAUST:

    • No megaphone pipes allowed. Venturis- style headers permitted.

    • No rain caps permitted.


    • The use of torque converters, automatic shifts, etc. will be permitted.

    • All vehicles using an automatic transmission must have an SFI Spec. 29.1 automatic transmission flex plate. No cast iron permitted.

    • All vehicles using an automatic transmission will use a positive gear lockout.

    • All automatic transmissions must have an approved safety blanket over the torque converter area. A full length safety blanket is required. Automatic transmission shield must meet SFI Spec. 4.1.


    • Electronic fuel injection is prohibited 4x4 pro-stock

    • Electronic timing delay devices or programmable ignition boxes prohibited.

    • Ignition control box must be sealed.

  26. SAFETY :

    • Required to use a kill switch

    • Kill switch will be securely mounted to the back of the vehicle and have a two (2) inch diameter ring to attach the sled.

    • A white  safety light is required to indicate that vehicle is in neutral during process of Hooking or unhooking from sled. An additional reverse light, is (recommended), amber in color will Illuminate when vehicle is in reverse.

    • All pulling vehicles are required to have a minimum of 2.5lb. Fire extinguishers which are fully charged and must be within reach of driver. 

    • Seatbelts must require 16.1 SFI spec on all driver restraint assemblies and be worn during competition. 

    • All vehicles will have a safety switch. The safety switch will ground the ignition and the Electric fuel pumps on spark ignition motors

    • No batteries are allowed inside the cab of the vehicle unless they are in a marine battery box and secured to the vehicle frame. Shielding is required for battery posts that are exposed

    • All pulling vehicles will have a dead man throttle that will automatically return to the closed Position.

    • All pulling vehicles must have a starter interrupter switch that will allow starter engagement only in neutral or park position on a transmission gear selector for mechanical reasons during the season.

    • All vehicles using a foot throttle must use a toe strap.

    • All vehicles using an automatic transmission must have a positive gear lockout.

    • Drivers or crew persons must be seated and in control of the pulling vehicle any time motor is started or running.

    • Weights must not interfere with the kill switch or drawbar. An area of 5” wide and 12” high Immediately above the drawbar must be free of obstructions.

    • No stabilizer bars required on 4x4 trucks.

  27. CLOTHING: (adjusted to comply with NK general safety rules)

    • Fire suits (pants and jacket or 1-piece) required, (recommended minimum of SFI 3.2)

    • Fireproof gloves, head sock and shoes meeting SFI Spec,3.3 (recommended)

    • Helmet with strap required. (recommended face shield be worn during competition)

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