Tech Information

Items/rule changes that go into effect for the 2021 season

Attention NTPA Competitors: The following items were considered and approved by the WPI/NTPA Executive Boards for the 2021 season.

  1. Heavy Super Stock Diesel GN/SN: Limited to a maximum 540 for all turbocharger configurations.
  2. Open Super Stock: The following rules have been added to current rules.
    1. Maximum 650
    2. Inline or V configuration engines only.
    3. OEM block or aftermarket replica must be from an agricultural machine application.
    4. Engine brand not required to match brand of sheet metal used.
  3. Light Limited Super Stock: Adopted as an NTPA sanctioned class for regional national competition.

Light Limited Super Stock Rules: All OEM chassis Pro Stock rules, including shielding, safety and SFI requirements, apply to this class plus the following rules:

  • Weight

    1. Tractor weight will be 6,250 lbs.
  • Engine
    1. Engine must match brand of tractor. Engine crankcase, block, and cylinder head must be of same manufacturer or factory replacement and can be used in any agricultural transmission and rear end that used that brand of engine or through its company mergers used that brand of engine.
    2. Must be OEM engine block, no Billet steel or aluminum blocks.
    3. Rear of engine must be in stock location for make and model of rear end and transmission housing, with a maximum tolerance of a 1” adapter plate.
    4. No V-8 Engines permitted.
    5. No Overhead cams allowed.
    6. Maximum allowed “P” pump. Only one plunger per cylinder allowed.
    7. No electronically controlled fuel system allowed.
    8. No secondary source of fuel (liquid or gas) or oxygen enhancer allowed.
    9. Water injection allowed.
    10. Computer can only be used for data acquisition, may not be able to control engine timing, or fuel delivery. No traction control.
    11. Maximum of 315 cubic inches for twin turbocharged diesel engines with Intercoolers. (Turbo(s) must be staged.) This engine combination can run a maximum of two (2) 3 x 4 smooth bore turbo(s). No MAF enhancement.
    12. Maximum of 360 cubic inches for twin turbocharged diesel engines and no intercooler or after cooler allowed. (Turbo(s) must be staged.) This engine combination can run a maximum of two (2) 3 x 4 smooth bore turbo(s). No MAF enhancement.
    13. Maximum of 410 cubic inches for single turbocharged diesel engines. Intercoolers allowed. This engine combination can run a maximum of one (1) 3 x 4 turbo with MAF enhancement. 0.200 MAF enhancements. No forward-facing MAF.
    14. Maximum of 470 cubic inches for single turbocharged diesel engines. No intercoolers allowed. (The 478 cu. in. Hercules engine will be legal to run in its factory combination 0% variance on CID.) This engine combination can run a maximum of one (1) 3.4 x 4 smooth bore turbo.
    15. Alcohol Engine maximum of 370 cubic inches for single turbo charged alcohol engines. No intercoolers allowed. This engine combination can run a maximum of one (1) smooth bore 3 x 4 turbo.
  • Turbo Restrictions

    1. Diesel engines that will be allowed to run a 3.4 x 4 smooth bore turbo, the compressor wheel must protrude into the housing 1/8″ and the compressor wheel must measure no larger then 3.400” at the face of the wheel.
    2. No superchargers allowed.
  • Cylinder Heads
    1. One spark plug per cylinder ONLY.
    2. Maximum of 2 valves per cylinder. Valves must maintain the factory angle, lateral movement of valves only. Valves must seat in the bottom of the OEM head on all 6-cylinder engines.
    3. OEM cylinder head for that brand and model engine. No billet or re-cast cylinder heads allowed.
    4. Maximum of one (1) deck plate will be permitted between the top of the block and the bottom of the cylinder head, with a maximum thickness of 1-1/8″.
  • Chassis
    1. Maximum length 13 feet measured from center of rear axle to forward most point, excluding tow hook. Maximum wheelbase 114”.
    2. No type of front end suspension allowed, swivel axle front ends will be accepted.
    3. All housings must stay in place, bolted ridged in all other chassis.
    4. Auxiliary transmission will be permitted.
  • Tires
    1. Maximum tire size 30.5 x 32, Minimum tire size 24.5 x 32.

General Rules:

  • Safety – Turbochargers – all divisions
    1. Intake Compressor Wheels – No turbocharger compressor wheel(s) may be visible through hood or side shield on either side of vehicle. Any visible inlet compressor opening must face forward.
    2. Exhaust Turbine Outlet – 2 bolts, minimum 1/2” diameter, grade 5 only, must be installed in a cross pattern as close to turbine exhaust wheel as possible.
    3. Turbocharger Containment
      • Note: This rule only applies to turbocharger(s) with larger than 3″ diameter inlet
      1. Diesel Engines:
        • Any single turbocharger or top turbocharger(s) on a multi turbo setup must have a Kevlar lined containment device (bag or blanket) that completely encloses the intake compressor housing. Bag or blanket used must be commercially available from a NTPA approved manufacturer.
          • Note: Containment device cannot be homemade.
      2. Alcohol Engines:
        • Any single turbo or the top turbocharger(s) on a multi-turbo setup must have a minimum of 1/8” cable wrapped around turbo. Cable must be wrapped at least two revolutions capturing both turbocharger housings. Cable must be clamped by a minimum of two clamps at splice or metal collars around intake housing with attaching 1/8” cables to exhaust housing. Turbocharger containment device (bag or blanket) is an acceptable option in place of cable if applied as required under diesel engine turbo blanket or bag rules.

Rule Clarification: The rule pertaining to the containment device on a multi turbo diesel truck or tractor has been changed to read:

  • Turbocharger Containment
    • Note: This rule only applies to turbocharger(s) with larger than 3 inch diameter inlet
    1. Diesel Engines: Any single turbocharger or the turbocharger mounted directly to exhaust manifold on a multi turbo setup must have a Kevlar lined containment device (bag or blanket) that completely encloses the intake compressor housing. Bag or blanket used must be commercially available from a NTPA approved manufacturer.
      • Note: Containment device cannot be homemade.

Items/rule changes that went into effect for the 2020 season

Attention all pullers: Note the following clarifications/updated wording to General Rules (2020 Pulling Rules, page 23) effective immediately:

Rule 4 now reads:

4. The following rule will apply to all divisions that use solid driveline shields over 16 inches in length:

  • Note: this also applies to Mini Rod division and the intermediate shaft on FWD.

All driveline shield components must be tethered on each end by two opposing restraints. Tethers must attach at 180 degrees of each other and a minimum of 3” and a maximum of 6” from each end of each driveline shield component.

Tether to be constructed of a minimum of 2” wide by 1/8” thick nylon or polyester strap. One end of tether must attach to one side of the chassis, then go around the driveline shield, then attach to the other side of the chassis. Tether must be attached to chassis by a minimum of one 3/8” grade 5 bolt with a grommet on each side or wrap around the chassis and use a buckle to fasten it to itself.

  • Note: FWD drivelines that use driveshaft hoops must use same tether configuration to be attached to main or common hoop holder between chassis and hoop assembly.

Attention: Competitors in Turbocharged Divisions/Pro Stock: The following rules are effective immediately:

  1. Titanium compressor or exhaust wheels are not allowed in any/all NTPA classes that use turbos at all levels of competition.
  2. Heavy Pro Stock tractors are limited to the following:
    • Exhaust limited to 6-inch diameter exhaust to be measured at the face of the wheel.
    • Exhaust wheel must protrude into the 6-inch bore by 0.125” minimum.
    • All exhaust must exit the 6-inch bore.

General rules:

  1. 2019 rulebook pg 18, letter C, number 12 b, now reads:
    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 1/4-inch aluminum with (6) 3/8-inch Grade #5 bolts evenly spaced on the bottom of the bellhousing. Bellhousing must be fastened with a minimum 3/8″ grade #5 bolt installed in each bellhousing mounting hole as manufactured. All bellhousing mounting bolts must pass through block plate or at least fasten block plate to bellhousing.”
  2. 2019 rulebook pg 24, letter G now reads:
    Automotive engine is any engine or its replica available in a passenger car. Maximum of (8) cylinders. Maximum supercharger size: 14-71, 19-inch rotor case length, 11.25-inch rotor case width. Helix restricted to a maximum rotor spiral of 6.5 degrees per inch of rotor length. Variable multi-speed supercharger devices prohibited.”
  3. Add to 2019 rulebook pg 41, letter R:
    Pro Charger allowed in all divisions with a limit of 140 mm inlet, at 45% overdrive maximum.
  4. Add to 2019 rulebook pg 25, letter G, number 5 and pg 41, letter R:
    “Screw-type superchargers are only allowed in the Unlimited (light and heavy) class. Overdrive limited to 125%.”

Mini Rods:

  1. 2019 rulebook pg 60, letter A, number 1 now reads:
    Automotive engine or its replica available in a passenger car limited to a maximum of 575 cubic inches blown with a maximum 4.900-inch centerline bore spacing or 650 cu. in. naturally aspirated or one gas turbine with an 1,800-hp limit for all National levels of pulling.
  2. Add to 2019 rulebook pg 63 new letter J to read:
    At Super National events in Mini Rod division, no vehicles equipped with small block (blown or otherwise) or naturally aspirated engines (regardless of size) or with rear tires smaller than 18.4 x 16.1 are allowed to enter and run.”

TWD Trucks

  1. Add to 2019 rulebook pg 76, letter F, number 3, new letter b:
    Prior to competition, a TWD must be equipped with an NTPA-approved assembly that will accept a wire tie-type adjustment lock seal. This seal will be applied and secured at the time of drawbar measurement and inspection. The system must be designed so that the seal prevents the drawbar from further adjustment in any direction. (details and drawing will be in 2020 rulebook)

Contest Operations:

  1. 2019 rulebook pg 88, letter E number 7 now reads:
    If a session is cancelled more than 24 hours prior to start time at GN/SN or 3 hours at RN/state level, no points will be given for that session.”


2019 Rule pg 87 letter D, number 1 & 2 now reads:

  1. At all NTPA-sanctioned events, (all levels) the maximum measurable distance will be 350 feet. Length/distance may be less as determined by that event’s insurance application and as verified by NTPA.
  2. The boundary lines at all levels will extend to 350 feet.”

Rules and Regulations:

Are you a puller? Or just thinking about becoming one? Or maybe you’re a fan and want to know the nuts and bolts of this pulling thing. Whatever your need, the latest Official NTPA Rulebook has all the answers about what’s legal and what’s not. It also explains event operations and the NTPA points system.

Click here to order your copy of the NTPA Rulebook from our online store!

You can also call the NTPA office at 614-436-1761 or mail $6.00 plus $2.00 shipping and handling to WPI/NTPA, 6155-B Huntley Rd. Columbus, OH 43229.

Head Tech Official
Roger Kutz
(262) 473-2531

Attention NTPA Competitors, Officials, and Fans: 2021 NTPA Pulling Rules Addendum
The 2021 NTPA Pulling Rules Addendum lists all new and revised rules that have been approved and implemented since the printing of the 2020 rulebook. Members will receive this document in their February membership mailing with their other materials. The 2021 Addendum will also be included with 2020 rulebooks purchased from