Tech Information

Effective Immediately 3/16/2023

1. GN Light Modified division weight limit is now 6200 lbs. for 2023 season.

2. Super Farm, Light Pro Stock, and Limited Pro Stock divisions cannot enter the new RN Heavy Pro Stock 5.0 class. Entering of stated vehicles in divisions other than RN Heavy Pro Stock 5.0 as permitted by 2023 NTPA Pulling rules is still allowed.

3. The WPI Executive Board moved to limit Mini division at all levels to any current 18.4×16.1 – 6 ply tires already in competition from 2022 season (Pioneer, Cepek, Mayhill). No changes to construction or dimensions of these tires will be allowed for the 2023 season. Limiting Mini division to these tires will maintain current vehicle dimensions and weight limit while keeping competition at an already high level.

Correction to rules for the 2023 rulebook

Page 75 at top under both 1) and 2)

the letter d) rule should be deleted.

  • d) Rotors must be contained within a one-piece rotor case.

Light Limited Super Stock subsections

1. Engine

  • o) Maximum of 470 cid. for single turbocharged diesel engines.
    • 3.This engine combination can run a maximum of one (1) 3.4X4-inch smooth bore turbo OR (1) 3×4 turbo with maximum of .200-inch MAF enhancement ring, no forward facing MAF.
  • p) Maximum of 370 cid. for single turbocharged alcohol engines.
    • 1. No intercoolers allowed.
    • 2. This engine combination can run a maximum of one (1) 3X4 smooth bore turbocharger.

2. Turocharger Restrictions

  • a) All turbo compressor and exhaust wheels must protrude into the housing restricted opening no less than 1/8-inch.
  • b) Engines limited to a 3×4-inch turbo, the 3-inch compressor wheel must protrude into the housing 1/8-inch and compressor wheel must measure no larger than 3 inches at face of wheel.
  • c) Diesel engines limited to a 3.4X4-inch smooth bore turbo, the compressor wheel must protrude into the housing 1/8-inch and the compressor wheel must measure no larger than 3.400-inches at face of the wheel.
  • d) No superchargers allowed.

Attention Competitors with a Modified Mini

It has come to the attention of NTPA Technical Services that certain variations in construction of the SFI 47.3 rollcage do not meet standards set forth by SFI or do not meet NTPA roll cage mounting guidelines. The SFI 47.3 standard for vehicles that compete at 2,000 lbs., namely Modified Mini division, has been in place since 1998 and the specifications for construction and mounting of the rollcage have never changed.

Therefore, the WPI Board of Directors has determined the following corrective action is necessary.

  1.        All 47.3 rollcages must have a diagonal bar installed between the front and rear vertical tube on each side of the rollcage as specified. This tube may currently be installed in the horizontal position and will need to be removed and a new tube fitted diagonally in the correct location according to the SFI specifications.
  2.        NTPA rollcage mounting standards for both tube type or channel type chassis require a 1/4-inch x 3-inch steel web plate be properly welded at base of rollcage on each side between front and rear vertical tubes as well as across the rear of the rollcage. The flat, 1/4-inch x 3-inch steel plate needs to be installed between each vertical tube all the way around the rollcage, connecting all vertical tubes together.

Any SFI 47.3 rollcage that is in violation of the issues described will have until June 01, 2023 to complete the repairs in order to compete during the 2023 season. Once the roll cage has been updated to meet the requirements described, the rollcage will be re-certified by a NTPA Rollcage Inspector at no charge to owner and a new 5-year certification sticker will be installed.

NTPA Technical Services recommends that competitors contact their chassis / rollcage manufacturer for more details regarding any corrective action necessary. A copy of any SFI standard can be obtained by contacting SFI directly at 858-451-8868 or follow the following link to order,
A copy of NTPA Rollcage Mounting Standards can be obtained by contacting NTPA Technical Services.

Marvin Epperson
NTPA Director of Technical Services

For more information and pictures of acceptable ways to fix the diagonal bracing, visit the NTPA’s tech page using this link:

Items/rule changes that go into effect for the 2023 season

General rules:


Rule a. replaced with: Bellhousing must be mounted as SFI certified by manufacturer with grade 8 studs or bolts that can be identified as grade 8. Socket head bolts allowed only for clearance problems.

Rules e and f. replaced with: Bellhousing must be mounted with grade 8 studs or bolts per manufacturer’s bolt pattern for motor and bellhousing. All bolts must be in place.

Rule i updated: Starting Jan 1, 2024 all SFI bellhousings regardless of material i.e. steel, titanium or aluminum must display a current SFI sticker with an expiration date affixed by the manufacture. The NTPA steel stamp will no longer be acceptable as a replacement for SFI decal after Jan 1, 2024.


Exhaust rule 7, pg. 33 and 34 – added Or, a billet steel cross/cage incorporated into the exhaust outlet supplied by the turbocharger manufacture. (Dimensions still in process)

Injection Pumps

     P7100 Series Pump:  For classes limited to maximum size injection pump of P7100 series, pump housing (main pump body) dimensions not to exceed 2-5/8” wide X 9-9/16” long X 8-3/16” tall. Limit one plunger per cylinder. No billet pump housings. Pump will be held to OEM centerline of fuel rack to top of housing and centerline of camshaft to top of housing and OEM plunger bore centerline.

     Divisions limited to P7100 injection pump are: Light Pro Stock, Limited Pro Stock, Pro Farm, and Light Limited Super Stock.

     P8600 Series Pump:  For classes limited to maximum size injection pump of a P8600 series, pump housing (main pump body) dimensions not to exceed 3.175” wide X 10.475” long X 8.665” tall (+ or – .010”). Limit one plunger per cylinder. No billet pump housings.

     Divisions limited to P8600 injection pump are: Super Farm and Hot Farm.

     Injection pump required to be mounted in the stock location only in affect for Light Pro Stock Tractors which is no change to previous class rules.

  Diesel Fuel

     All diesel fuel and diesel / bio blends will be measured using a dielectric meter only. A maximum reading of 13.4 / 150 based on which type of dielectric meter used.

Water Injection

    Water and soluable oil (lubricant) mixture must measure plus or minus .2 using a water hydrometer or a maximum reading of 5 on a refractometer.

Modified Tractors

Light Unlimited deleted. Light Modified adopted and offered at SN/GN level.

Light Modified

Limited to two supercharged automotive type piston engines limited to 14/71 size supercharger with no overdrive limit, or may be turbocharged. No single engine tractors, no naturally aspirated engines or turbines. Weight limit is 6,000 lbs.

Mini Rod:

Maximum weight will remain 2050 lbs. Vehicle no longer required to have any moveable weight.

Contest Operations

“New” Sled Bump Rule

a. Any competitor who breaks at the event site will receive hook points for all classes entered, but will not receive place points or any purse money unless there has been a measurable pull by that vehicle in that respective class except under circumstances covered in letter b.

b. Competitor is not required to bump sled if breakage occurs during first session of competition and not able to compete in second session for same class only. Place points issued only in class with 15 or less total entries including per hook, non-member entries. Rule does not apply if vehicle has not competed in first session of class that breakage occurred. Vehicle must make a measureable hook in first session in order to qualify for last place points in second session of same class. If vehicle has already competed and recorded a measureable distance in a different class previous to breakage and is entered in that same class in a later session, then vehicle will be awarded place points under same conditions in both classes.
Example: vehicle competes in UNL in session 1 making a measureable distance and then breaks during competition in MOD class in session 2. If vehicle is unable to compete further in that event, then vehicle would qualify for last place points in second session for both classes under criteria described previous.

Contest Procedures

First Pull Attempt

a. On first attempt, no matter where the vehicle stops prior to 100 foot, as long as competitor lets off the throttle prior to 100 ft. marker, no matter the circumstance causing (out of bounds, kill switch pulled, lost weight, roll over, etc.), competitor will get a second attempt. Even if vehicle travels beyond the 100 ft. marker, competitor will be allowed a second attempt as long as competitor let off the throttle prior to 100 ft. marker.

b. If no attempt is made to let off the throttle, no second attempt will be granted.
Note:  Intent is for driver not to slam on brakes to stop before 100 ft. marker (or at any time), but to come to a smooth, safe stop.

c.  All competitors, except “Test Puller”, will have the option to make a second attempt immediately or drop (6) positions after first attempt as long as competitor did not go past 100 feet. Competitor will have one attempt remaining. For “Test Puller” options, see Section…….

Additional classes

Pro Stock Tractors – RN level on trial basis in Region 2

     Turbo limited to 5 inch intake and exhaust, no intercooler, all other rules for Pro Stock class in NTPA Rule Book remain the same as GN Heavy Pro Stock including cubic inch, component chassis and weight.

Super Stock FWD Trucks:

(this class will move from the back of the book to the front and be a regular RN class)

1. Super Stock FWD truck shall follow the NTPA Rulebook for Modified Four Wheel Drive except where superseded by rules found therein.

2. Maximum wheelbase of 133 inches for Super Stock FWD trucks. Must have OEM frame of a truck. All rear end housings must be fastened rigid to the frame. Front axle must be a Dana 70 or under automotive front.

3. Engine to remain in stock location as intended by manufacturer plus or minus 3 inches. Mini Truck (S-10, Ranger, Dakota, etc.) are permitted to run V-8 engines.

4. Front axle must remain in intended original location. Center of front or rear wheels cannot exceed plus or minus 2 inches of fender walls being used.

5. Engine must be the same manufacturer as the truck. Center to center bore spacing to be OEM stock on the engine (Ford 4.9, GM 4.84, and Mopar 4.8). Any cam allowed, and intake manifold changed permitted with one single, four-barrel carburetor with working floats and mechanical linkage. Not to exceed standard 4500 series dominator gasket. Engine must run on gasoline fuel only. Aluminum heads are permitted. No hemi or semi hemi style head. Heads must be cast and not billet. Fuel injection and/or air compressing devices are not permitted.

6. Engine block must be OEM stock steel or its replica, no aluminum engine blocks permitted.

7. Fuel samples and or fuel tests may be conducted at any time at the discretion of the competition director.

8. Hitches to be built to specifications in NTPA Modified FWD section. Hitch length to be a minimum of 30% of the wheelbase.

9. Maximum tire size is 35 inches tall by 12.5 inches wide or metric equivalent of 315/75. Must be a D.O.T. tire.

10. Can use aftermarket transmission and transfer case.

11. Any type of rear end may be used. (Military and or 2 ½ ton truck or automotive)

Note:   Region 2 is limited to 410 cubic inches

            Region 3 is limited to 530 cubic inches

            Region 6 is limited to 500 cubic inches

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