Tech Services

2026 NTPA Pulling Rules – Release Update 12-09-2025

7,500 lb. GN Modified

1. Engine Combinations

b) Three blown automotive engines equipped with 18-71 superchargers at 70% maximum overdrive or PSI screw-type superchargers limited to C or D rotor only at 94% maximum overdrive

High Pressure Common Rail Fuel System – Safety Shutdown

1. All pulling vehicles with engines equipped with High Pressure Common Rail Fuel Systems (HPCR) are required to incorporate a manual switch that can be operated by track officials that will disconnect battery supply to the engine ECU which controls fuel injection. The main battery disconnect can be used for this purpose if switch is labeled and located in the required position.
2. Pro Street Diesel 2.6 4X4 Trucks, Pro Stock and Super Stock Diesel 4X4 Trucks
   1. HPCR disconnect switch must be located at left end of the front weight box or weight rack. Switch must be easily accessible and identifiable.
3. Semi
   1. HPCR disconnect switch required to be located at left end of bumper. Switch must be easily accessible and identifiable.
4. This rule does not eliminate the required 3-way fuel bypass valve located in fuel supply system before the high pressure pump. Refer to F. General Rules – section 19. Safety – sub-section k. Fuel Shut-off / Diesel Bypass Valve for more details.

Intercooler Containment

1. All remote mounted intercoolers (ie. intercoolers not direct mounted to the engine within the engine shielding) must be securely fastened to the chassis or to a structure that is mounted directly to the chassis. Intercooler cannot be suspended by the air inlet or outlet pipes.
2. Intercooler cannot be mounted behind the vehicle firewall within the driver’s compartment.
3. Intercooler housings made from a billet material will be required beginning 2027 NTPA season in Heavy Pro Stock, Super Stock Diesel 4X4 Trucks, and Semi divisions. No welded housings will be accepted after end of 2026 season.
4. All intercoolers not contained within the normal engine shielding must be shielded the same as a turbocharger not under the hood. Refer to F. General Rules – section 22. Shielding – sub-section g. Intercooler Shielding for more details.

GN 4.1 Pro Stock

• 4.1 Pro Stock at GN level are limited to competing in their own division.

TWD Tires (all levels) – effective 2027 season

1. Maximum tire size limited to 143-inch circumference out of the mold and 19.5-inch tread width after cutting, mounted on rim, and in ready to compete condition.
2. Tires in competition will be measured and monitored during 2026 season to support any change necessary to these specs.

Pro Street 2.6 4X4 Trucks

• Use of non-OEM, aftermarket driveline components are accepted in Region 3 only

Pro Charger (centrifugal supercharger)

• Pro Charger (belt driven, centrifugal supercharger) is not accepted in any division of NTPA competition

Modified Mini

• Turbine engines are not accepted in the Modified Mini division at any level of NTPA competition

Limited Modified Rules – RN Level
Proposed for 2027 Season

1. All Modified tractor overall general and safety rules apply.
2. Maximum weight is 6500 lbs.
3. One blown automotive engine with maximum 14-71 supercharger
   1. Maximum 2 valves per cylinder, one spark plug per cylinder, limited to 575 CID
4. One Allison engine
   1. Maximum of 9.6 to 1 supercharger ratio with stock Allison 9.5-inch blower wheel.
   2. Must use SFI spec 4.2 blower containment device.
5. One Packard V12
   1. Maximum 6.5 to 1 supercharger ratio
   2. Stock Packard butterfly must be utilized.
6. Any combination of N/A automotive style engines with a combined displacement of 1,400 CID
7. Any combination of forced induction, wedge head, automotive style engine with combined displacement of 750 CI, no billet blocks or heads allowed.
   1. Turbochargers limited to one per bank, non-staged.  76mm inducer compressor side, 76mm exducer turbine side.
   2. Engine driven blowers allowed are centrifugal and roots. Maximum limit of (2) 8-71 roots blowers.
   3. No screw type blowers
   4. No intercoolers
8. One Ag or Industrial style engine limited to 505 CID displacement on alcohol
   1. Aftermarket aluminum heads allowed no overhead cams allowed
   2. Turbo is limited to 4.1” smooth bore inlet opening with maximum 4.5-inch exhaust wheel, intake and exhaust wheel must protrude 1/8-inch into housing
   3. No MAP width ring enhancement
9. Single Diesel Engine – maximum 540 CID
   1. Turbocharger limited to 4.8-inch intake opening – MAP width ring opening accepted
   2. Intake and exhaust wheel must protrude 1/8-inch into housing
   3. No intercoolers
   4. All LT Pro engine rules apply
10. Single Diesel Engine – maximum 640 CID
    1. Turbocharger limited to 4.1-inch smooth bore intake opening
    2. Intake and exhaust wheel must protrude 1/8-inch into housing
    3. No intercoolers
    4. All other 4.1 PS engine rules apply
11. Any combination of automotive style diesel engines, I.e. Duramax, Cummins, and Powerstroke
    1. Engine(s) limited to combined 900 CID maximum displacement.
    2. Limited to one turbocharger per engine with maximum 76 mm inducer compressor side and 88 mm exducer turbine side
    3. Intake and exhaust wheel must protrude 1/8-inch into housing
    4. No intercoolers
12. Turbine horsepower maximum military rating of 2,300 hp. single or any combination accepted. All turbines must be inspected annually by NTPA Technical Services and operated within military specifications. Average additional horsepower is 10% for water and 10% for methanol
    1. One Lycoming T53 L-13 turbine rated at 1400hp military spec – water and alcohol injection accepted
    2. Twin Lycoming T53 L-1, L-11 – water and alcohol injection accepted
    3. One Lycoming T55-L5 turbine rated at 2200hp military spec. Must be sealed at authorized repair shop. No alcohol or water injection accepted
13. One 1,100 CID Ford GAA Engine on alcohol
    1. Limited to two, non-staged turbochargers, one per bank
    2. Maximum 88mm inducer on compressor side and 99mm exducer on turbine side
    3. Intake and exhaust wheels must protrude 1/8-inch into housing.