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Throwdown in T-Town Legal Pro Mod Rules

FIELD: 8 car qualified field.

MINIMUM WEIGHT: 2300 pounds for naturally aspirated entries, 2425 pounds for Nitrous entries, 2600 pounds for Supercharged entries and 2650 pounds for Turbocharged entries.

MAXIMUM CUBIC INCH ENGINE DISPLACEMENT: 526 cubic inch maximum for roots style supercharged cars, 650 for centrifugal supercharger. 540 cubic inch maximum for Turbocharged entries and unlimited cubic inches for Nitrous powered and naturally aspirated entries.

BODY: Funny car or one piece bodies not allowed even if equipped with doors. Maximum front end overhang of 45” as measured from centerline of front spindles. An extension may be used to create 45” overhang if the front end overhang of the original body is less than 45”. All bodies must originate from a documented production vehicle.

DOORS: Required. Doors must be functional and able to be opened from both the inside and outside of the vehicle. Doors may be fabricated from carbon fiber, fiberglass or metal. A metal deflector between the fenders and the leading edge of the doors is required.

FIREWALL: All firewalls must be made of 0.024 thick metal or thicker. Composite not allowed.

TAIL LIGHT: Functional rear tail light is required. Minimum of 1 tail light is required to be operational and controlled from the drivers compartment.

BALLAST: Permitted. All weight bars, pucks, etc. must use minimum 1/2 inch-diameter SAE Grade 8 bolts for attachment. Weight bags filled with lead shot or similar are prohibited.

CHASSIS: Must be SFI Spec. for your vehicles E.T. and Speed based on NHRA requirements.

GROUND CLEARANCE: Minimum of 3” required from front of car to 12” behind front axle centerline, 2” minimum for remainder of car.

STEERING: Stock type steering in conventional location required. Disconnect meeting SFI Spec. 42.1.

SUSPENSION: Race car type suspension required. Solid suspension prohibited. Shock absorbers required for all four wheels. Lockup shocks prohibited. Active suspension of any kind prohibited. Any ability to make on-track setting/rate changes based on “real time” data or input from any source is prohibited. Electrically or pneumatically controlled, hydraulic shocks and/or struts are permitted, provided all adjustment settings/changes are preset before the run. Only 1 three-wire shielded cable connection is permitted from the top of the shock/strut to the shock/strut controller. Electrical connections of any other kind to or from the shock/strut prohibited. Shock/strut travel sensors permitted, but may ONLY be connected to the vehicle data recorder. Shock/strut control boxes that have connections for travel sensors must have the pin removed from the connector. Connection to serial port on control box prohibited once car reaches the ready line. All wiring must be visible and easily traceable.

TIRES: Slicks permitted. Must be automotive type tires designed specifically for racing. Tires cannot be located outside of bodyline. All tires must have manufacturer, model and or part number and size information must be clearly and permanently designated on sidewall.

WHEEL BASE: Maximum 115″. S-10, Ranger, Dakota Maximum 125″. Full size trucks Maximum 140”. Maximum variation is 2” side to side.

WHEELS: Maximum rear wheel width 16” measured between the inner and outer tire mounting surfaces.

CLUTCH/FLYWHEEL: Throwout bearing must release all fingers, levers, stages, etc. simultaneously. Staged or variable release clutches of any description prohibited.

ENGINE: Internal-combustion, reciprocating, single-camshaft, 90-degree V-8 automotive-type engine. Bore Spacing is set to a MAXIMUM of 5.300” for Nitrous or Naturally aspirated Cars, 5.000” for turbo cars, 4.900” for Billet Hemi head supercharged vehicles and 5.000” for all other supercharged combinations.

DRIVELINE: A full 360 degree drive shaft tube is required over yoke, extended a minimum of 9” required from transmission tail shaft. Minimum thickness of tube housing is .050” chrome-moly or titanium. Two piece units accepted with a minimum of 6 attachment points using 3/8” grade 8 bolts.

ENGINE CONTAINMENT SYSTEM: SFI Spec. 7.1 or 7.2 lower engine containment system required.

FUEL: The use of nitromethane and/or propylene oxide is strictly prohibited.

FUEL SYSTEM: Fuel cell must have pressure cap and be vented to outside of body. Fuel cell meeting SFI Spec 28.1 mounted in front of radiator permitted; must be mounted between framerails and enclosed in a round tube frame, minimum 1 1/4” O.D. x .065” chrome-moly tubing. Extra tank(s) prohibited. Artificial cooling or heating systems (i.e., cool cans, ice, Freon, etc.) prohibited. Circulating systems, not part of normal fuel-pump system, prohibited. Water injection permitted on Nitrous entries only, only water permitted in water injection system.

IGNITION: Maximum one magneto or distributor, maximum one spark plug per cylinder. Magneto systems are limited to a single 44-amp maximum output system.

INTAKE MANIFOLD: A burst panel is required on all vehicles if they have a power adder.

NITROUS OXIDE: Prohibited on Turbo and Supercharged entries. Maximum of two bottles stamped with a DOT-1800 pound minimum rating.

REAR END: Maximum numeric rear-end gear ratio 4.57-to-1 for supercharged and turbocharged entries.

STARTER: Required. All entries must be self-starting. On board starter required. The use of remote-mounted battery packs permitted for starting purposes only. Remote battery may not be used for starting after the burnout has been started. No push starts allowed.

SUPERCHARGER: Screw-type supercharger prohibited. Hi-helix or standard helix Roots type supercharger only. Maximum roots style supercharger overdrive limit is 14.55 percent. Roots Type: Maximum size: 14-71. Rotor helix angle may not exceed 6.5 degrees per inch (123.5 degrees total over 19” maximum rotor length). Maximum of one 140 mm opening for Centrifugal superchargers.

TURBOCHARGER: Twin turbochargers limited to 88mm. Turbocharger size will be verified by measuring the housing bore at the leading edge of the impeller wheel. The maximum diameter of the housing bore at the leading edge of the wheel may not exceed 2mm more than the maximum allowable turbocharger size permitted.

TRANSMISSION: Supercharged entries limited to maximum of three forward speeds and reverse; all other entries limited to maximum of five forward speeds and reverse. Lockup converters and overdrive units are prohibited. A 1-to-1 relationship is mandatory in high gear for all transmission types.

CREDENTIALS: A NHRA Competition License for your ET is required to compete.

SAFETY EQUIPMENT DRIVER RESTRAINT SYSTEM: SFI Spec. 16.1 certification required.

FIRE SYSTEM: SFI Spec. 17.1 system required. System must contain a minimum of 5 lbs of fluid or gas fire suppression agent. 20 lbs systems are recommended on all entries with power adders. One nozzle required inside driver’s compartment must be directed at driver’s feet. Two or more nozzles must be directed at front of engine and fuel cell. All fire suppression must be released with a single actuation. (i.e. single handle, button or lever)

HEAD AND NECK RESTRAINT: SFI Spec. 38.1 required.

HELMET: SN-2005 or newer of SFI Spec. 31.2 or 41.2 required. Use of open face helmet prohibited. EjectHelmet Removal System (Part # SDR 890-01-30) or equivalent recommended

MASTER ELECTRICAL CUTOFF: Required. Must be clearly labeled “PUSH OFF”.

PARACHUTES: Dual parachutes required. Separate shroud-line mounting points with 1/2” sleeved grade 8 bolts required.

PROTECTIVE CLOTHING: A driver’s suit meeting SFI Spec. 3.2A/15, gloves meeting SFI Spec. 3.3/15, shoes meeting SFI Spec. 3.3/15 required for Nitrous entries. A driver’s suit meeting SFI Spec. 3.2A/5, gloves meeting SFI Spec. 3.3/5, shoes meeting SFI Spec. 3.3/5 required for naturally aspirated entries. A driver’s suit meeting SFI Spec. 3.2A/20, gloves meeting SFI 3.3/20, shoes meeting SFI Spec. 3.3/20 required for Supercharged and Methanol burning Turbocharged entries. A head sock meeting SFI Spec. 3.3 is required unless a helmet manufactured with a skirt meeting SFI Spec. 3.3 is used.

ROLL BAR PADDING: Required.

WINDOW NET: SFI Spec.27.1 required.