IHRA Official Rulebook

Figure 14: Seat mounting

SUPERCHARGERS: ROOTS-TYPE HIGH HELIX: Must adhere to same maximum case dimensions and maximum rotor cavity diameter as standard Roots. Rotor helix angle may not exceed 6.5 degrees per inch (123.5 degrees total over 19” maximum rotor length). Maximum over drive may not exceed 70 percent. Aluminium studs (supercharger to manifold) mandatory. All cases and related components must be accepted prior to competition. See Class Requirements for manifold burst panel and restraint specifications. SUSPENSION: All street driven cars must have a full suspension of the type produced by automobile manufacturers (i.e. springs, torsion bars, air suspension, etc.). Rigid mounting of front or rear axles is prohibited. THROTTLES: Each car, regardless of class, must have a foot throttle incorporating positive acting return springs attached directly to the carburetor throttle arm. A positive stop or override prevention must be used to prevent linkage from passing over center and sticking in an open position. A means of manually returning the throttle to a closed position, by the use of the foot, be installed on any mechanical or altered linkage in addition to return springs. Throttle cables or linkages are permitted in all applications. Licensed hand controls are permitted only with approval from Tech Director. TOW HOOK: All vehicles competing in National or SSNC events, must incorporate a device on the front of the chassis that will facilitate ease in hookup for towing entry from the racing surface. It is recommended that all receiver pins be 1/2” in diameter. TRACTION BARS: All bars must not be longer in overall length than one-half the wheel base of the car. Traction bar may extend into the drivers compartment. TRACTION BAR ROD ENDS: Minimum requirement for rod ends on the front of all ladder type traction bars: .750 steel. It is required that a rod end safety strap be installed to keep ladder bar secured in event of rod end failure. TRANS BRAKE / TWO STEP/ SWITCHES: All vehicles in Super Stock eliminator must have the Trans Brake wire isolated and one color from the solenoid to the button. No quick disconnect is allowed in the system. Trans Brake or switch release must be of traditional mechanical / electrical means. The use of pneumatic or hydraulic switches is prohibited in all classes. Only one release button is acceptable for the system. TRANSMISSION SHIELD OR BLANKET: See class requirements. SFI Spec. 4.1 mandatory. TRANSMISSION: Any non-automotive-production transmissions must comply with IHRA Safety Specs. Automated shifting of manual transmissions prohibited in SS and Stock. Each shift must be a direct function of the driver. All automatic transmissions must have reverse lockout and a working neutral start safety switch . TWO-WAY RADIO COMMUNICATION: The use of two-way radio communication is permitted in some classes, see specific class requirements for details. Telemetry function prohibited. All on board radios must be securely mounted with a positive retention device. VENT TUBES: (BREATHERS) All tubes must vent into frame or chassis or IHRA approved expansion tank. Positive locking crank case breathers are mandatory on all entries running 7.99 or quicker 1/4 or 5.49 or quicker 1/8 mile. See class requirements. WHEEL BASE: On cars required to maintain stock O.E.M. wheel base, a 3/4” allowance for wheel alignment will be allowed. However, left to right variation cannot exceed one inch. WHEELS & TIRES: Hubcaps must be removed for inspectors, who will check for loose lugs, cracked wheels, worn or oversize lug holes, spindles, axle nuts, cotter pins, etc. Snap on hubcaps or tie wrap wheel covers are not permitted on any class car during competition. Tires will be visually checked for condition, pressure, and must be considered safe by the Technical Committee prior to any runs by the car. Recapped tires are prohibited. All street tires must have a minimum of 1/16” tread depth. Each car in



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