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Thumper Rules 2014   (10/01/13)

 No transmitting or listening devices in car except race receivers which ARE MANDATORY!! No exceptions! ZERO TOLERANCE!! NON WORKING OR LISTENING DQ!!!         

A.  Car & Body

1.  No convertibles, compact cars or trucks.

2.  Firewalls may be custom made with steel

3.  Firewalls may be moved back.

4.  Front fenders must remain at least 75% of original size

5.  Bumper type is optional

6.  Three (3) windshield bars in front of driver mandatory

7.  No mirrors

8.  Mandatory front & rear hook-up loops to assist wreckers

9.  Numbers must be on both doors and top of car

10.  Numbers must be at least 4” thick and 20” high

11.  One (1) or two (2) digit numbers and no more than one (1) letter

12. Factory production complete full parallel American passenger car frame only

13. NO engineered or tube type front clip allowed.

14. Must be full and complete on both sides.

15. No part of the frame may be lower than four (4) inches from the ground                                                                                     except front cross member.

16.  If frame or chassis is fabricated from rear kick up to rear of car add 200lbs with 100 of those pounds in front of ball joints.


B.  Roll Bars

1.  Car builders and driver/owners are responsible for roll bar installation.

2.  Round steel tubing, seamless roll-over bars are required for the basic roll cage.  Acceptable minimum size tubing is as follows: one and three-quarters (1 ¾) inches by 0.090 of an inch or one and one-half (1 ½) inches by 0.095 of an inch for mild steel and DOM tubing - one and three-quarters (1 ¾) inches by 0.083 of an inch for chrome-moly tubing).  Aluminum and/or other soft metals are not allowed.  Roll bar connections must be properly welded.  Roll bar installation and workmanship must be acceptable to track officials.

3.  Low carbon, mild steel tubing is recommended.

4.  Must be frame-mounted in at least six places.

5.  Must consist of a configuration of front and rear hoops connected by tubing on the sides or side hoops.

6.  Driver’s head must not protrude outside cage with helmet on and strapped in driver’s seat.

7.  Must have minimum of one cross bar in top halo of roll cage.
8.  Roll cage must be securely supported and braced.

9.  Bar across back of engine with vertical bars and rub rails, or similar protection.

10.  No brace bars forward of cage may be higher than stock hood height.

11.  Main cage no further forward than engine plate.

C.  Frame & Suspension

            1.  Wheelbase 108” minimum

            2.  Top tubular A-arms are ok

            3.  No rack-n-pinion

            4.  No coil over suspension

            5.  Weight jacks are ok

            6.  No extra shocks or coils

            7.  No Aluminum shocks

            8.  Racing shocks allowed  

            9.  NO Schrader valves.

            10.  Rear shock placement is optional

            11.  No adjustable shocks

            12.  Extra holes in adjustable spring shackle is allowed

            13.  Stock pan hard bars on coil suspension only

            14.  Stock trailing arms only

            15.  No 2, 3 or 4 link suspension

   16. Adjustable lowering blocks ok

   17. No Composite Springs

D.  Steering

            1.  Original (OE) type

            2.  Quick release style ok

            3.  Steering quickners are ok

            4.  Steering box must remain in stock location

            E.  Wheels & Tires

            1.  Steel wheels only

            2.  Heavy duty studs and racing type lug nuts on all wheels

            3.  NO Wheel spacers

            4.  Bead lock on right rear only

            5.  8” max wheel size

            6.  Hoosier H500-8” tire max.

            7.  NO Bleeder Valve

             F.  Transmission

            1.  Any manual four speed or standard three speed will full gears and reverse

            2.  Scatter shield or 1/4" or more plate is required over bell housing

            3.  Triple disc ok. No smaller than 7 ¼

            4.  Auto trans. must use minimum 11” stock appearing torque converter

            5.  Must have visual inspection port no less than 1” in diameter in bell housing

           G.  Rear Ends

            1.  Any passenger car or half ton rear ends allowed

   2.  Interchanging and locking ok

   3.  Floaters rearends OK.  NO quick change.

H.  Brakes

            1.  Four wheel brakes in working condition at all times

            2.  Brake adjusters are ok (front to rear)

            3.  After-market master cylinders ok

            4.  Racing pedals ok

         I.  Engines

1. Engine must be OEM appearing, must be able to be used in conventional passenger car without alteration, GM with GM, Ford with Ford, Chrysler with Chrysler.
2. All cars must clearly display on the driver side which carburetor / engine option you are competing with. 350 or 500.

3. Any American make engine allowed

4. Steel heads, block and oil pan only

5. OEM firing order cannot be changed (GM 1-8-4-3-6-5-7-2)

6. Steel or aluminum water pumps allowed

7. No electric water pumps allowed

8. Wet sump oiling system only.

9. Accumulator allowed – cannot be located between seat and door bars.

10. Any intake with adapter until July 1, 2014……after that these are the only ones allowed: Weiand GM #7547 or 7547-1; Ford #7515, 8022; Chrysler #7545, 8022

11. Cooling lines allowed on aluminum intakes.


      1.  No cubic inch or compression limit.

      2. Flat tappet cam/lifters and stud-mounted rocker arms ok

      3. No shaft, offset or pedestal rocker arms.

      4. No titanium engine components

      5. No stud gridles

      6. No mushroom lifters, lifter diameter and configuration must match OEM passenger block.

      7. Full roller rocker arms allowed


      1. Max. 361 cubic inch(GM); 363(FORD); 370(CHRYSLER)

      2. GM approved block numbers are: 10105123, 10066034, 3892657, 3914660, 3914678, 3932388, 3932386, 3956618, 3970000, 3970006, 3970010, 3970014, 10066033, 10066036, 10243880, 14010207, 140010209, 14010287, 14010287, 14016376, 14016376, 14016379, 10054727, 14088528, 14088548, 14088552, 14093638, 14101148.

      3. Stroke must match block

      4. No 400 or larger cubic inch parts allowed

      5. Max. compression ratio is 10.5 to 1 NO tolerance.

      6. Flat top or dished pistons only.  NO gas ported pistons

      7. OEM or OEM appearing replacement steek crankshaft only. CANNOT be lightened.

      8. NO aerowing, bullnose, knife edge, undercut or drilling of second or third rod throws.

      9. OEM or OEM appearing replacement steel rods only. GM 5.7 inch 6 inch or GM Vortec rod part number 10108688 allowed.

    10. Cap screw allowed.

    11. NO splayed main caps.

    12. Conventional flat tappet cam & lifters ONLY.  CANNOT alter lifter bores.

    13. Mandatory one inch inspection holes in all pans. NO obstructions to crank & rods.





     1. Steel only

     2. Must be unaltered approved OEM & original minimum 76cc combustion chamber (GM).

    3. Only GM OEM approved head numbers are: FOR 2014 ONLY: 461 & 462 will be allowed….starting 2015 the ONLY heads allowed will be: 14079267, 3986336, 3986639, 3986339X, 3986388, 3932441, 376445, 3928454, 3932454, 3876487, 3973487, 3973487X, 3973493, 3951598, 468642, 330862, 333882, 3998920, 3998991, 3998993, 3998997, 3970126

    4. Max. size valves on these heads are 2.02 inch intake & 1.60 inch exhaust.

    5. May use stock replacement (SR) cylinder heads. Engine Quest (EQ) GM part #CH3501, (EQ) Chrysler part #CH318B. World Products Ford part #53030- 1.250 inch (+.015 tolerance) maximum OD valve springs. All SR heads must remain as produced, seat angles & valve sizes CAN NOT be changed; three angle valve job only (absolutely NO casting removal in valve pocket of EQ or World products head, for any reason).

     6. NO porting, polishing, or unapproved alterations allowed to ANY cylinder head. (exception is flat milling allowed)

      7. Guide plates, screw-in shoulder studs (7/16-inch MAX) & polylocks allowed.

      8. NO stud girdles

      9. Full roller rocker arms allowed. GM – 1.250inch (+.015 tolerance) max. OD valve springs, No beehive valve springs allowed. Unaltered OEM type harmonic balancer only.

15.  Engine set back: upper ball joint must be between first & second spark plug

16.  Headers with collectors pointed rearward; NO TRI-Y, CROSSOVER OR 180


      1. Unlimited cubic inch limit engines must use unaltered 350 c.f.m. Holley

 part #0-80787-1 with no modifications, or part # 0-7448 which may be modified to meet the specs of part #0-80787-1. Holley carburetor components only.

     2. Air bleeds cannot be removed, .076 inch maximum diameter. Limited cubic inch limit engine must use unaltered 500 c.f.m. Holley – part #0-4412, may be modified to Holley HP dorton part #0-80583-1 specs only.

     3. All float bowls must face forward

     4. Carburetor adapter/spacer allowed, maximum 1.20 inches thick, including gaskets.

             J.  Ignitions & Battery


            1.  Battery must be securely mounted and covered

            2.  Batteries in cockpit must be fully enclosed

           K.  Fuel Cells & Fuel

            1.  Fuel cells are mandatory @ 16gal max.

            2.  Must be inside trunk with screw of lock type cap

            3.  Must be set in steel box with safety straps and securely tight.

            4.  No alcohol.

            5.  Racing fuel or gas ok

            6.  No electric fuel pumps


 L.  Seats & Seat Belts

            1.  Helmets are required and must be a minimum of SA2005 with certification label inside helmet

2.  Helmets must be worn at all times car is on track

3.  SFI approved flame/fire retardant fire suits, gloves and shoes are mandatory

4.  An approved head/neck restraint system is mandatory (Hans, G-force, Hutchens or SFI rated neck collar

5.  Nomex underwear in highly recommended

6.  Seat belts and shoulder harness cannot be more than three years old

7.  The date of manufacture should remain visible at all times

7.  A lever-type quick release latch must be fastened to the lap belt

8.  All seat belts and shoulder harnesses must connect at the lap belt with a quick-release buckle acceptable to series officials

9.  Only custom manufactured racing aluminum seats acceptable to officials

10.  All seats should have padded rib protectors

11.  All seats are required to have a head rest on the right side

12.  All belts must be a minimum of three (3) inches wide

13.  Belts must be bolted to the roll cage with no less than 3/8inch bolt

14.  A center, crotch belt must be securely mounted to the lower seat frame at the bottom and to the lap seat belt on the top

15.  Where the belts pass through the seat edges, it must have a grommet installed, be rolled, and/or padded to prevent cutting of the belt

16.  Window nets are mandatory

17.  Windshield must have three (3) bars in front of driver.

           M.  Driver Uniform

            1.  Helmets, fire resistant driving suit, fire gloves, neck collars and racing shoes are mandatory

            N.  Weight

            1.  3000lbs. with driver or 3200 with fabricated frame or chassis

            2.  All bolt on weight must be securely mounted and pass safety inspection

            3.  No bolt on weight in the driver’s compartment

           O.  Drive Shaft

            1. Steel drive shafts only

            2. Must be painted white




DISCLAIMER: The rules and/or regulations set forth herein are designed to provide for the orderly conduct of racing events and to establish minimum acceptable requirements for such events. These rules shall govern the condition of all events, and by participating in these events, all participants are deemed to have complied with these rules. NO EXPRESSED OR IMPLIED WARRANTY OF SAFETY SHALL RESULT FROM PUBLICATIONS OF OR COMPLIANCE WITH THESE RULES AND/OR REGULATIONS. They are intended as a guide for the conduct of the sport and are in no way a guarantee against injury or death to a participant, spectator or official.The race director shall be empowered to permit reasonable and appropriate deviation from any of the specifications herein or impose any further restrictions that in his opinion do not alter the minimum acceptable requirements. NO EXPRESSED OR IMPLIED WARRANTY OF SAFETY SHALL RESULT FROM SUCH ALTERATION OF SPECIFICATIONS. Any interpretation or deviation of these rules is left to the discretion of the officials. Their decision is final.



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