Thumper Rules 2013 (10/01/12)
A. Car & Body (BODY DIAGRAM AT BOTTOM OF PAGE)
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. Stock frame
3. Top tubular A-arms are ok
4. No rack-n-pinion
5. No coil over suspension
6. Weight jacks are ok
7. No extra shocks or coils
8. No Aluminum shocks
9. Racing shocks allowed
10. NO Schrader valves.
11. Rear shock placement is optional
12. No adjustable shocks
13. Extra holes in adjustable spring shackle is allowed
14. Stock pan hard bars on coil suspension only
15. Stock trailing arms only
16. No 2, 3 or 4 link suspension
17. Adjustable lowering blocks ok
18. No Composite Springs
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
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.
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
1. Engines must be stock for make and model (ex: ford to ford, gm to gm)
2. Engine set back: upper ball joint must be between front two spark plugs
3. Any flat tappet camshaft
4. Nothing over .060 overbore
5. Flat top pistons only
6. Piston cannot protrude past top on engine block
7. Any manifold allowed
8. 1” adaptor or spacers only
9. 1 two or four barrel carburetor; 2 throttle return springs MANDATORY
10. Max. 410 c.i.
11. Stock crankshaft
12. Stock appearing steel rods
13. Stock OEM heads only. No Aftermarket, Bow Tie, Turbo heads SVO, direct connection, Vortec, Angle plug or aluminum heads
14. Guide plates, polly locks, screw in studs and roller rockers ok
15. Must run original diameter spring
16. Machine work for larger springs ok
17. Max valve spring size 1.250
18. No taper springs allowed
19. No machine work tolerated
20. No stroker motors (ex. Chevy 377-383)
21. Stud girdles are allowed
22. No aftermarket shaft mounted rocker arms.
23. Headers with collectors pointed rearward; NO TRI-Y, CROSSOVER OR 180 TYPE
24. Cars must be equipped with self-starter in stock location
J. Ignitions & Battery
ALL CARS MUST USE MAX. 7800RPM REV LIMITER CHIP. THIS MAY BE ACCOMPLISHED USING ONE, NON-ADJUSTABLE, 12 VOLT IGNITION BOX WITH ONE HIGH END REV LIMITER SETTING OR AN INTERNAL SETTING INSIDE BOX. MSD #8728 REV CONTROL OR MSD #8738 ADDITIONAL REV CONTROL BOX ALLOWED. PRESET CRANE #6000-6478 IGNITION BOX ALLOWED. NO ADDITIONAL IGNITION ACCESSORIES ALLOWED. ALL COMPONENTS MUST BE OUT OF REACH OF DRIVER, BUT ACCESSIBLE FOR INSEPECTION. NO MAGNETOS OR CRANK TRIGGERS
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
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.