THUNDER BOMBER RULES

** Thunder Bomber // General **

1.) No nitrous or traction control. 

2.) Cars must be neat in appearance.

3.) Any driver in this division may compete in one other division on the same night.

4.) Car weight must be greater than 3300 lbs. after the race with the driver.

5.) More weight may be added to any dominant car at the track’s discretion at any time.

6.) Cars must have numbers on sides and top readable by scorer.

7.) Stock unless otherwise noted.

** Thunder Bomber // Body **

1.) Visual protest only.

2.) No late model noses or tails.

3.) 1968 or newer American made car, no station wagons, trucks, jeeps, convertibles, mustangs, or pony cars.

4.) Rear end of the car must be closed, no holes or flaps or hinges.

5.) Must have a deck lid.

6.) Front and rear fenders may be fabricated.

7.) No side spoilers.

8.) Rear spoiler may not exceed 60” wide by 6” tall with no spill plates.

9.) Rear spoiler shall not exceed 48” from ground to top of spoiler.

10.) Roof may be replaced if necessary but must be 48” x 50”.

11.) Aluminum may be used for doors and fenders.

12.) A minimum of 13” for all door and rear glass openings.

13.) Interior may be boxed in.

14.) Front and rear bumpers may be rubber like, stock appearing and no cow scoop.

15.) May pull air from inside the car, no forced air.

16.) Front or rear inside wheel wells may be cut or removed.

17.) All firewall holes must be covered.

18.) If the firewall is not stock it must be 3,350 lbs. Min and the extra weight if needed must be mounted on the passenger side door frame rail.

19.) The weight must be posted on the passenger front side of the car if the weight is 3350.

20.) Dash may be fabricated with steel or aluminum, but no higher than original.

21.) Gutting the trunk and hood is permitted.

22.) Lexan is okay for side and rear windows.

23.) Bumper will not go past the inside of the rear tire.

24.) No mirrors are allowed.

** Thunder Bomber // Frame **

1.) Frame must match the make and model of the car, +/-1”.

2.) Frame may not be shortened, stock only, no X braces or frame cutting.

3.) Length between spring eyes must be stock.

4.) The wheel base must be stock.

5.) Engine placement cannot be set back any further than the #1 spark plug, inline with the ball joints.

6.) Radiator must be in stock location, may be aluminum.

7.) Fuel cell must be inside of the trunk with a firewall between the cell and driver.

8.) Seat must be securely fastened to the frame and/or roll cage.

** Thunder Bomber // Suspension **

1.) Suspension must be stock unless noted.

2.) Racing springs with adjustable buckets are okay.

3.) No adjustable lowering blocks, 4” max of fixed blocks.

4.) Top A frame may be tube type, non-adjustable, bolt in ball joints only on top A frame.

5.) Heavy duty OEM steering and suspension parts are okay.

6.) Leaf or coil springs may be changed to a stronger type of the same spring. 

7.) Cutting coil springs are okay, rear coil spring shims are okay.

8.) Adjustable or non-adjustable spring buckets are okay.

9.) Front shocks must be in stock location

10.) Rear adjustable buckets are okay.

11.) All chassis hook up points must be in stock location.

12.) Rear shock location must be stock on top but may be moved on bottom for travel length only.

13.) Changing the angle of rear shocks is not allowed. 

14.) Top rear trailing arms may be cut for pinion angle only, no mono-balls in any trailing arms.

15.) Leaf spring perches and shackles may be reset for pinion angle

16.) Aftermarket replacement bushing in A frames are okay but no Heim Joints.

** Thunder Bomber // Shocks **

1.)  Stock length push rods and stock diameter required. Aftermarket and hardened are allowed.

2.) No Heim Joints on any shocks.

** Thunder Bomber // Wheels & Tires **

1.) Steel wheels must be used, 8” wide, +/-.25”, 14 “or 15”. Must be the same all around.

2.) Tires may be ANY 70, 75, or 78 series street legal DOT tires.

3.) Bead locks are allowed.

4.) Wheel spacers and offsets are allowed.

** Thunder Bomber // Brakes **

1.) Stock brakes for make and model.

2.) OEM calipers only.

3.) Dual master cylinder is allowed. Adjusters are allowed. 

4.) No gun-drilled or scalloped rotors.

** Thunder Bomber // Flywheel & Clutch **

1.) Stock steel flywheel, 14 lbs. minimum.

2.) Stock type clutch and pressure plate, 10.5” minimum.

3.) Hydraulic or aftermarket throw out bearing is allowed.

4.) 3/16” steel shield over bell housing required or blow-proof bell housing mandatory. 

** Thunder Bomber // Transmission **

1.) Stock type automatic transmission with working torque converter. 11” minimum. 

2.) Transmission cooler is allowed. No power glides.

3.) No lightening or polishing of any gears.

4.) Must have all working gears.

** Thunder Bomber // Driveshaft **

1.) Stock for make and model of car. 2” steel replacement is allowed.  

2.) No carbon fiber or aluminum allowed.

3.) Safety loop required around front of drive shaft. 

** Thunder Bomber // Ignition **

1.) Stock type distributor ignition only.  

2.) Stock firing order only.

3.) No high-performance HEI or distributors with external boxes. 

** Thunder Bomber // Rear Ends **

1.) May use GM 10 or 12 bolt, any gear.

2.) 9” ford floater or non floater allowed.

3.) No gun drilled axles.

4.) No lightening or polishing of any parts.

5.) All components must be steel.

** Thunder Bomber // Engine **

1.) Any OEM one or two piece seal block max 363 cubic inches assembled.

2.) Stock location only, aftermarket mounts are allowed.

3.) Approved repair parts only.

4.) ARP rod bolts are allowed if standard 3/8”.

5.) Stock cast replacement crankshafts are allowed.

6.) No knife edging or lightening allowed.

7.) Minimum crankshaft weight 48 lbs.

8.) Stroke must remain stock.

9.) Stock rods with stock journals and pin diameters only.

10.) Aftermarket SFI balancers are allowed.

11.) Aluminum racing water pumps are allowed.

12.) Racing pulleys are allowed, no serpentine belts.

13.) Aftermarket fuel pumps are allowed.

** Thunder Bomber // Heads **

1.) Any open chamber is allowed with following restrictions:

2.) Aftermarket valve covers are allowed.

3.) Screw-in or pinned rocker screws are allowed. Screw in studs may not have hex heads. No guide plates.

4.) Vortex is allowed

5.) Stock size of valve only for make and model, steel only.

6.) Z28 valve springs are allowed.

7.) No 3 angle or competition valve job, no cutting under 45 degrees.

8.) Shims under springs maximum .060” under each spring.

9.) Stock rocker arms only, no long slot or roller rockers.

10.) Off set locks are allowed, but no shims allowed.

11.) Stock valve stem only.

12.) No porting or polishing.

** Thunder Bomber // Intake Manifold **

1.) Cannot port and polish intake.

** Thunder Bomber // Carburetor **

1.) Stock 2 or 4 barrel.  

2.) No modifications. However, drivers can remove the choke flap only. 

3.) Box stock Holley 1850 is allowed with Mr. Gasket 1932 adapter and 2 each .070 thick gaskets. 

** Thunder Bomber // Cam **

1.) Stock or Cloyes C-3023X timing chain only, no cam buttons.

2.) .390-.410 lift, 112 degree lobe separation, +/-1 degree.

3.) Stock cam or Sealed Power CS-274, Melling CCS-2 or Comp 12-105-3 are approved.

4.) Hydraulic lifters only.

Amendment: There have been some interest in drivers wanting to run Fords. However, there was no cam number in the rules. These are the cams that are equal to the Chevy:

- Ford Elgin E750-S

- Chrysler Elgin E577-S

** Thunder Bomber // Safety rules**

1.) Window nets are mandatory. Sprint-style window nets will not be permitted. Good quality full face racing helmets or DOT approved helmets are required.

2.) Minimum single-layer fire suit required. (SA 3.2A specification recommended) 

3.) Fire proof gloves are strongly recommended. (SFI 3.3 specification recommended) 

4.) A 4 or 5 point harness, properly mounted per manufacturers’ specifications, is required.

5.) Belts must have been manufactured in the last 5 years. Any worn, abraded or torn belts must be replaced. 

6.) A 5 lb. (or greater) fire extinguisher should be securely mounted within the drivers’ reach. 

7.) Only racing-type seats, properly mounted per manufacturers’ specifications, are allowed. 

8.) A head-and-neck restraint system is mandatory (SFI 16.1 compliant recommended).

9.) A firewall must be in place between the driver compartment and fuel cells, fuel lines, or tanks.

10.) Safety chains must remain securely fastened on the front and rear of the racecar at all times.  

11.) Any time a car is on the track all safety gear is required.

12.) Must have a fire extinguisher and seat belts that are up to date. Fire suppression is recommended.

13.) Anytime a car is on the track all safety gear is required.

14.) Race receivers are mandatory. 

15.) No radios allowed.

24.) Fire extinguisher in car is mandatory 

25.) Any time a car is on the track all safety gear is required.

Safety chains must remain securely fastened on the front and rear of the car at all times or you will be immediately disqualified.

Competitors must present cars for inspection prior to participating in any racing event. A pre-race inspection will be made ONLY to ensure safety protocols have been adhered to. Questions of legality can and will be answered during the pre-race inspection if asked by an entrant. No guarantee of legality shall be expressed or implied during pre-race inspection. Legality will be determined in post-race inspection. Fairgrounds Raceway has final ruling on all questions of legality. 

Fairgrounds Raceway officials have every right to change the rules if deemed necessary at any point during the season. Officials may be open to changing rules if it is best for the majority of the class.

Ⓒ 2025 Fairgrounds Raceway

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