Introduction:
The NAPA Thunders are designed to be a pure stock racing class. The purpose of this class is safe, fun, low cost, close, competitive racing. An attempt will be made to keep this class stock as much as possible and the spirit of the rule is what we are after and we shall do whatever we can to KEEP the NAPA THUNDERS affordable. Use of OEM (original equipment manufacturer) parts is part of what will make this class work.
We reserve the right to change, omit, add any rules we deem responsible for safety, and the betterment of competition.
Drivers must be at least 14 years old.
Car / Truck options:
Open to any passenger car or 2-WD light duty pickup truck from 1960 – present date. No Jeeps, Corvettes, convertibles, Citations, Vegas, Corvair, Falcons, gremlins, Monza types, 4-WD’s, sports cars, or compact cars. Vehicles not covered under these exclusions do not mean they are pure stock. Consult tech inspector as to the legality of the vehicle before building. Some models may not be included in the above exclusions. To avoid disappointment and expense, please check with us before you build a car.
Car/Pick-up Specifications:
Any make or model American production car or pick-up trucks. Metric (Toyota, Honda. Nissan, etc) pickups allowed but not small import compact cars. Wheelbase on any Thunder will be a minimum of 100 inches. Must be 2 wheel drive cars or pick-ups either front or rear wheel drive but only as it came out from the factory with no wheelbase modifications.
(A) Wheelbase to Engine type rule:
- Thunders that are 100 – 107 inches of wheelbase must use 4 cylinder or 6 cylinder engines. If below 108 inches of wheelbase racer will be 6 or 4 cylinder powered. Over 108 inch wheelbase can use stock unlimited size engine.
- Note: No v8 powered Camaro, Mustang, Firebird, or cars of similar style and type.
- No factory specials allowed (Cobra Jets-SS’s GTX’s Z28, Boss, etc) remember if you are not sure contact us now.
- Must stay within the same manufacture family (FORD to FORD, GM to GM, DODGE to CHRYSLER).
(B) Bodies, Frames, Suspension and more:
- Must retain stock bodies. Hood scoops that do not interfere with driver’s vision are allowed. Hood scoops must not be performance enhancing (no holes in hood that direct air to carburetor or fuel system).
- A rear spoiler that is the no wider than width of the trunk lid or tail gate is allowed. The Spoiler must not be over 12 inches long or 12 inches taller than the mounting point which must be at the rear of trunk lid or tailgate.
- Body trimming for tire clearance and removing inner fenders, and inner door skin for roll bar clearance is allowed. Hood and trunk lid and trunk area may be gutted. Firewall must remain intact with any holes to driver’s compartment covered. Uni-bodies may be braced for safety (driver’s compartment area only – that allows for under the car also). NO adjustable springs or weight jacks on the car. No added weight to the cars.
(C) All glass must be removed. All trim, headlights, taillights, turn signals, marker lights, mirrors, carpet, headliner, rear seat, passenger seat, door panels and antennas must be removed. Horn may be left intact and working. Brake lamp mounted in rear windshield area is advised and allowed
(D) All doors must be welded – Air bags must be removed.
(E) Must have front and rear tow hooks or chains for the wrecker.
(F) Must be tastefully and cleanly painted, with Car numbers on the doors and roof.
(G) Bumpers and nose pieces– Must be stock appearing – aftermarket grill or nose pieces are allowed. Hydraulic Bumpers must be chained on.
(H) Battery – Must be relocated and mounted securely and covered – battery must be placed in the rear passenger seating area. Battery must be mounted in a safe and secure manner inside the car and in a marine type box. Battery cables running in the passenger area of the car must be mounted in a safe and secure manner.
(I) Body bumpers or nerf bars down the sides of the car to protect the body area are allowed and recommended. To help protect the sides of the car from the bumper and bumper, nerf bars are allowed on each side of car. That bar or pipe must not be over 2 inch pipe or tubing.
(J) Exhaust – Must be stock manifolds and that means no modifications or performance enhanced. NO HEADERS allowed (even if OEM).
(K) Stock Engine – Any 100% stock V-8 or 6 or 4 cylinder (check wheelbase rules). Gasoline engine only. No performance parts of any kind. No superchargers or turbo’s on v-6 or v-8. The 4 cylinder cars may use stock OEM turbo’s or superchargers, if it came on that make and model. No one-off specials like Shelby’s and Buick Grand Nationals, etc. Remember Stock parts may not be altered either, NO BREZENSKI or performance enhanced Manifolds. A/C, EGR, heater, cruise control may be removed. The engine match the Body (Chevy to GMC, Dodge to Chrysler, Ford to Mercury)
(L) Must use 2 barrel stock carburetors, stock fuel injection, and stock fuel pumps. No Holley carburetors. Carburetor Motors must pull 16” or greater (17, 18,19) of vacuum at 1000 rpm that is checked by the carburetor. (Zero Tolerance). Must have vacuum supply line accessible to the fender well.
(M) No aftermarket electric fuel pumps. Stock fuel pumps are allowed on fuel injected cars. Must be hooked into the main power switch of the car so when the switch is off so is the power to the fuel pump.
(N) Motors must be in original position. No motor set back or offset. Motor mounts do not have to be stock.
(O) Transmission: OEM Manual transmission to automatic and Automatic to Manual is car builder’s choice. Transmission and Clutch assembly and linkages must be of smooth working order and must be mounted safely. No mini clutches!
(P) Tires / Wheels: Maximum tires size 60 series DOT legal street tires or IMCA Modified and IMCA Stock Car Tires allowed. Also asphalt take offs are allowed. No racing style re-caps. No mud and snow tires, all weather is allowed. OEM maximum tire width 8”and maximum diameter 16 inches. 1” lug nuts and studs allowed and recommended. Racing wheels are recommended.
(Q) Suspension: All suspension and steering parts must be stock for that car. No modifying of OEM parts, no mixing and matching, no relocating of mounts, stock springs without modifications with stock length. Locking of rear ends is allowed as well as FORD 9 inch rear ends are allowed because of axle safety. Mini spools are allowed on rear ends. Racing steering wheels and steering quickener allowed.
Springs: Coil springs must be the same left to right on the car. To clarify that means the same diameter coils as well as coil length. Must maintain stock ride height.
(R) Ignition: Must use stock OEM type ignition – no aftermarket HEI distributers or coils. Keep it stock!
(S) Safety:
- A six 6-point well constructed roll cage is mandatory. Minimum roll cage should have at one post by each windshield post and two behind the driver with all four connected at the top with a roof hoop. You must have an angle brace from the driver’s front of the roof hoop to the right rear of the roof hoop. Roll bars are allowed through the front or rear firewalls for 2010. You must have an angle brace running from the upper right corner to the lower left corner behind the driver. The two back bars must run from the top left and top right of the roof hoop to the rear of the car. We recommend a protective bar running from the front left cage post forward and down to the frame to protect the driver’s foot area. There should be a minimum of 3” clearance from the roll cage to the driver’s head. Roll Cage padding is recommended.
- Windshield area recommended having four (4) 3/8”windshield bars. Must have mesh screen on at least driver’s side of where the windshield area is. Once inch square mesh, painted black recommended.
- Minimum of three (3) driver’s side door bars constructed as part of the roll cage. Must have plating and reinforcements between the bars.
- Gussets on all welds recommended. Must have minimum 5-point quick release seat belts attached to roll cage, Racing Helmet required (Snell m2005 min SA2005 recommended). The driver must wear a long sleeve fire retardant suit also recommended is racing fire retardant gloves,
- underwear, and shoes.
- Stock gas tank must be removed and replaced with a fuel cell or a marine type tank enclosed in a metal box. Metal tank fuel tank protection bars recommended. Fuel tank must be securely mounted to the trunk floor.
- If other than a key ignition switch then that replacement switch be painted red with on and off plainly marked. Must be easily accessible to driver and track crew.
- Must use racing fiberglass or metal racing seat. Fiberglass seat must have a steel reinforcing backer.
- Window net recommended for drivers door window area. Should have a latch at top of window that driver and safety crew can easily release.
- Fuel: Pump gas only, No Race Gas, no additives, and no NOS…. If car is using rubber fuel lines they must be encased in metal pipe as they as they pass thru the driver’s compartment. No performance enhancing additives are allowed to the fuel.
- Numbers must be painted on front doors a minimum of 18 inches high, on the roof a minimum of 24 inches high, and a minimum of 3 inches wide. All numbers must be of a contrasting color to the body, and easy to read. NO chrome numbers allowed. Vinyl numbers and letters are allowed. Sponsors names and other lettering must be neat and not interfere with the numbers.
- If car is set-up for passengers, it must have same safety equipment and roll cage type and protection as driver side. Passenger is required to have same safety equipment as driver.
- Crash damage: These cars are going to be involved in a crash once in a while it is just a racing thing. Cars will need to be repaired to be safe and the appearance needs to be good also.
