2013 Modified Rules
All General and
Safety Rules apply.
A. Body, Chassis, and Weight
1. All cars must have steel plating at least 18 ga. or 0.049 inches
thick on the drivers side door bars and floor board.
2. Composite body parts are not allowed except for roof leading edge
rock guards and hood scoops.
3. The body must be approximately the same width front to back and be
near parallel to the OEM frame.
4. The nose panel must remain within the perimeter of the front bumper.
5. Windows must have a suitable opening to allow for safe entry and exit
and assistance from emergency personnel.
6. Sail panels may not extend forward past the back of the seat and must
be separate from spoiler side braces.
7. Rear spoilers may not exceed 6 in height when measured from the deck
to the top of the spoiler. Side panels may be 7 in height when measured
from the deck to the top of the side panel. The spoiler must match the
width of the car. Two braces will be allowed in the center span of the
spoiler, between the side panels. The height of the braces shall not
exceed the height of the spoiler. It is highly recommended that the
spoiler be made of clear Lexan to aid in visibility for other drivers.
8. Wicker bills on the nose must not exceed 4 in height off of the face
of the nose.
9. A maximum of 6 of interior rake front to back is allowed if the rake
starts at the front edge of the interior and continues to the back edge
of the interior. If the rake starts behind the seat, only 3 or total
rake is allowed. or The back of the car must not exceed 42 when
measured from the ground to the top of the deck.
10. A maximum of 5 of total rake front to back is allowed in the roof.
11. All cars must have at least 3 bars in the windshield area in front
of the driver. See general safety rules for further explanation.
12. All cars must have a properly installed racing seat. The bottom of
the seat must not extend below the bottom of the frame rails.
13. The driver must be completely sealed off from the engine, drivetrain,
fuel cell, battery, etc.
14. A stock width 1964 or newer OEM or OEM replacement rear wheel drive
passenger car frame must be used. Sports car frames are not allowed.
15. The wheelbase must be between 108 and 112 inches.
16. Front suspension components may be altered. Lower control arm mounts
must remain in stock location.
17. Bump stops are not allowed.
18. Rack and pinion steering is not allowed.
19. OEM style steering box, idler arm, pitman arm, drag link, and inner
tie rod ends must be used and must match the frame. Quick steer may be
20. OEM style spindles must be used but do not have to match the frame.
Spindles must be right and left and of same design. Tubular spindles are
21. A quick release steering wheel must be used.
22. Only one shock per corner plus one in the pull bar area is allowed.
Zero/Zero valving shock eliminators are permitted.
23. Neither internal nor external bump stops are allowed, except on the
panhard and pull bars.
24. Front coil over and remote reservoir shocks are not allowed.
25. One steel, non-progressive coil spring per wheel plus one spring in
the pull bar area only. The pull bar spring may be progressive. Steel or
composite leaf springs may be used.
26. Any coil spring used must be a minimum 4.5 inch outside diameter.
27. Torsion bars, air bag style springs, inner liners, and spring
rubbers are not allowed.
28. Independent rear suspensions are not allowed.
29. All cars must have a functioning brake on all four wheels.
30. The only driver adjustable instrument allowed in the car is a front
to rear brake proportioning valve.
31. All cars must have a steel front and rear bumper. The front bumper
must have a minimum of two bars with the bottom bar parallel to the
ground and the top bar directly above it. The bars must measure at least
6.5 inches apart center to center. The rear bumper must extend no more
than 6 inches past the rear deck and have at least one upright from the
bumper to the fuel cell guard. All bumper material must be a minimum
1.25 inch outside diameter and 0.065 inch wall thickness.
32. The car and driver must weigh 2350 pounds after each race.
33. Cars running aluminum heads must add fifty pounds of weight in front
of the engine plate (twenty five pounds per side).
34. All weight must be painted white with car number and securely
fastened using solid steel bolts with a minimum diameter of 0.5 inches.
The weight must be mounted below the interior deck, outside the driver
compartment, and inside the body.
B. Engine and Drivetrain
1. The radiator must be mounted in front of the engine.
2. The rear of the engine must be mounted at least 72 inches in front of
the rear axle center line.
3. The engine must not be offset more than 2 inches from the cross
member center line and must be level.
4. Roller cams and aluminum heads are legal. See section A for weight
requirements if running aluminum heads.
5. Aluminum blocks are not allowed.
6. All cars must use only one battery up to 16 volts. The battery must
be mounted securely between the frame rails.
7. Electronic traction control devices, timing retard controls, digital
gauges, and electronic or computer monitoring systems capable of storing
or transmitting data are not allowed. An analog memory tachometer may be
8. Crank triggers and magnetos are not allowed.
9. Aftermarket transmissions are legal.
10. All cars must have a steel scatter-proof bell housing if using an
11. All cars must have neutral, reverse, and at least two forward gears.
Cars must start in neutral using a working starter and then go into
forward and reverse gears.
12. All drive shafts must use steel slip yokes, be at least 2 inches in
diameter, be painted white with car number, and have a 360 degree loop
mounted approximately 6 inches behind the front u-joint.
13. Cambered rear ends, torque dividing differentials, and traction
control devices are not allowed.
14. Quick-change rear ends are legal.
15. No traction control devices of any kind are permitted.
C. Carb and Fuel
1. All cars must run a single naturally aspirated carburetor.
2. Mechanical or belt driven fuel systems must be used.
3. The required fuel cell must be securely mounted and well protected by
4. Check valves must be used on all vents.
5. Alcohol or racing gas may be used. No additives are permitted except
for top-end lube.
D. Tires and Wheels
1. All cars must run 8 steel wheels. Wheels do not have to have
sanctioning body stamp.
2. Beadlocks are allowed and are recommended on the right rear.
3. Approved tires-American Racer KK704, KK704 Short, or Hoosier G60-15
with or without stamp.
4. Tires may be grooved, siped, and ground but may not be chemically
softened or conditioned.