Open Wheel Modified Rules

Open Wheel Modified



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/her opinion do not alter the minimum acceptable requirements. NO EXPRESSED OR IMPLIED WARRANTY OF SAFETY SHALL RESULT FROM SUCH ALTERATION OF SPECIFICATIONS. Any interpretation of deviation of these rules is left to discretion of the officials. Their decision is final.

The Management of Huntsville Speedway

Warning!  If you attempt to abuse the minimal amount of rules set forth by Huntsville Speedway for the 2021 Open Wheel Modified Division, we will have no choice but to refuse your request for participating.  Just because the rules don’t say you can’t, does not mean that you can!


Refer to Huntsville Speedway’s General Rules for a full list of rules regarding driver, pit and car safety.

On Track

1.  All starts and restarts will be mandatory double file, second place car to the outside and so forth.

2.  Single file restart with 5 laps or less to go.

3.  Racing radios and neck restraints recommended.


1. No dry sump oiling system.

2.  Aluminum engine heads allowed with no penalty. 

3. Cooling system may be modified; antifreeze shall not be used.  $250 fine.

4.  Only one carburetor allowed.  No fuel injection on any kind.

5. Any V-8 American Cast iron engine block may be used as long as rear of engine (bell housing flange) is mounted at least 72” forward from the centerline of rear axle. Engine offset must be kept within 2” of centerline of front cross member. Minimum engine height will be 11” from ground to front of center of crankshaft at a 4” frame height.

6.  No electric fuel pumps allowed. 

7.  No external ignition crank triggers.

8.  No electronic traction control devices of any kind.


1. 58% maximum left side weight.

2. Minimum 2550 pounds, maximum 2800.

3.  Only 1 pound per lap fuel burn off allowed.


1. Manual Transmissions only.  Transmissions must have 2 forward and 1 reverse gears in working order.

2.  All transmissions must be clutch operated.  Any driver choosing to use a clutch larger than 7 ¼” must also use a steel bellhousing.  Flexplate must be SFI rated.

3.  No “in and out” gear boxes or automatic transmissions.

Rear End

1. Floater or quick change is allowed.

2. No Wide Five hubs, no aluminum axle tubes.

3. Drive shaft must be painted white.

Brakes, Wheels, and Tires

1. Must run one brake per wheel. Single piston, steel caliper only.

2.  Add 5 lbs per aluminum single piston caliper.

3.  Add 10 lbs per multi piston caliper.

4.  Stock OEM size steel rotors only.

5.  8” wide steel racing wheels only.  No wheel weights of any kind.

6.  Tire – American Racer KK704 only – must have Huntsville Speedway or Sayre Speedway stamp.  (Subject to change for special events)


1. OEM Factory production steel frames only.  No sports car frames. Frame must be fully intact on right hand side of driver with factory specs -36” forward from centerline of rear end housing. Front bumper horns may be removed in front of steering gear box. No widening or narrowing of frame allowed. Notching allowed for tie rod arm clearance, front cross member may be notched and boxed for radiator and/or steering clearance.  Left side top frame rail can be removed inside cockpit.  Anything else will be subject to a weight penalty, depending on the advantage you might have over your competitors.

2. Fuel cell cannot be any lower than rear axel housing and mounted behind the rear axel.  Must have a fuel cell protector bar at least 1” lower than fuel cell frame.

3.  Minimum frame height at all times is 4”.

4.  Minimum wheelbase 108”.


1. Aftermarket tubular upper control arms permitted. Bottom control arms must be unaltered and in stock location. NO aftermarket lower control arms permitted.

2. No rack and pinion steering allowed.

3. Front springs 5”minimum in diameter. Rear springs 4.5” minimum in diameter.  Minimum of 500 pounds front spring rate.

4. Stock passenger car spindles or fabricated spindles allowed but must be steel.

5. No internal or external bump stops, frame stops or suspension limiters of any kind.

6. Only non adjustable steel or Aluminum bodied shocks permitted. 

7. Schrader valves permitted.  

8. Maximum overall track width shall not exceed 80” from outside of the right side tire to outside of the left side tire and will be measured at hub height.

Body Specifications

1. Only one rear spoiler allowed at a maximum of 8” height and cannot be mounted past rear quarter panel or exceed the width of the body. No side foils behind spoiler. Total material is not to exceed 8” in height from rear deck cover.

2. Roof height must be minimum of 42” and maximum of 52″

3.  Body sides must be straight front to rear, 120” maximum length starting at the rear of engine block (bell housing flange) on both sides of car.

4.  Maximum body width is 66”.

5.  Maximum body rake is 6” from lowest point on A arm post to the rear spoiler lower mounting location.

6.  Five Star style composite asphalt nose – Maximum width of 43 1/2” not to be measured at chin spoiler.  

Hand Fabricated nose – Maximum width of 43 ½”, two 2 ½” fins allowed on both side end caps of nose.  No other fins, splitters, or ledges allowed anywhere.


1. 1/8” Polycarbonate/Lexan Windshield is highly recommended. Full windshield is preferred.


1.  Refer to Huntsville Speedway’s General Rules for a full list of rules regarding interior safety.