2020 4 Cylinder Rules

All drivers are required to have their own Raceivers for one-way communication with race director official.  Transponders need to be attached using Westhold transponder pouch

Top 5 feature finishers will be required to go to tech area after the race.

  1. Four cylinder front or rear wheel drive passenger cars are eligible with a wheelbase between 92-107 inches.
  2. No full-frame cars allowed.
    1. Cars must utilize engine available in the car/body style being used.
    2. No all wheel driver. No all-wheel steer.
    3. A functioning diagnostic plug under the dash must be present.
    4. Aluminum allowed for hood, fenders, doors
  1. Only four cylinder naturally aspirated engines will be allowed. Engine must be completely stock as manufactured by factory including engine, driver train, ignition components, suspension components, and fuel system, except as noted below. Only the complete stock engine/drive train for the make and model as delivered from the factory may be used. No rotary engines.
  2. Stock intake manifold must be used with no modifications.
  3. Stock exhaust or headers allowed. Two-inch max diameter. Removal of smog, emission, air conditioning, and power steering parts are permitted.
  4. A complete exhaust system must run at least 24- inches of exhaust pipe. Removal of catalytic converter is allowed.
  5. Must use stock style starter. Battery may be relocated to an area behind driver. If so it must be secured and covered.
  6. Transmission must have working forward and reverse gears.
  7. Turbo chargers, super chargers,  or nitrous oxide are NOT allowed.
  1. All exterior trim, included lights, body moldings, mirrors, etc must be removed. Drivers and passenger door must be welded or bolted shut. Aluminum allowed for hood, fenders and doors. Roof, quarter panels, deck lid may be aluminum but must run a fuel cell and 1-1/2’ (.090) downtubes for cage mounting. NOTE: All Bodies subject to inspection and approval by the technical director.
  2. Cars must have stock frame and stock floor pan. All openings in firewall and floor pan must be covered. Firewall may be aluminum. Hood must be secured with a minimum of two hood pins each. (NOT BOLTS).
  3. Windshield must be replaced with 3 bars of 3/8” diameter. Bars must be welded to the roll cage in front of driver. All glass must be removed from the vehicle.
  4. Spoilers will be allowed Stock or Aftermarket. Aftermarket spoilers can be a maximum of five inches tall and 50 inches wide.
  5. All flammable interior trim is to be removed from passenger compartment and trunk. No removal of ANY interior sheet metal panels except in drivers door to make room for cage.   Heating and air conditioning box may be removed.
  6. Racing Seat is required.
  7. Steering column and pedals should remain stock. All air bag components must be removed. Collapsible steering column is recommended. Aftermarket pedals allowed.
  8. A full four-point standard cage is required. Cage must go completely from left to right side and may not protect just the driver’s side. All cars must have a minimum of three door bars on the driver’s side and two on passenger side. Minimum 1/8” thick plate must be welded or bolted to the outside of the driver’s door bars.  Cages must be welded or bolted to the floor of the car. All cars must have crush zones and a maximum of two rear down bars may be used to support the hoop. These bars may run from the top of the hoop behind the driver and extend to the front of the rear firewall. A single cross bar or “X” may be used between these down bars. Rear down bars MUST be attached to the trunk FLOOR.  Main cage must have a t least two bars running from left to right, between the upright, behind the driver.  One at floor level, and one at shoulder height of the driver.  Roll Cage tubing must be minimum 1 1/2″ diameter and .095 thickness.
  9. Main Shut-Off switch for electric fuel pump must be easily accessible by safety personnel, and clearly labeled as such.
  10. Cars must have tow chains or tow hooks front and back for tow truck pick up.
  11. Aftermarket body’s ok.
  12. Weight 2,200lbs with driver
  13. Cars must be neat in appearance and neatly numbered on BOTH SIDES and TOP.
  1. O.T. approved passenger car tires only. No “made for racing” tires.  Tires cab be 13, 14, or 15 inches maximum.  They can be 75,70,65, or 60 series.
  2. No wheel spacers of any kind allowed. Racing wheels are allowed.
  3. Steering and suspension shall remain stock and in stock location. OEM-style shocks, struts, and springs ONLY may be used. No heating or cutting of spring allowed.
  4. For cars that do not have camber adjustments built in from the factory, modification or existing parts, to allow for camber only adjustments will be allowed, but subject to technical director approval. Front Camber adjustment is 2 ¾” maximum. Rear camber adjustment is 1” maximum.
  5. All four brakes must remain stock. ABSOLUTELY NO ABS OR TRACTION CONTROL. All ABS sensors must be disabled.
  6. Cars that have fuel tank mounted in front of rear axle may use stock tank. If tank is not mounted in front of rear axle, a fuel cell or marine type tank must be used and securely mounted in the trunk area of the car. Trunk mounted tanks cannot be mounted within ten inches of the rear trunk panel and may not extend beyond the side frame rails. All fuel tank installations must be centered between the rear wheels.  Racing Fuel Cells HIGHLY recommended!
  7. No emergency brakes allowed.
  1. See “General Safety Rules” page for track specific safety rules.

Plymouth Speedway reserves the right to change, delete or add to rules throughout the racing season. The management reserves the right of interpretation of all rules and the right to inspect and reject any car and/or driver, crew member, etc. during the racing program.


For any questions on the Plymouth Speedway rules, please call Tech Director Chris Hunter 765-319-9557