Pro Stock 4WD Rules

Drawbars

  1. Hitch height to be a maximum of 26″ at hook point.
  2. Drawbar length is a min. 36% of the wheelbase before, during and after pull.
  3. Trucks where the drawbar height adjustment link is attached to the rear differential housing, the attaching point must be at axle centerline or below.

Clutches and Flywheels

  1. Steel bell housings or scatter blankets are required.
  2. The flywheel, and or flex plate, clutch and pressure plate components must be SFI approved components.
  3. All bell housings must be flush on the inside surface.
  4. SFI certified bell housing with Crower stand adjustment slot are acceptable.
  5. Add four additional bolts to fasten the bell housing to block saver plate. These bolts are to be 3/8- inch grade 5, along with 5 evenly spaced bolts between block saver and bell housing on lower half.
  6. Only mechanically activated clutches allowed.

Engines

  1. Maximum engine displacement is 485 c.i. Allowed 1% for wear.
  2. Cast iron blocks only. Aluminum blocks allowed.
  3. Aluminum cylinder heads are allowed. Cylinder head must have an O.E.M. intake bolt pattern. No spread port big block Chevrolet heads allowed.
  4. Any cast iron cylinder head allowed.
  5. Engine must be naturally aspirated with a single four barrel carburetor.  No split or spread carburetors allowed.
  6. Any cast intake manifold allowed. No tunnel ram intakes allowed. No sheet metal or composite intake manifolds allowed.
  7. Any ignition will be allowed.

Chassis

  1. Maximum wheelbase will be 134″. Body sheet metal must conform to wheelbase
  2. Flip top and fiberglass bodies are allowed. Driver’s door must be operable.
  3. Trucks must have safety glass or Plexiglas in windshield and rear window
  4. Rear of block can be no more forward than 12″ from the center of the front axle tube.
  5. Weight box maximum width 84″, not to exceed 60″ forward from top center position of front axle tube.
  6. Solid suspension is allowed only in the rear.
  7. Drive train will consist of the following: any front axle or any rear axle, no planetary rears allowed. Must have OEM frame rails
  8. Any aftermarket transmissions and transfer cases allowed.
  9. Engine does not have to conform to body/chassis being entered.
  10. Dirt deflectors of any kind are not allowed.
  11. Any pneumatic or hydraulic suspension components must not be controlled from the cab

Exhaust Systems

  1. Exhaust system must run down and back or up through the hood. Adequate clearance around headers will be allowed to permit opening the hood. If you burn alcohol you must run with the headers up. You can also run exhaust spacers.

Fuel and Fuel Containers

  1. Alcohol and gasoline fuel allowed. No additives are allowed in fuel except those additives blended by the fuel manufacturer or refinery
  2. Fuel cells only, no factory tanks allowed.
  3. No fuel cells in driver’s compartment.
  4. Fuel tanks must be in open area and cannot be any farther forward that 60” from center of the axle tube.

Kill Switches

  1. Kill switch with a 2″ diameter ring required. It must break power to the ignition and electric fuel pump. The switch must be located approx. 12″ above hitch.
  2. Track officials and/or tech inspectors have the option of checking kill switches as they feel is adequate at any event. It is recommended that all kill switches be check on all competing vehicles at every event.

Safety

  1. Engine must be shielded at least .060″ thickness. Height to extend to bottom of cylinder head and must cover the entire length of the engine. No unnecessary holes in the firewall. Any engine driven fan must be shrouded 360 degrees.
  2. All trucks equipped with a SFI harmonic balancer.
  3. Reverse light required at the rear of the vehicle and inside the cab. Both are to be activated by the gearshift.
  4. All driveline U-joints are to be enclosed 360 degrees using 1/4″ steel or 5/16″ aluminum and must be a minimum of 6″ wide with a maximum of 2″ clearance from the U-joint.
  5. All drive shafts between the transmission and transfer case must be completely enclosed with ¼” steel or 5/16” aluminum and fastened securely.
  6. All drive shafts must also have 3 loops 1/4″ thick steel x 3/4″ wide minimum.
  7. No cables, chains, or cast metal for loops.
  8. If an Illiana Pullers Association track official or tech official feels a vehicle is unsafe, they have the right not to allow vehicle to pull. Track official or tech official has the right to bar a competition vehicle from competing if he or she believes that the vehicle has a potential safety problem.
  9. All pulling vehicles must be equipped with a minimum of 2 lbs. Halon type of 2½ lbs. dry-powder type fire extinguisher, full charged with a gauge, in working condition and convenient to the operator.
  10. All drivers must wear helmets that meet or exceed Snell 2000 rating or must meet SFI specification 41.2. No modifications or alterations of the helmet are allowed. All chinstraps must be fastened. Helmets with fire retardant lining and a flame retardant neck shirt allowed. If you use a helmet with a fire retardant lining and flame retardant neck skirt, no head sock is required. Once a helmet has suffered a severe impact, it must be replaced or sent to manufacturer for re-inspection.

Tires

  1. Tires maximum 31.5 x 15 x 15 terra tires or bar tires. No duals, chains allowed. Uncut D.O.T. legal tires may run in this class max. 16.5 x 12.5 x 35. Outside corner to outside corner tread (measure).

Weights

  1. Maximum weight for truck and driver is 6200 lbs.

All general rules apply where applicable.