Southern Lightning Modified Rules

Southern Lightning Modified Rules


  1. BODIES 1.1.All bodies must be 1980 or newer replicas of American passenger cars only. Steel, fiberglass, or aluminum full-size roof required. No wings allowed. No stock bodies. Bodies must be neat in appearance and in good condition.

1.2.Firewall and floorboards are mandatory.

1.3.Bodies will conform to the following measurements: window openings must maintain 18-inches maximum forward/aft and 12-inches minimum tall on both sides.

1.3.1.Rear body height of 38-inches maximum with an additional 5-inch maximum spoiler permitted for an overall rear maximum height of 43-inches from the ground to the top of the spoiler.

1.3.2.Rear body width between 66-inches maximum and 53-inches minimum. Must be the same front to back.

1.3.3.Center of the rear spindle to the rear of the body must be between 48-inches maximum and 34-inches minimum.

1.3.4.Center of the front spindle to the front of the body must be 42-inches maximum.

1.3.5.A maximum slope of 6-inches will be permitted from front to rear measured on both sides starting at the leading edge of the door panel measured at or near the Apost to the rear edge of the quarter panel. Slop must be maintained from door to rear.

1.3.6.No additional panels or fillers may be added.

1.3.7.No additional air deflection panels may be added in any area of the car. Examples include but are not limited to the front, rear body or nose, alongside the engine compartment and inside the exterior body.

1.3.8.Bodies must have a solid panel at least eight (8) inches minimum and 22-inches maximum in height and must extend completely across the rear of the car. No open rear bodies allowed. Spoiler is to be no wider than the width of the rear body and a maximum 5-inches high.

1.3.9.Hood must be level or sloped down at front, enclosed and a maximum two (2) inches above interior deck at rear. No reverse hood rake allowed. A 6-inch maximum scoop cannot extend past front of hood.

1.3-10 Engine compartment sides must remain open. Hood sides may have maximum of four (4) inch drop and must be enclosed at rear of hood.

1.3-11 Front windshields must be complete from dash to roof, a minimum of 14-inches wide, constructed of 3/16” Lexan. The windshield must not extend beyond the centerline of car or above roof line. Full Lexan windshields and rear windows are allowed if the front and rear of the Greenhouse is manufactured to accommodate these windows, such as the MD3 Asphalt Modified body Greenhouse. Braces are required to support the Lexan windshield.

1.3-12 Front body nose height is a minimum of four (4) inches.

1.3-13 All Modified cars will be numbered with large legible numbers on sides of both doors and on top of roof. Numbers on sides of car should be in contrasting color to body. Numbers must be at least 20-inches high and at least four (4) inches wide. Roof numbers will be placed with the top of number toward the drivers’ side of car (to be read by flagman). Roof number must be at least 24-inches high and at least four (4) inches wide.

1.3-14 All Modified cars will have their car number at least four (4) inches high displayed on the right front nose and on the right rear panel. 9. Decals must not interfere with the car numbers. All cars must display divisional sponsor decal.


2.1.All cars must use factory production American passenger car front frame sections. Frame sections cannot be narrowed or widened. The 1968-72 GM Chevelle OEM or OEM replacement frame has been approved.

2.2.Steering: No rack and pinion. Tie rod sleeves and rear end alignment tubes will be made of steel. The tie rod tubes outer tie rod ends may be replaced with Heim joints to correct bump steer. Upper link may be aluminum. Any type of front sway bar is permitted, but arms on aftermarket bars must be made of steel.

2.3.Spindles may be either OEM or Howe aftermarket stock replacement spindles, part # 344GN (right side), part # 344GNL (left side) and the Howe replacement with the IMCA raised stamp. Weld-on brake brackets and aftermarket steel hubs are permitted. No other modifications allowed. Spindles must remain stock and holes must remain in stock location.

2.4.Steel steering shafts and knuckles only. Driver compartment steering may be modified but must be kept on the left side. Quick release required, steering quickener and steering wheel may be aluminum.

2.5.Any type of rear suspension is permitted. All springs must be a minimum of 4½ – inches in diameter. Coil-over springs are not permitted on the front but are permitted on the rear. No torsion bar rear suspensions permitted. No independent rear suspensions allowed. The top link spring does not apply to the 4½ -inch diameter rule.

2.6.No aluminum except for pan-hard bar. Upper link may be aluminum. Any type of front sway bar is permitted but arms on aftermarket sway bars must be made of steel.

2.7.Any type of shock is allowed. External adjustments will not be permitted with the exception of Schrader valves. Shock absorber base valves will not be permitted. Remote or electronically controlled shock absorbers will not be permitted.

2.8.Front suspension: All components must be steel. Lower A-arms may be OEM or aftermarket and be mounted in stock location. A-arm bushings made of steel or spherical bearings are permitted. Tubular upper A-arms and aftermarket mount plates made of magnetic steel are permitted. OEM or OEM replacement ball joints allowed. Lower A-frames must be the same right and left, and of the same design.

2.9.Wheelbase must be a minimum of 108-inches.

2.10.Maximum tread width of car (both front and rear) must not exceed 78-inches, as measured outside of tire to outside of tire at spindle height.

2.11.Frame, nose and body height will be a minimum of four (4) inches at all times, with driver in the car.

  1. ROLL CAGES 3.1.Roll bars must consist of continuous loops not less than 1.750-inch outside diameter and must have a minimum wall thickness of .095-inch.

3.2.Roll bars must be frame mounted in at least eight (8) places.

3.3.Drivers’ head must not extend above roof loop with helmet on and strapped in car.

3.4.Foot protection consisting of bar or plate is mandatory.

3.5.Driver door bars must be parallel with the ground and located to provide the maximum protection for the driver. The side bars must be welded to the front and rear of the roll cage members. Door bars must have a minimum wall thickness of . 095-inch. A minimum of three (3) bars at 1.750-inch outside diameter or four (4) bars at 1.50-inch outside diameter must be used.

3.6.A .090-inch minimum wall thickness magnetic steel plate attached to the drivers’ side door bars is required.


4.1.All cars must weigh a minimum of 2,600 pounds with driver at all times. Driver’s side of car cannot exceed 58% of total weight of car. No fluids may be added to maintain weight after the completion of an event for post-race inspections.

4.2.Added weight must be in block form of no less than five (5) pound blocks. NO PELLETS will be permitted. Added weight must be securely bolted in place and painted white with car number on it. Any dislodged weight will not be returned to the car for weighing after race.


5.1.Steel bumpers must be on front and rear at all times and welded, or mounted with minimum 0.375-inch bolts. Rear bumper must be constructed of solid square, or minimum1.25-inch outside diameter tubing with minimum 0.095-inch wall thickness, maximum six (6) inches beyond rear deck, no wider than five (5) inches outside of rear frame rails. If wider than five (5) inches outside of rear frame rails, must be capped and bent forward 90 degrees, or constructed in a loop design. Must have at least one upright, minimum 1.25-inch outside diameter with minimum 0.065- inch wall thickness, from bumper to fuel cell guard. Two-bar front bumper must be minimum 1.25-inch outside diameter tubing with minimum 0.065-inch wall thickness (maximum 0.095-inch) mounted frame end to frame end, no wider than width of material outside frame horns and with bottom loop parallel to ground. Top bar must be directly above bottom bar, minimum 6.5-inches apart, measured center to center.

5.2.Center of bumpers must be eighteen (18) inches above the ground, plus or minus two (2) inches.

5.3.Nerf bars must extend between one (1) inch, plus or minus, to outside edge of the tires. Rear nerf bars are strongly recommended.


6.1.Any steel approved OEM passenger car or truck rear end (housing or carrier) allowed. Quick change rear ends are permitted with steel axle tubes only. Only Detroit locker ratchet type differentials will be permitted. When this type of differential is used, either wheel, when jacked up with the transmission engaged, must turn freely by hand for one (1) full turn, 360 degrees, while the opposite wheel remains stationary. Locked rear drive axle assemblies (solid spool) will be permitted. When jacked up, both rear wheels must rotate in the same direction and the same rotational distance at all times. One (1) wheel, when jacked up must not rotate in any direction. No torque dividing differentials. No scalloped ring gears. Hubs and all other rear end components must be made of steel. However, axle caps, lowering blocks, drive plates and carriers may be aluminum. Rear ends may be cambered plus or minus one (1) degree only. No electronic traction control devices permitted.


7.1.Only single piston OEM or aftermarket brake calipers that conform to OEM specifications accepted. Brakes must be fully operational on all four wheels and must lock up on inspection. Absolutely no electronic or hydraulic traction control devices allowed on brakes.


8.1.Each car is allowed only one (1) 12-volt battery. Batteries must be securely mounted and shielded.

8.2.All cars must have an electrical cut-off switch mounted in the center of the car or in the center of the dash. This switch must be labeled ON and OFF.

8.3.All cars must be equipped with a self-starter.

8.4.4 Alternators may be used.

8.5.No electronic traction control, timing devices, rev-limiters are permitted on race cars at any time.

8.6.Transponders All transponders shall be mounted 72 inches, plus or minus 2 inches from the edge of the front bumper, measured from the center of the car.

  1. ENGINE 9.1.Any American production passenger car engine is allowed.

9.2.Mounting locations on block cannot be altered from OEM, i.e., frame mounts, starter, fuel pump, etc.

9.3.Engine must be mounted at least 72-inches forward from the centerline of the rear axle housing, measuring to the bell-housing flange at the rear of the block. The distance from the center of the crank to the ground can be no lower than 11-inches. Engine must be mounted between the front frame rails.

9.4.Exhaust system must include muffler and must exit behind the driver. Free flow mufflers are allowed. Cars must not exceed a 99-db level, as measured by track officials. Sound levels may be monitored anytime cars are on track. Cars determined to exceed track noise limits will be required to modify the exhaust to reduce noise to acceptable levels.

9.5.High Energy Ignition (HEI) with four (4) prong module or MSD #8364 replacement module is allowed. The MSD distributor allowed for a Chevrolet is #8365. No magnetos, forced air induction, dry sump systems or electric fuel pumps allowed. No timing retard components allowed. No cutting or splicing of any of the distributor wires allowed. All components and wires must remain in their original factory configuration. At any time, you may be required to change the distributor module or detach the tachometer wire from the distributor. Point distributors are allowed.

9.6.Carburetor must be a Holley 500 cfm 2-bbl the Holley Ultra will not be permitted. The maximum butterfly and venturi diameter is 1.750-inches. No sleeving of venturi or booster modifications allowed. Any intake may be used, either two or four barrel with adapter or spacer, except tunnel rams. No air leaks in the manifold, spacers or adapters below the venturis.

9.7.Cars must race with the carburetor used in qualifying.

9.8.No aluminum cylinder heads or aluminum engine blocks.


10.1.Competitors must notify the Technical Director when using a crate engine.

10.2.The GM sealed crate motor part number 88958602, (350 ci/350 hp), is the only crate engine allowed.

10.3.The Holley 650 cfm 4-bbl carburetor, part number 4777.C or 80541-1, is approved for use on crate motor only. Removal of choke is allowed. No other alterations will be allowed. Only one (1) non-adjustable one-piece solid aluminum spacer permitted, maximum one (1) inch in height with one (1) gasket per side not to exceed .065-inch in thickness. Openings of spacer must be cut perpendicular, matching carburetor base and no larger than the base of the carburetor. No tapering or beveling permitted.

10.4.Car must weigh a minimum of 2,450 pounds at all times with driver. Left side weight cannot exceed 58% of total weight of car.

10.5.Engine must be mounted at least 72-inches forward from the centerline of the rear axle housing, measuring to the bell-housing flange at the rear of the block. The distance from the center of the crank to the ground can be no lower than 11-inches. Engine must be mounted between the front frame rails.

10.6.No aluminum cylinder heads or aluminum engine blocks.


11.1.Only OEM-type transmissions allowed, 3-speed, 4-speed or automatic. No 5- speeds, in/out boxes, overdrives, couplers, or buttons allowed. All cars must have an operable reverse gear and be able to back up and move forward from standing position.

11.2.Clutch-type transmissions must be equipped with approved blow-proof bell housing. A transmission blow-proof cover shield is required for automatic transmission cars.

11.3.All flex plates must be OEM or SFI-approved. No FFI or other manufacturer of flex plates allowed.

11.4.Only steel drive shafts are permitted. Drive shaft must be painted white and have car number on it. Car must be equipped with a drive shaft strap made of steel that is a minimum 3/16-inch thick by a minimum 2-inches wide.


12.1. 8-inch steel wheels are allowed 10-inch wheels will be permitted but will carry a 1% left side penalty (Max 57%)

12.3.All cars must start the feature race with the same tires on which the car qualified.


13.1.Racing fuel cells are required. Maximum capacity of fuel cell is 22 gallons. Minimum clearance from ground to lowest point of fuel cell is eight (8) inches. The fuel cell must be enclosed in a metal container constructed of a minimum of 22- gauge steel. It must be securely mounted in race car with at least two (2) straps widthwise. Straps must be made of steel, a minimum of 1/8-inch thick by a minimum of one (1) inch wide.

13.2.All fuel cells must have a closed cap or check valves on gas fill and vent. Fuel cell vent must exit on outside of rear panel, approximately 12 to 18-inches from the left side of quarter panel.

13.3.It is recommended that fuel cell foam be changed every three (3) years.


14.1.All drivers must wear a helmet that is Snell SA 2000 or Snell SA 2005. All helmets must be inspected by the Technical Director. Helmet must accompany car at time of inspection.

14.2.All drivers must wear fire suits made of flame-retardant material. Suits must be kept in presentable condition.

14.3.All drivers must wear flame-retardant gloves. Flame-retardant hood, socks and shoes are highly recommended. Gloves and other safety equipment covered with grease and/or motor oil and not properly cared for should be replaced.

14.4.The driver’s competition harness and lap belt must be at least three (3) inches wide with a submarine strap. Metal to metal buckles are required on shoulder and seat belts. The shoulder harness should be mounted even with or slightly higher than driver’s shoulders. Belts that are weathered or frayed will not be permitted for racing use.

14.5.Approved HANS-type head and neck restraint is mandatory.

14.6.Fireproof driver’s side window net is mandatory and will not be accepted if cut, tattered or frayed.

14.7.All cars must be equipped with an on-board fire system/extinguisher that is fully charged and accessible to the belted driver.

14.8.All roll bars within the drivers reach of his/her leg or arm must be padded with an acceptable padding.

14.9.The steering wheel must have a safety pad in the center.