A- Modified

2025 A-MOD RULES

NO CARBON FIBER. NO TITANIUM UNLESS OTHERWISE NOTED. NO BUMP STOPS. NO BUMP SPRINGS OR CHASSIS LIMITERS. NO TRACTION CONTROL DEVICE(S) OF ANY KIND.

CAR:
American made, factory production, 1970 or newer with parallel frame, rear wheel drive only. Minimum wheelbase 108”. Wheel base must be within 1” side to side.
WEIGHT: (Weight and left side percentage can be checked at ANY time before, during or after time trials and or racing events with the driver sitting in the normal driving position with helmet and fire suit.)
1. Minimum weight 2650 lbs.
2. 58% left side.
3. Tube clip cars must have 50 lbs in front of the flywheel of existing weight total.
4. VORTEC heads must add 50 lbs.
5. Must add 50 lbs for any clutch under 10″
CHASSIS:
1. OEM stock for chassis clips or fabricated / tubular frames (must be approved by tech.)
2. Frames may not be widened or narrowed and must be able to support roll cage on both sides. Front cross members may be notched for radiator clearance only. No widening or fabricating of cross members. Must maintain stock measurement from cross member to A frame bolts.
3. Ride height minimum of 4” to body, frame and lead at all times. No pulling up on the car in the tech line.
4. MODIFIED TUBE CLIP. Must use stock lower A-Frames, steering box and idler arm. Must maintain 3-¼” from lower control arm bolts to bottom of cross member at all times. Lower mounts must be solid and non-adjustable. Must measure 17” – 1/4” tolerance from center bolt to center bolt on front side of lower control arm and 27” – ¼” tolerance. Any tube clip that doesn’t meet the specs will be deemed illegal.
6. Adjustable Idler arm allowed but MUST be mounted in stock location.
BODY:
1. Width 66 inches maximum length 120 inches maximum measured from front of door / back of engine block to the end of rear quarter at any point. 6” maximum body rake. Maximum 3” at door and 3” at quarter to get the 6” total. Body must be mounted straight on the chassis.
2. Firewalls can be aluminum and floorboards are to be made of steel only.
3. Fiberglass, aluminum or steel duplicates of body parts are permitted.
4. Full roof is mandatory and must completely cover halo bar. Maximum of 21 inch drip rails allowed.
5. Original roof line of vehicle should be maintained with a maximum of 1” drop rear to front.
6. No wings, ledges or other ground effects anywhere inside or outside the car.
7. Rear spoiler allowed 6“ x 60“ only. B- post side panel must be 6” asay from spoiler and half the height of spoiler.
8. Engine compartment will remain open, no side panels. Hood sides may have a maximum of 6” drop and be enclosed at the rear of the hood. Bodies should extend no further than back of the block.
NOTE: (passenger side of body must be no further forward then the rear of the block).
9. Lower rear quarter panel turns not to exceed 1 inch maximum with a maximum of 2-1”braces/supports. Quarter panel minimum height from top to bottom in the rear is 18”
10. Windshield must cover at least the driver side 1/8” lexan only. Rear window optional. If used must be lexan. 1/8” lexan only.
11. Maximum front nose width 43 1/2”
CARBURETOR:
1. Built engines may run a stock Holley 4412 2-barrel (500 cfm) only or a 4-barrel Quadrajet carburetor.
2. Crate engines must run Quadra-Jet 4-barrel carburetor or 650 Holly (part# 80541-1) only. No modifications can be made except as specified. (If crate motor does not have GM or Ricky Brooks seals, you must run 2 barrel Holley and rules).
3. May remove choke plate and shaft.
4. NO Holley XP 2 Barrels.Must have a choke horn.
5. May change jets and power valves.
6. May use any adapter from carburetor to manifold – maximum thickness 1.625 inches including gaskets.
7. Two return springs mandatory
8. Billet metering block okay.
INTAKE:
1. Stock OEM cast iron. No porting, polishing or port matching.
2. May use Edelbrock RPM Performer – (General Motors 7101, 7104, 7116, 2101, 2116, 2701, 3701), (Ford 7121), (Mopar 7176).
3. General Motors 602 aluminum dual-plane intake manifold is also approved.
IGNITION:
1. Any 12-volt battery fired ignition (only).
2. Part # MSD8727 CT Digital Soft-Touch HEI Rev Control Limiter only (must be on the right hand side visible to tech out of reach of the driver).
3. Must be mounted in the driver’s compartment behind the driver’s seat. Must be mounted securely and in a box with a lid.
4. Stock distributor, aftermarket okay – no high-performance parts. No MSD coils or modules. Allstar #81202 allowed.
ENGINE SPECIFICATIONS:
1. Must be the same manufacturer as the car and mounted in stock position. May use aftermarket solid motor mounts. Must be in stock location!.
Maximum Cubic Inch: Displacement for General Motors – 350 C.I.D. / Ford – 351 C.I.D / Mopar – 360 C.I.D.
2. Stock crankshaft for engine (aftermarkets approved). No knife edge permitted. No polishing of crankshaft. 48 pounds minimum balancing permitted.
3. Maximum over-bore is .060.
4. Grinding on rods permitted for balancing only. Rods can be any 5.7 length. Rods, bolts, builders’ choice.
5. Any 3-ring flat top pistons, must use all 3 rings. Floating pins may be used.
6. May zero deck the block.
7. Any harmonic balancer – no aluminum
8. Painting or polishing lifter galley is okay. May block off center oil returns. Lifter tray okay.
9. Timing chain – engine builder’s choice, no gear to gear.
10. Rear of the engine (bell housing flange) must be mounted at least 72” forward from the centerline of the rear axle. Engine offset must be kept within the front stub. Engine offset maximum of 2” of centerline of front cross member. Crankshaft minimum height will be 11” from the ground to the center of the crankshaft. Must be wet sump only. No totally dry sump systems allowed. Wet systems must be operative.
GENERAL MOTORS (GM) 602 CRATE ENGINE:
1. Must be factory sealed or tech approved only.
2. May run GM 602 sealed crate engines that came from the factory. No modifications of any kind. Crate motors are subject to inspection at any time! Valve springs – Part# PAC1210X are allowed. May shim to get to spring rule.
3. 602 Crate engines must follow the Gm Performance parts Technical Manual. If it is not listed don’t do it unless you have spoken to tech and have your rule book signed and carry with you to tech. A tech bulletin will then follow for all racers to see the clarification or change.
4. 602 is totally by the GM manual, repairs etc. no exceptions
GM part number: 88958602 and 19258602
Compression ratio: 9-to-1.
No options allowed.
5. Part# MSD 8727CT Digital Soft-Touch HEI Rev Control Limiter only (must be mounted on the right hand side visible to tech out of reach of the driver).
CYLINDER HEADS:
1. Stock production OEM cast iron cylinder head for engine being used (Open or Closed Chamber Heads Okay Minimum 63CC)
2. World Product #043610 or Dart #10024361 heads are allowed. VORTEC-style heads allowed (MUST ADD 50 LBS).
3. No titanium parts allowed.
4. GM 350 heads on 350 c.i.d. engine – 305 heads on 305 c.i.d. engine no less than 63 cc’s on 350.
5. Ford 351 heads on 351 c.i.d. engine – 302 heads on 302 c.i.d. engine. Maximum compressions ratio: 10-to-1.
6. Mopar 360 heads on 360 c.i.d. engine – 318 heads on 318 c.i.d. engine: Maximum compression ratio: 10-to-1.
7. No porting or polishing, no gasket matching, no grinding of any kind.
8. May have 3 angle valve jobs, no angle more than 75 degree. May run screw in studs, must be stock size.
9. Guide plates OK.
10. No angle plug heads.
11. Must use stock diameter valve for head used.
12. 1.94 intake, 1.50 exhaust, max valve size. May be stainless steel, neck down valves okay.
13. No hollow stem valves.
14. Valve spring must be stock size and symmetrical from top to bottom (1.270” max diameter). Spring seat valve pressure closed 120lbs. max.
15. Bronze guides or liners ok.
16. Push rods, builder’s option.
CAMSHAFT:
1. Hydraulic flat tappet cam only.
2. Maximum lift 450 at the valve for GM.
3. Maximum lift 480 at the valve for Ford.
4. Check at push rod or cam lobe times the rocker.
5. Ratio – Rocker must remain stock for engine: General Motors: 1.5 – Ford: 1.6 – Mopar: 1.5.
TRANSMISSION:
1. Saginaw 3 speed or 4 speed, Muncie four-speed and turbo 350-400 automatic transmission with two forward and one reverse gear allowed. 10” inch minimum torque converters. No lock up converters. No five speed transmissions, No in/out boxes. No buttons or couplers. Must all be clutch operated with motor running and car still in position. Driver must be able to engage the car in gear and move forward, then backward at time of inspection. Clutch must be inside the bell housing. Must have all gears working and reverse. No light weight parts or straight cut gears.
2. Clutch size minimum 5 1/2 inches. Must add 50 lbs for any clutch smaller than 10” inches.
3. Stock OEM transmissions allowed, Power glide transmission allowed. NO RACING TRANNY’S ALLOWED.
4. L88 flywheel OK 14 lb minimum
DIFFERENTIAL:
1. 9 inch floater or quick change. 10 or 12 bolt
2. Wide 5 hubs allowed with bolt on front adapters to stock spindle, stock lowers only. Must remain in the factory location.
3. No rear sway bar.
WHEELS & TIRES:
1. Racing wheels 15” x 8”. May run any combination of 2,3, or 4” offset wheels .
2. American Racer AR870 Tires (only).
3. No bleeders
ROLL CAGE:
1. Must consist of continuous hoops, not less than 1-¾” outside diameter must have a wall thickness of at least .095.
2. Must be frame mounted in at least 6 places.
3. Must consist of configuration of front and rear hoops connected by tubing on the sides or side hoops. Drivers heads must not protrude above the cage with helmet on and strapped in the driver seat. Roll cage must be securely supported and braced.
4. Protection of feet is mandatory. Bar across the back of the engine with vertical bars and rub rails or similar protection.
5. No brace bars forward of the cage may be higher than stock hood height.
6. Driver door bars must be as parallel with the ground as possible and located perpendicular to the driver so as to provide maximum protection for the driver without undue difficulty in getting into or out of the vehicle. Sidebars must be welded to the front and rear of metal cage members. Door bars less than .095” thickness should have 4 bars at least 1-1/2” diameter. Must have steel plate covering the driver’s door area.
7. Must have a five point harness with date specifications.
8. Window nets Mandatory
BUMPERS:
1. Must be used in both front and rear. Front bumper should be mounted frame end to frame end with bottom loop parallel to the ground. Should be made of 1-1/4” pipe and must be welded to support the car if lifted by a wrecker.
2. Rear bumpers, nerf bars, and bodies must not extend beyond width of the rear tires and must not contain any sharp edges.
3. Rear bumpers may be constructed of pipe, flat stock or Aluminum I-beam and must protect the fuel cell. Center bumpers front and rear must be 18” (plus or minus 2” from ground.
FUEL CELL:
1. Maximum of 22 gallon fuel cell mandatory. Cutting of trunk for the fuel cell is permitted. Fuel cell must be in 22” gauge steel.
2. Sunoco spec. fuel only – NO additives allowed
DRIVE SHAFT:
1. Must be a steel driveshaft ONLY. NO aluminum or carbon fiber
SUSPENSION:
1. Stock passenger car spindles only. No fabricated spindles. Center of ball joint to center of tie rod must be stock measurement as well as the same measurement on both sides.
2. OEM Bottom A-frames cannot be moved. Ford lowers are allowed as long as they are in stock mounts.
3. One piece OEM or aftermarket sway bar only.
4. No coil over shocks (front or rear). Coil over eliminators must be used in the rear only with a minimum spring diameter of 4-1/2”.
5. No fiberglass springs allowed. No torsion bars allowed in the rear.
6. No hydraulic. Ratchet or electric weight jacks anywhere in or around the car.
7. One shock per wheel only. Steel non adjustable and non-rebuildable shock only. No Schrader valves. Adjustable shafts and canisters are not permitted. No Aluminum shocks permitted. No split valving, must be the same up and down. ($150 claim rule per shock). Shocks Must Be Straight up 3 to straight up 7 ONLY Meaning 3 up 3 down, 7 up 7 down NO Gas shocks. Recommended shocks:
Front: Pro WB74BK. Pro WB75BK, Pro WB 76BK
Rear: Pro WB93BK, Pro WB94BK, Pro WB95BK
8. Heim joints on inner and outer tie rod okay. No racks.
9. Front rotors may be re-drilled for larger studs or different lug patterns but may not be lightened.
10. Front Coil Springs will be 500 lb minimum. No exceptions.
11. No lift bars allowed. No exceptions
12. One spring rubber per spring is allowed.
COMMUNICATIONS:
1. Raceceivers required.
2. Radios and spotters allowed
BRAKES:
1. Brakes must lock up all 4 wheels during post inspection. All 4 brakes must work.
2. Front and rear brakes must consist of stock appearing components single piston only.( Aluminum ok)
3. May run steel or aluminum front safety hubs. May run after-market rear hats and rotors
4. Brake Bias ok to run.
EXHAUST:
1. Exhaust system must be mounted in such a way to direct spent fumes away from the cockpit of vehicle and must extend past frame rails and away from all areas of possible fuel spillage. All headers are allowed.

Refer to General Rules for Protest fees.
Refer to the General & safety rules for more information and requirements

Updated: January 11, 2025
Effective: January 11, 2025