2021 Motor City Muscle Challenge N/A 9″ Rules:
Naturally Aspirated – All Motor -1/4 Mile – .400 Pro Tree – 16 Car Qualified Field – Pro Ladder
Rules are subject to change at any time and all final decisions are to be made by the Race Director.
Sponsored By:
Base Weights
Small Block Chevy, Ford, Mopar minimum weight 3000 pounds with a maximum Cubic Inch of 440.
Big Block Chevy, Ford, Mopar minimum weight 3300 pounds with a maximum Cubic Inch of 565.
Engine must be a corporate engine to corporate body match. (i.e. – Ford/Ford, GM/GM, Mopar/Mopar)
Stock bore space blocks only – No billet blocks.
All Motors will be pumped (P/G) for compliance and sealed at indiscriminate times at any race.
Any time a seal is broken, engine will be required for re-pumped and reseal.
Any infraction (CHEATING) can or will result in immediate disqualification from series.
Heads
OEM STYLE means standard port and valve layout front to rear, and port height within reason of understanding what commercially is available for conventional heads. (No billet heads) This definition will be subjective under MOTORCITY MUSCLE CHALLENGE N/A 9″ tech discretion.
Big Block Chevy, Mopar, Ford Conventional OEM style heads. Minimum weight of 3300 pounds. No billet heads – No hybrid OEM Style racing heads – No BBC SR20, 23BBC heads, BBF C Port, only normal conventional aftermarket heads such as those from Brodix, Dart, BMF, AFR, B1, Indy, TFS etc. allowed. No intake port height limitations.
Big Block Buick, Oldsmobile & Pontiac Conventional OEM style heads. No billet heads – No hybrid OEM Style racing heads.
Tech will use discretion when considering legality of heads presented to advisory board.
Small Block Chevy, Mopar, Ford Conventional layout, in-line valve style heads. Minimum weight 3000 pounds. No port height limitations. Non inline cylinder heads such as SB2, Yates Style, may run with 75 lb. penalty. (No billet heads)
LS Based Engines – In-line heads allowed at base weight. MAST STR8 Jacket and CID BE-LS inline heads add 75 lbs. Other similar style heads not specified here will be considered on a case-by-case basis.
Canted and/or splayed valve heads such as Mast Mozez or Edelbrock LS-R heads – add 125lbs. (No billet heads)
Carburetors
Any commercially available 4150 style 1.75″ throttle blade 4 bbl. single carburetor allowed. Must mount on to a 4150 bolt pattern. (4500 to 4150 adapter permitted) (Dominators or Dominator style carburetors prohibited)
Fuel injection
No fuel injection allowed
Oiling System
Wet or dry sump systems allowed
Intake Manifolds
Any COTS (commercial off the shelf) commercially, “out of the box, bolt on” cast aluminum intake manifold allowed. No external modifications, no custom, “one off” manufactured, no cast blank intake machined and modified to fit, no cutting and welding runners and/or mounting flanges, no re-drilling flange (bolt holes must remain as machined in COTS production) and manifolds must have manufacturers part number identification visible as provided by manufacturer when new.
Any design allowed but must fit under the hood.
No tunnel rams or bolt together style intake manifolds allowed – NO EXCEPTIONS! (This includes top to base or side to side).
No intake spacers of any kind allowed – intake must bolt directly to cylinder heads. (All reviewed at technical advisor’s discretion*)
Transmissions
Auto Transmissions: Any auto trans allowed. Adapters are permitted. Trans brakes permitted.
Automatic transmission entries run at listed base weights. Pneumatic, electric, hydraulic, etc. shifters prohibited. Any gear change must occur from direct action by the driver. No lockup converters.
Manual Transmissions: Any style manual transmission allowed. No limits on clutch style. 75 lbs. added.
Body
Stock steel fenders, steel doors, steel trunk lid. (Magnets will be present)
Stock located factory steel firewall and factory steel floor pan are required.
Stock appearing interior (door panels, dash, carpeting is required from seats forward)
Factory appearing rear spoilers allowed. (Rear Wings allowed)
Fiberglass bumpers allowed.
Fiberglass hoods allowed
Front Light Tripper or Extenders prohibited
Pro Glass – Optic Armor type glass is permitted provided it is attached and installed (butyl, glue etc.) as OEM size and style glass with the OEM fashioned trim. No nuts, bolts, screws, rivets etc. allowed. Must appear as Factory or OEM by tech directors.
Hood
Limited to 6″ cowl style hood. (+/- ½”) No forward cut outs in hood permitted.
The 6-inch maximum means anywhere along the cowl scoop profile, measured against the primary surface of the hood.
No single point of the cowl allowed to measure more than 6″.
No aftermarket forward facing hood scoops.
No restrictions on air intake position. i.e. under the car, grill area, windshield, etc.
Frame
Stock located unaltered frame rails required front sub-frame from suspension points rearward. Sub-frames on uni-body cars may be joined under car. Factory located rear frame rails may be mini-tubbed provided inner frame rails remain in stock location. Modifications allowed for clearance only.
All vehicles must have a chassis certification that meets guidelines set by SFI for their respective speed and elapsed time.
Rear Suspension
Stock Leaf Spring or Stock Coil Suspension, Coil over shocks allowed.
Traction Bars, Cal Tracs, Slide–a–Link or Torque Arms are permitted.
Ladder Bars
Bolt in or weld in anti-roll bars allowed.
No 4-Links allowed
Wheelie Bars Prohibited
Front Suspension
Front suspension must represent the “stock type” suspension for the model car being used.
“Stock Type” refers to any custom parts used, must mount directly to stock suspension points.
Cars originally equipped with A-Arms must continue to use A-Arms on the stock mounting points.
Aftermarket A-Arms which are adjustable are acceptable.
Cars equipped with Struts, must utilize struts in the original strut towers. Manipulation for proper geometry within the tower is acceptable.
Bolt on K-Member style cradles for late model cars are acceptable but must follow the Strut and A-Arm rules. Coil over front shocks allowed.
No Spindle mount wheels.
Rear Tires
Tires limited to 9×26, 9×28, 9×29, 9×29.5 or 9×30 slicks only. (Radial sidewalls permitted)
9″ maximum tread width. Go-No gauge will be used for measuring.
Use of any traction control device is prohibited
Lower Engine Containment Device or Diaper Required.
Oil Retention Device:
Diaper Device may be custom-built ballistic blanket-style (Diapers: they do not have to be SFI rated.)
Metal bucket device or metal pan may be no longer than the engine from the front of crankshaft to the rear of the flywheel.
Pan must be inside the frame rails and fabricated to retain oil\liquid.
Pan must attach to the frame via conventional fasteners or straps.
Pan must be a minimum of 3 inches above ground.
*Any infraction (CHEATING) could potentially result in disqualification from series per rules board*
ALL CARS MUST MEET ALL IHRA or NHRA RULES INCLUDING LICENSE AND CERTIFICATION
*All Rules Are Subject to Change