B-Mod Rules


2021 B-Mod Rules

Chassis and Frame

A. 1964 or newer OEM perimeter American rear-wheeled passenger car frame only. No sports car frame. No convertible or station wagon. No stub cars

B. Frame must be full and complete, cannot be widened or narrowed and must be able to support roll cage on both sides. Exceptions are weight jack in original line of spring tower, frame may be cut a max of36 inches forward from center of rear end housing. Horns may be removed in front of steerin box and notched maximum of1 inch at bottom for tie rod clearance. Maximum 7 inch wide opening in side of spring tower for spring removal.

C. All cars must have box type roll cage of at least 1.5” O.D tubing .095 minimum thickness. All cars must be equipped with a minimum of three protective bars inside each door. Halo loop MUST be a SINGLE bar.

D. Must have loop to protect fuel cell.

E. Minimum wheelbase 108” maximum 112” both sides.

F. No part of car can be lower than 4 inches from ground except front cross member

G. Floorboard must be steel or 16 gauge aluminum

H. Drivers windshield opening must have a minimum of3 upright bars of 3/8” gauge steel rod welded to roll cage in front of driver 6” apart. Windshield opening covered by wire mesh is strongly recommended. Doo window openings must be minimum of 12”

I. Must run modified style bumper, all bumpers must be securely bolted or welded. All bumpers and nerf bar ends must be capped, door nerf bars 1.25” max tubing.


1.1 – Suspension

A. Any “live axle”-type rear ends will not be permitted.

B. Quick change rear ends will be permitted. No lightened, 8″ or midget rear ends allowed. Only magnetic

axle steel tubes will be permitted.

C. Aluminum spools will be permitted. Aluminum 3rd members will not.

D. Aluminum birdcages will not be permitted. Aluminum third members will not be permitted.

E. Independent rear suspensions will not be permitted.

F. Only floater hub assemblies will be permitted.

G. The front suspension must be O.E.M. and be in stock location. The front suspension must have replaceable stock part(s) from the same type of suspension.

H. Only stock passenger car spindles will be permitted. Fabricated spindles will not be permitted.

I. Alterations and/or relocation of the lower A-frames will not be permitted. Only control arms which are mounted in the OEM location will be permitted. Tubular and/or specifically fabricated after-market lower control arms of stock dimensions will be permitted.

a. Control arms are subject to a $10 inspection claim.

b. Illegal control arms will be forfeited to official and returned at end of season.

J. Tubular-type upper A-frames will be permitted. The upper A-frame mounting locations may be altered.

Upper control arm must be mounted on top of frame rail. Aluminum cross shafts will be permitted

Rear Suspension

A.  All components must be steel. Covers of any-type will not be permitted. All rear suspension mounts and brackets must be welded or bolted solid. All springs must be a minimum of 5″.

B. Coil springs must remain vertical. Springs must be mounted to the rear end housing. The spring location may be on top, to the rear or to the front of the housing. Springs can be mounted in staggered locations on the rear end housing.

C. Coil-over eliminators utilizing a minimum spring diameter of 5.00″-inches will be permitted.

D. Chains, Cables, and/or tethers to limit or control movement will be permitted.(shocks and/or dampeners not permitted).

E. Rear shock absorbers mounted on the control arms will not be permitted.

F. All rear control arms and panhard bars must be straight and J Bars connected end-to-end using a solid mounting system on either end. Only one of the following designs will be permitted for competition;

a. A three (3) link design will be permitted with the following requirements. The lower control arms must maintain a maximum length of 24″-inches and a minimum length of 15″-inches. The one (1) upper control arm must be a solid tube located at the top center of the rear end housing and remain centered (one -inch tolerance) over the housing and/or top of the drive shaft. One panhard bar, a minimum of 23″-inches in length can be mounted behind the rear end housing. A J-Bar will be permitted. The lower spring perch must be welded or bolted solid to the rear end housing. The bottom of the rear spring(s) must remain within 2 3⁄4-inch of the axle tube(s). Only steel upper weight jack(s) will be permitted. Floating and/or bearing rear spring perches/cups will not be permitted. Suspension stops of any type will not be permitted.

b. OEM stock design suspensions will be permitted with the following requirements. The rear cross member and control arm mounts and bolt holes on frame must remain the stock OEM location. All components must be unaltered, approved OEM and match frame. The control arms must not be altered. Only steel, rubber or nylon control arm bushings will be permitted. The rear springs must remain in the stock OEM location. The lower spring perch must be welded to the rear end housing. Only upper weight jacks made of magnetic steel wheel be permitted.

G. Leaf spring stacked steel are permitted. Composite material springs are not permitted. Mono leaf springs are not permitted.

H. In the rear of the car a minimum 5″-inch spring is required.

I. All springs must have a tethered and/or cable system in place to securely fasten them in position in the car.

J. Aluminum shocks, shells, aluminum hubs, aluminum A-frames, aluminum rear-end, aluminum tubes and/or other aluminum suspension parts will not be permitted.

K. Coil over shocks of any type on the front of the car will not be permitted.

L. Coil over shocks optional on rear end of car with 5″ springs only.

M. Only one shock per wheel will be permitted. Lay down shocks less than 12″ (twelve inches) away from brake rotor will not be permitted. Additional shocks in other locations will be permitted.

N. One steel, non-adjustable, unaltered shock per wheel only. All shocks must completely Collapse at any time. No external or internal bumpers or stops. No bulb-type, threaded body, AGR, or remote reservoir shocks. No Schrader valves or bladder type valve allowed. Rules committee reserves the right to allow or disallow any shocks at their discretion. It is the responsibility of the racer to receive approval for any questionable shock used in competition

O. Shock Claim RULE $50.00 per shock. Driver, car owner and/or Promoter race series can claim shock. Driver/Owner must finish in top 5 of race that shock is being claimed in. If shock is found legal, Protested driver is awarded the $50 protest fee and their shock is returned. If shock is found illegal, shock is forfeited to track for the rest of the season and protester is returned their money. At the end of the season, shock is returned to owner for disposal/resale.


A. All cars must be equipped with a working braking system on all four wheels and all four wheels must be able to stop/brake all times.

B. Only magnetic steel rotors will be permitted. Carbon fiber and/or aluminum rotors will not be permitted. Drilling, lightening and/or any alteration to the brake rotors or calipers will not be permitted.

C. Only stock O.E.M. type rotors will be permitted. Single disc brake rotors or scalloped rotors will not be permitted. Floating brake systems of any type will not be permitted.


Open Motor

A. Steel engine block, steel heads, No 400c.i blocks. 3.48 stroke and standard stock journal size only. Aftermarket steel or stock steel heads allowed, no aluminum heads, must be stock valve angle Chevy 23* Ford 22*

B. Chevrolet, Ford, and Dodge OEM Engines ONLY. Aftermarket blocks will not be permitted. A maximum of 360 cubic inches will be permitted for any steel engine.

C. The “Steel Block/Steel Cylinder Head” engine may only use one 500 CFM 4412 Holley unaltered carburetor. The local track rules reserve the right for carburetors to be claimed and/or changed {i.e. “exchanged”) for competitive analysis and/or inspection. Choke horns may be removed.

D. Only flat tappet type cams and lifters will be permitted. Roller rocker arms and stud girdles allowed. Shaft Rockers will NOT be permitted.

602 Crate Engine

A. The Chevrolet Performance Parts 602 engines {GM Part Numbers 19258602 – 88958602) will be permitted. The engine and all components must remain in their original configuration and form as purchased and/or delivered by GM. Any alterations to the engine will not be permitted. The engine must remain as manufactured by General Motors Performance Parts 602 crate engines may have part number changes from time-to-time as issued by the manufacturer. All engines must retain all GM Factory seals. Tampering, removal, or modifications of any type and/or broken factory seals will not be permitted.

B. In addition, Only Chevrolet Performance replacement parts of any type will be permitted for any type of replacement and or repair work. Only Chevrolet Performance Engine specific valve springs may be used for replacement or repair. Part numbers 10212811 or 19154761 must be used. Approved repair is permitted; however, engine rebuilds are not permitted.

C. Any 602 engine that has non-conforming or missing seals will be disallowed and Illegal engine.

D. A Chevrolet Performance 602 engine without full seals will be considered an open engine.

Chevrolet Performance 602 Engine or Optional Engine Distributor / Ignition

A. All engines using an approved non-HEI MSD ignition system must be equipped with an approved, unaltered, operational MSD #6430 6ALN, #6425 6AL or #64253 6AL ignition Control Box. The unit must be mounted under the access panel above the driver foot box.

B. All engines must be chipped or programmed to the following maximum engine RPMs. Chevrolet Performance 602 engines, 6,500 rpm and all optional, steel block/head engines, 7,500.

C. Series retains the right to change MSD boxes with any car at any time without notice.

IF YOU ARE CAUGHT CHEATING “WITHIN THE BOLTS” Driver is fined $1000 and suspended from  competition for 30 days. All weekly championship points are forfeited. Violating driver cannot compete at any sanctioned track in the Limited Modified during the suspension. Money is directly deposited into driver point fund. 2nd Offense – Will result in an immediate disqualification and a suspension will be set at one year(365 calendar days).

Fuel and Carb

A. One (1) four (4) barrel 650 cfm unaltered Holley Carburetor, art number 4777 r 80777 or Holey HP Carb part number 80541-1, (-2) will be permitted. Built motors must run (2) barrel unaltered cfm Holley carb part 4412. One (1) two (2) barrel unaltered cfm Holley carb part 4412 will be permitted. All carb components must remain unaltered. Any changes will result in disqualification for the event. Any alterations to the carb will not be permitted. Removal of choke assembly and air horn only. Must pass gauge inspections.

B. Air cleaner max height from air horn base 5”

C. 2” carb spacer, 1 spacer only

D. Racing gas or pump gas only. No alcohol, nitrous oxide, propylene oxide, nitro methane, or additives.

E. Fuel cell required. Must be contained in an approved container. Fuel cell not to be mounted lower than center of rear axle, with minimum two straps 1/8” x 2”

F. No belt drive fuel pumps

Clutch and Transmission

A. Transmission must have 2 forward gears and a working reverse. Must have functional clutch. No in and out boxes, No direct drives

B. Bert type transmissions allowed

C. Starter must be in stock location

D. Clutch-type transmissions must be equipped with explosion-proof steel bell housing. In lieu of an explosion-proof bell housing or if one is not available for your engine, a shield of at least 1/4″-inch x 6″- inches covering the clutch area 360 degrees securely fastened in place and fabricated from magnetic steel will be permitted.

E. All cars are required to have a drive shaft loop 12” from end of  transmission

F. All drive shafts are to be painted white. No aluminum or carbon fiber drive shafts.

Tires and Wheels 

A. Maximum 8” wide wheels. Bead locks are optional on right side only. Outside covers optional on all four tires.

B. Must be EMOD 26.5 or 27.5 A, AS, H, M30, M60 or American Racer

C. 9/16” or 5/8” wheel studs must be used on right side

D. Grooving and Siping of tires allowed.

E. Tires must pass durometer within manufacturer specs. Tires may be checked at any time.


A. Crate engines minimum weight 2,450lbs for crate and 2,500lbs for open motors.

B. Lead must be painted white and mounted with a minimum of two 1/2” bolts. Lead may not be inside the driver compartment or outside the body


(See drawing diagram below for reference – There may be dimensions referenced in the drawing diagram that are not referenced in written rules and vice versa. All dimensions whether written and/or referenced in the drawing diagram dimensions are rules(s).

A. All bodies must follow dimension(s) and the appearance as shown in diagram. The body shall be the fabricated modified body from approved vendors. The body must be symmetrical, including but not limited to doors, nose, sail panels, spoiler supports, etc.

B. The front windshield and rear window support must be stock appearing. The front window support(s) may have a clear Lexan support of no more than 16″ inches including the roof post at the bottom and going straight to the roof. The support must be securely fastened in a positive manner.

C. The front roof post must be in a straight line from top to bottom.

D. The sides of the engine compartment must remain open. Any side panels in the engine compartment area will not be permitted. A five (5″) inch maximum drop of the hood on either side of the hood will be permitted and it must be enclosed at the rear of the hood. The firewall on driver’s side must meet the front of the door.

E. The top of the doors must remain in line with the rear engine plate. The bottom of the doors may extend a maximum of eight (8″) inches past the motor plate toward the front of the vehicle. Any material that exceeds 8″ inches forward of the engine plate will not be permitted.

F. Right panel from top of door to bottom of door may not be no more than 3 inches and must be mounted straight inside the bottom.

G. A maximum one (1.0″) inch flange on the outside edges (left and right side vertically) for the purpose of strengthening only will be permitted on the front nose and roof only. Side fins and/or flanges of any kind along the length of the entire car (hood and/or front) will not be permitted.

H. A maximum of one (1) stone deflector, mounted only on the right side of the car, for rear mounted oil pumps, oil filters, and for the main oil tank will be permitted. The deflector may be made of steel, aluminum, or heavy gauge wire. The cover may only be mounted near the unit it and is designed to protect with a maximum size of eighteen (18″x18″) inches square and mounted only from the upper right frame rail to the lower right frame rail.

I. The minimum roof height is 42″ inches with a maximum height of 52″ inches.

J. The minimum deck height is 28″ inches with a maximum height of 39″ inches.

K. All cars must have a car number on both sides and the roof that are at least 18″ inches in height and 14″ inches in width.

L. The driver’s last name must be displayed under the car number in a legible font that is a minimum of eight (8″) inch high letters.

M. A minimum of two (2″) inches of tire clearance from the body is required.

N. The minimum ground clearance will be four (4″) inches.

O. The measurement from center of the hub to the rear top of deck will be a minimum of 34″ inches and a maximum of 48″ inches.

P. The maximum body width at the body’s widest part will be 72″ inches. The minimum of width at the body’s narrowest part will be 53″ inches. The top of the doors may have a maximum width of 67″ inches. The bottom of the doors may have a maximum width of 68″ inches. Q. On the left side, the rear of the door may flare out six (6″) inches for tire clearance.

Q. The bottom of the flare must be curved and rounded not pointed in any fashion.

R. The maximum rear width of car must be 67″ inches at the widest point.

S. The maximum roof width will be 50″ inches with a minimum of 44″ inches.

T. The maximum roof length will be 56″ inches with a minimum roof length of 41″ inches.

U. The maximum height on rear roof post vertical is 3″ inches.

V. The nose piece must not exceed 45″-inches in width, centered between the frame rails and must not extend past the leading edge of the front bumper. The nose piece must have a minimum of six (6″) inches from the ground to the bottom edge of the nose piece.

W. The MD3 03 Modified Aero Valance is approved.

Spoilers, Spoiler Braces & Supports

A. Only aluminum and/or Lexan and/or Lexan-type rear spoilers will be permitted.

B. The maximum overall height of the rear spoiler will be 5”-inches. The maximum width of the rear spoiler, including braces and/or supports is 67”-inches.

C. The rear spoiler must begin at the deck and extend 5”-inches from that point. Suspending the spoiler to create a wing-type device will not be permitted.

D. The rear spoiler must begin at the rear most point of the quarter panels.

E. Only three spoiler braces/supports will be permitted. The front edge of the spoiler brace/support must be in line with the spoiler.

F. The outside spoiler supports must not be mounted any wider than the top of the quarter panel(s) and must be centered on the rear deck.

G. In the event that aluminum angle is used to brace the upper edge of the spoiler, the angle must not add to the height and/or length of the spoiler in any way.

Interior and Driver Compartment

A. All windows must have a minimum 11″-inch vertical opening. The entire interior must have a minimum of 11 inches of clearance from the interior deck to the roof and all sections of the roll cage. The minimum window opening will be 12″ inches. The interior deck sheet metal to the right side of the driver from the back of the seat forward should be fabricated on an angle from the driveshaft tunnel to the right-side window to promote ease of exit for the driver through the right side and or front window opening.

B. A master ignition switch within easy reach of the driver is mandatory. The switch must be clearly labeled “ON” and “OFF”.

C. Hydraulic and/or pneumatic weight jacks, trackers, or similar adjustable components of any type will not be permitted.

D. Mirrors of any type will not be permitted.

E. The drivers compartment must be sealed from the engine and the race track. The rear bubble of the hood should be closed and sealed from the driver.

F. The maximum slope/rake of the interior sheet metal “shelf front-to-rear is 4”-inches when measured from the firewall to the top of the most rearward part of the rear deck. A maximum of 2″-inches of slope/rake will be permitted in front of the rear of the seat to the firewall and a maximum of 2″-inches of slope/rake will be permitted from the rear of the seat to the top of the most rearward part of the rear deck.

G. The top of the interior must be flush with the top of door and quarter panels. A one inch drop on the inside will be permitted when measured laterally from the top of the doors to the lowest part of the deck.

H. Any car in competition must have right side door bars as part of the roll cage. Please reference 15.11.B in the roll cage section of the 2018 UMP Modified Rule Book.

Roof and Roof Supports (see drawing diagram for reference)

A. All roofs must be full size. Half-moon roofs will not be permitted. The rear edge of the roof may not be mounted more than 12″ (twelve inches) past the rear axle. The roof must be symmetrical.

B. Wings, roof spoilers or ground effects of any kind will not be permitted.

C. All flat type roofs will be allowed a maximum 3″-inch difference in height between the front of the roof and the rear of the roof. This measurement may be taken from the interior and/or the ground. The rear of the roof must maintain the same height from side to- side.

D. All curved type roofs will be allowed a maximum of 5″-inches in the front and 2″-inches in the rear. The break in the roof must be within 6″-inches from the center of the roof.

E. Wedge roofs will not be permitted.

F. Dished roofs will not be permitted. Roofs must be rounded side-to-side. Bead rolls will be permitted.

G. The rear roof post must begin where it meets the back edge of the roof. The rear roof supports may not extend past the front side of rear upright of the roll cage.

H. The side vents on the front roof posts may extend rear ward from the lowest point, a maximum of 16″-inches, then at a 90-degree angle to roof for one (1) configuration, side vents must meet the outside of the car.

I. The roof side (sail) panel window size must be 10″-inches x 15″-inches and must match drawing number- 2- side view. There will be a tolerance of 2″-inches at the top and 3″-inches at the bottom. A maximum crown of two (2) inches will be permitted, measured from the center of a common tangent point on either side of the crown. The roof side (sail) panels must be symmetrical.

J. If the long roof side (sail) panel is being used a 1″-inch radius will be permitted.

K. Any sun shield must be on hinge for easy exiting, taping will not be permitted. The window opening must remain at a minimum of 12″-inches.

L. All race cars in competition must meet the measurements illustrated in the drawing.

M. There are only 4 (four) approved roof supports to choose from.

N. The roof should be single thickness of material. The roll bar hoops must be exposed for inspection.

O. If the roof is curved then a level will be placed on the top of the car and if the roof is 5″- inches or less in the front and 2″-inches or less in the rear and the break is in the middle then the roof will be permitted.

P. The roofs must be stock appearing. The roof must maintain the same height on both sides. If local track official determines the roof does not meet the requirements as stated above then a penalty as determined by the official may be determined prior to competition, additional weight and/or other penalties, unless the roof can be returned to within the parameter as stated above prior to competition in the event that the roof was inspected for.


A. One OEM style battery allowed. 14”x8” maximum. No 16v batteries. Must be mounted with a 3/8” rod and be mounted behind fire shield and out of driver’s compartment.

B. A switch to disable all power to car must be installed behind driver within reach of safety man at shoulder height and must be clearly marked on/off

Electronic Devices & Traction Control

A. All electronic and/or computerized wheel spin and/or acceleration retardation traction control devices will not be permitted. Controlled timing devices attached to or controlling accelerator or rotation of wheel will not be permitted.

B. All traction control devices utilizing wheel sensors and/or any means of measuring ground speed to control wheel spin will not be permitted.

C. Adjustable ping control devices, dial a chip controls, timing controls or automated throttle controls will not be permitted in cockpit or driver accessible areas.

D. Adjustable restrictor plates will not be permitted.

E. Any remotely controlled components inside or outside the cockpit of any competitor’s racecar will not be permitted.

F. Radios or devices for transmitting voice or data will not be permitted, either in the racecar or on anyone connected with the car.

G. The use of colored flashlights is prohibited

Claiming and Technical Inspection

Track reserves the right to check anything on any car at any time. All cars MUST meet requirements at all times. All cars MUST have a starter and battery capable of turning the motor sufficient to P & G. or, you MUST pull the heads for a cubic inch check. If any car is found to be illegal and is assessed a fine, the fine MUST be paid before the car, driver or owner will be allowed to participate in any events, regardless of the current owner of the car. The person registering as the owner will be considered such until notified, in writing, to the Association.

PROTESTING:  Cars running in a restricted class should be fully prepared for inspection at any time. Bring the necessary parts and personnel to re-install.

All cars MUST pass a technical inspection. You MUST be a participating driver or registered owner of a car participating in the race program THAT night to submit a protest and to have finished in the top 5 in the feature event.  Any protest for legality MUST be made within 15 minutes after their respective feature is completed. ALL protests MUST be specific and in writing as to what is to be checked. Cars protested will be torn down at a cost designated by the protest man.

Open Motor: Cost to check bore & stroke and CC head is $150.00. To remove the oil pan and check anything in the motor is $250.00. A minimum of $10.00 cost for a protest is required for a visual inspection. This cash money will be turned over to, and held by, the protest man until a determination as to legality is made. If the car is found to be illegal, the money will be refunded to the protester. If the car is found to be legal, the protested car owner will receive the money. During the tear-down, ONLY the protest man and two (2) men from the protested car, the protester and designated Officials will be permitted in the impound area. Illegal parts may be confiscated by the Association.

Crate Motor:  Cost to check stroke is $50.00. To have the engine sent off to a certified inspector for inspection of tampering inside the engine is $500.00.  Minimum of $10.00 cost for a protest is required for a visual inspection. This cash money will be turned over to, and held by, the protest man until a determination as to legality is made. If the car is found to be illegal, the money will be refunded to the protester. If the car is found to be legal, the protested car owner will receive the money. During the tear-down, ONLY the protest man and two (2) men from the protested car, the protester and designated Officials will be permitted in the impound area. Illegal parts may be confiscated by the Association.

Anyone refusing to tear down will be considered illegal.


Illegal cars will forfeit monies won, loss of points for that night and will be assessed a fine as follows:

First violation: $100.00 fine
Second violation: $500.00 fine
Third violation: $1000.00 and suspension from track for the balance of the season.

All fines will be carried over to the next season if not paid. You cannot race until fine is paid.


A. All cars must have a sturdy seat belt and safety harness, three inch seat belts required. Must be 5 years or newer and date on tag must be visible

B. Five point safety belts and flame resistant racing suits required

C. Gloves recommended

D. All drivers must have an approved racing helmet

E. Window net recommended

F. Head and neck restraint systems highly recommended

G. If you do not have a full containment seat you must run a window net

WISSOTA RULES (for their cars)

IMCA RULES (for their cars)

USRA RULES (for their cars)

No weight needed in front for transmissions

Can run Hoosier tires. NO D tires

If it doesn’t say you can do it, it is not legal! Rules may be amended or changed as necessary throughout the season. It is the responsibility of all participants to know the rules.

Situations not covered in any of these rules will be handled at the discretion of the track officials as they arise.

Decisions of track officials are FINAL!!!