Muscatine County Fair Book - Demo Derby Rules

Demo Derby Rules

Check-In Time

Tech is 8am to 10:30am Driver’s Meeting is at 10:45am

Show Time

11:00 am



  • Kid’s Power Wheel Derby
  • 80’s Full Size/Bone Stock Cars
  • Stock Compacts
  • Powder Puff Classes!

80’s and Newer Bone Stock Cars

Build Rules

  1. No limo’s or convertibles.
  2. All cars must be stock unless modification is specifically stated in these rules.
  3. All glass, plastic, chrome, and interior must be removed from car before arriving to the derby.
  4. All trailer hitches and braces must be removed.
  5. Batteries must be moved to the passenger floorboard and properly secured/covered.
  6. All cars must have working brakes when you come for inspected. If the car is not able to exhibit the ability to stop it will not be inspected.
  7. NO welding other than what is mentioned in this set of rules. If your car is found with any weld, other than what is allowed, and you refuse to fix it to the judge’s satisfaction, you and your car will not run.


  1. Remove all glass mirrors and plastic. Remove all decking in wagons Vehicles must be swept clean of all debris
  2. No crease enhancement, no sheet metal or frame shaping, forming or folding.  Deck and Hood must be 100% in stock location and open for inspection. After inspection you may tuck trunk with a single 90-degree bend.
  3. Fasten trunks, hoods, tail gates in 4 places, 2 strands of #9 wire or 3/8 bolts with factory washers to sheet metal only or 4 spots of 2x2x1/8 welded on the trunk. 4 spots of 2×2 angle 2 inches long with 3/8 bolts may be used on the hood or trunk instead of as well. You may weld doors 12 inches total on each vertical seam only2”x1/8” Strap. Drivers door may be welded solid. Drivers door may have an 1/8” door skin that may extend 3″ past the seam.
  4. Body mounts and spacers to remain stock and in place. If they are broken or rusted out, a single piece of #9 wire may be substituted or a 7/16 bolt with a factory washer. No body bolt changing allowed. Exception: You may replace two front body mounts with two 5/8” threaded rod with eight 3 inch washers and 4 nuts, bottom nut and washer must be inside the frame and may extend through hood. ZERO welding allowed to mount this rod. Core support spacer may be 2×2 up to 3 inches tall. You may also replace the 2 behind the hump with 5/8” all thread with same washers allowed as core support one.
  5. #9 wire or chain required in front windshield. You may also use 2” inch or smaller material welded 3”on the roof and 3” on the firewall, up to 2 spots.
  6. Rust repair. The only rust repair allowed will be in the floor/ trunk pans only! Must be 18 gauge or thinner material. Skip welded 1”on 1”off. 1”past rust. Again only the pans!!! Nothing else!!


  1. Tires no bigger than 16 inches
  2. No split rims
  3. No studded tires
  4. Doubled tires are ok
  5. Any rim
  6. No beadlocks
  7. No solids.


  1. NO welding on frames allowed.
  2. No suspension modifications allowed. Must remain strictly stock. No aftermarket parts.
  3. You may use 2 twist in spring spacers per side (store bought, no homemade) 3. You may use a single strand #9 wire to hold coil spring to rear end and leaf sprung cars may use 4 single strands #9 wire as leaf clamps. May weld 1 2x2x1/4 strap on each upper a arm

Drive Train

  1. ANY drivetrain allowed with the following criteria.
  2. Only the lower stock engine mounts may be welded to cradle only. You may use two 1/2″ thick spacers to raise engine to clear steering components, may not exceed rubber mount area. You may extend off back of cradle but nothing excessive, 1/2″ flat plate only
    (example SBC in Caddy, Mopar)
  3. No tranny protectors no aftermarket cases or tails, stock mounting only, stock crossmembers only, or a straight piece of 2x2x1/4 in factory location. May use 2x2x1/4 angle iron 4”long for mounting. An ultra bell is the only modification allowed to the transmission.
  4. Rear End Swaps Allowed: NO bracing. You may use a factory 9 inch or 8 ¾ with factory lower brackets off of a coil spring rear end or the leaf/coil conversion pads and weld on uppers with a rubber mount. Call Austin on how to mount it. Must be factory axels. Max axle size 31 spline. NO fabricating or welding allowed of axles or rear end (inside or outside). You may weld rear end gears only.
  5. You may run 1 piece of 3/8” standard chain from rear end around the frame OR 2 strands of #9 from rear end to frame, nothing thru body (# 9 wire can have 2 loops, 4 strands together in center twist only.) One or the other, can’t do both. May also run a piece of 3/8 chain from rail to rail in the rear may not be welded.
  6. Aftermarket Cable Shifters, Gas Pedals, Steering Columns & Headers are allowed. Clarification: None may strengthen car.
  7. Lower engine cradles only. No skid plates, protectors of any kind, no aftermarket parts of this nature at all.
  8. You may swap engines, example: Chevy in a Ford.
  9. Slider drive shafts are allowed.

Driver Compartment

  1. 4-point square cage only with one 2×3 down tube to frame in the center of the door for protection only per side. max 60-inch side bars 6 inch max cage material. Halo bar is mandatory to back seat bar or floor sheet metal. Gas tank must be mounted horizontally and 8 inches off floor. Gas Tank Protector. 24 inches wide and may be the height of the tank may go against package tray.
  2. Drivers door must be padded.
  3. Gas tank and battery must be moved and secured. Tank behind the seat, Battery centered in the passenger front floor.
  4. Nothing may be mounted in a way that strengthens the car.
  5. Tans coolers allowed. Must be mounted inside 4-point cage area.

Tank Protector

  1. 24 inches wide and may be the height of the tank.
  2. Drivers door must be padded. If you have a passenger please pad theirs as well.
  3. Gas tank and battery must be moved and secured. Tank behind the seat, Battery centered in the passenger front floor.
  4. Nothing may be mounted in a way that strengthens the car.
  5. Trans coolers allowed. Must be mounted inside 4-point cage area.


  1. Replica bumpers allowed or You may weld on any loaded (loaded on inside only, nothing on the outside) factory OEM bumper, or a simple piece of 4×6 or smaller tubing. You may weld the stock bumper bracket for the car or the bumper to frame 4 inches from the back of bumper, single pass only.
    • In addition, you may put 4 one-inch welds on back side of bracket or to weld shock inside frame (example Crown Vics). All bumper material longer than 4” back must be removed.
    •  Bumper may have maximum 15’’ point
    • Point must span 36’’
    • 8’’ tall max
  2. Shocks may be collapsed and welded. All shocks and brackets in stock location only and extended one inch in front of frame.
    •  ALL bumper brackets and shocks must be in stock location. Or
    • You may shorten to one inch in front of the core support space and hard nose with no shocks or brackets on car. Or
    • You may chain, one piece of chain per side BOLTED from the mount to mount to hold on the bumper.
      Only welding allowed is doors, bumper, engine mount, cage and rear end gears!

03 & Newer Rules

  2. Must use factory rack & pinion, no steering box conversions.
  3. Must run the factory aluminum cradle with no modifications. You may run a gray arear style cradle. The only spot it may attach are the aluminum towers. It may not touch the frame rail, or where the aluminum cradle bolts to the frame rails in any way. The aluminum towers are the only attachment point. If inspector deems the cradle is being used to strengthen the car, the aluminum cradle, or brace the steering components in any way, you will remove it or you will not run. Use this as a motor mount, nothing else.
  4. Must follow all other rules, any questions call before assuming it will be OK!!!!!
  5. Plate Rules:
    1. Fresh Cars: (2) 6x6x1/8”
    2. Plates must be 1-inch apart including the weld
    3.  1⁄2” weld max.
    4. They cannot touch or be attached to the driveline components at all.
    5. No fix it plates allowed on pre rans
    6. 9 wire on pre rans will be allowed 2 spots per window opening, and 6 spots elsewhere
    7. Must be used in a twisted method to hold something. No using it to stuff between 2 objects

2024 Stock Compacts Rules & Powder Puff Class Rules

  1. Powderpuff class must be fresh cars
  2. Car must be completely stripped , all glass out. Dash may stay in the car. Fuel tanks must be removed and relocated to inside the back seat area and covered. Fuel tank can be mounted to back of cage bar or bolted to the floor. Must have a 2” gap between fuel tank protector and speaker deck area.
  3. Batteries must be secured and covered good.
  4. Roof sign with name or number or both.
  5. No body shaping , crease enhancements or wedging.
  6. Engines must be factory to the car. No sub swaps. No convertibles. Carb conversions is ok but no protectors.
  7. Minimum of back seat bar and driver door bar. 3×3 material no bigger. 2 down bars allowed 1 down bar per side can be ran from cage to floor and bolted to floor between the front door seams.
  8. 2 front windshield bars must be added. 9 wire, 2×2 straps, chain
  9. Drivers door may be welded shut. Every other seam can have 3 spots of #9 wire , 5/16”chain loop, 2”x2” plates.
  10. Hood and Trunk must have 12”x12” hole in them.
  11. 2 allthread may run through your front body mount up through hood to secure hood. No bigger than ¾”allthread. 2 extra 6” long bolts may be welded to strut tower to secure hood max ¾” allthread.


  1. Stock appearing compact bumper stuffed OR a 3”x3”x¼ inch tube may be used for a bumper.
  2. You may use a 6” piece of 3”x3”x1/4” tube put into frame with a hole behind it for inspection or ¼” flat steel starting at bumper to mount bumper so bumper does not fall off.


  1. May run any tire on the front.
  2. Rears must be donuts or forklifts.
  3. Wheel protectors are not allowed.


  1. Must remain stock

Presets Color