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How to Build for the IMCA Modified

The International Motor Contest Association, or IMCA, is an organization that promotes auto racing events. Only a handful of particular types of cars are allowed to be raced under the IMCA -- one of which is the Modified. The Modified is a GM Chevelle race car that has an open wheel front and a closed back end, similar to a stock car. This car is found in the top division races of the IMCA. People who are interested in building for the IMCA Modified must familiarize themselves with the association's rules.

Things You'll Need

Measuring tape

Instructions

- 1
  Read the IMCA's published rules for Modified race cars. Each year, the IMCA publishes updated rules that may include changes to the frame dimensions or other specifications. If you want to build for the IMCA Modified, you must know what types of dimensions and frame structures apply to the Modified so that you are not disqualified before the event.
- 2
  Build the very back of the Modified -- behind where the driver sits -- to be 41.5 inches wide, from frame rail to frame rail. The frame rails are the last part of the Modified, similar to a tail.
- 3
  Make sure that the distance between the side rails at the lower steering gear bolt and the idler arm mounting surface does not exceed 28.5625 inches. This spot is located in front of the frame rails, moving closer to where the driver sits on the underside of the vehicle.
- 4
  Measure the distance between the weight bolt nuts. Place the measuring tape or yard stock at the top of the frame and check to make sure the distance is no greater than 34.25 inches and no less than 33.25 inches. This measurement is allowed to have a 1/2-inch tolerance, according to the IMCA.
- 5
  Keep the distance from the frame horn hole -- on the bottom of the car -- to the front edge of the second hole under 41.0625 inches. The frame horn holes are on either side of the car. Either side of the car also has lower ball joints. The distance between the center of the ball joint and the front edge of the side hole shall be 18.375 inches.
- 6
  Locate the cluster of four holes lined up in a row on the left and right sides of the underside of the Modified. Find the two parallel holes that are closest to the back or tail of the vehicle. Measure the distance from the center of one hole to the center of the opposite hole, to make sure it is approximately 52.375 inches.
- 7
  Move up to the top of the Modified now that you've completed the measurements for the underside. Measure the back end frame rail from top to bottom, to find out how tall it is. To be in compliance, the frame tail must be 16.75 inches tall. The lower indentation of the frame rail has to be measured also, and must not exceed 13.125 inches.
- 8
  Measure the distance between the indentation of the frame and the front section of the Modified, where the driver window ends. This distance must be 43 inches. The side rails in the front have to be 4.375 inches tall, from top to bottom. Make sure that you take into account the 6-inch ride height with tires.

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