How to Build a Race Car Frame

Race car frames must endure great punishment. Therefor the frame must be built strong to withstand the punishment of high speeds and even survive a crash. What doesn't need to be strong are the bolt on suspension parts. In the event of a crash the energy must be absorbed somewhere in that race car, let it be the bolt suspension. The suspension parts can easily be replaced. Protect the frame because it is more difficult to repair or replace. For example purpose, this article is based on a 1980 Chevy, Chevelle frame.

Things You'll Need

  • Safety glasses
  • Jack stands
  • Hammer
  • Dust masks
  • Wrench set
  • Socket set
  • Wire brush
  • Acetylene torch
  • 4-inch grinder
  • Reciprocating saw
  • MIG welder
  • 2 3/16-inch by 5-inch round plates
  • 4 1-inch by 8-inch threaded rods
  • C-clamps
  • Sand blaster
  • Compressed air
  • Blasting sand
  • 1/8-inch by 4-inch plate steel
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Instructions

    • 1

      Place a stripped down car frame on four jack stands. Select the car frame that best suits the rules for the race car class intended for competition.

    • 2

      Clean the entire frame by blasting it with a sand blaster, if available. If a sand blaster is not available use a wire brush on a drill or grinder to completely clean the frame of dirt and rust. Use a blow gun and compressed air to blow the frame and frame seam free of debris. Use an acetylene torch to heat the front frame seams on top and bottom to crack any hidden sand trapped in the seams and to prevent weld contamination.

    • 3

      Reweld the factory seam welds on the top and the bottom of the frame. Use a hammer to peen the frame seam closed for welding. The factory weld is not suitable for race competition. Re-weld the factory welds on the left and right upper and lower A-arm brackets.

    • 4

      Weld a 3/16-inch by 5-inch round plate directly centered over the stock front spring pockets in the frame. Drill a one inch hole in the very center of the 5-inch round plate and weld a one inch nut to accept the threaded rod for the jacking bolt.

    • 5

      Clamp the 1/8-inch steel plate to the inside C-section of the frame to form a box that reinforces the frame. The C-section of the frame is the area of the frame rails that is three sided usually from the cowl area on back to the rear bumper. Manufactures use the frames' C-section to run brake lines and gas lines from the front to the rear. Tack the steel plate to the entire C-section of the frame, then weld the entire plate to the original frame on top and bottom. Weld in small beads to avoid excess heat build up in the frame metal.

    • 6

      Reweld the factory rear trailing arm mounts to the frame. Cut the top frame shelf from the rear kick up, if rules permit. The top frame shelf is the stamped plate that seats the top of the rear coil springs and shock mounts.

    • 7

      Insert and weld a length of 2-inch by 4-inch by 1/8-inch thick flush with the top frame kick-up. Lay the tube horizontally directly over the intended rear spring position. Use the rectangular tubing for the jacking bolt mounts and shock mounts. If the race car is to use conventional springs, hole saw the rectangle tubing and install the large 1-inch nuts that will house the spring jacking bolts. If the car will use coil over shocks, drill the tube for shock mount slugs to be welded into the tube.

    • 8

      Redrill the upper A-arm mounts so that theyare level when the frame is level. This is done by drilling a new front holes below the original hole in the frame mount. This will reduce the or eliminate anti-dive percentage from the race car geometry. Anti-dive interferes with the shock and dynamically changes the spring rate because anti-dive causes ball joint bind.