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240 TURBO SCOOP MODIFICATION TO AIRBOX
by Paul Schuh

This is a bit more radical alternative to modifying the 240 Turbo airbox. It costs a little more and takes more time than the PVC pipe mod, but it really opens out the front of the box.. This mod continues to utilize the factory air filter in its current location but essentially places your filter well into the air “pressure front” at the nose of your car.

This modification requires you to work with fiberglass. Do not be afraid! It is not difficult, in fact the first time I ever saw fiberglass materials was when I decided to begin this project. Take your time and you should not be disappointed.

CAUTION: both the fiberglass materials and gasoline required to complete this project can be hazardous if mis-handled. Complete this project in a well ventilated area, not your basement. Dispose of hazardous waste properly.

Most of the material required for this mod are available at a well stocked hobby supply store:

  • Approx. 1 ft by 1 ft block of styrofoam. (You may want to get extra so you can experiment with shapes.) This will be used to model the shape of the scoop
  • Fiberglass cloth This will form the body of the scoop
  • Fiberglass resin (usually comes in quart metal container. A quart should be enough) This will interact with the cloth to harden the body
  • Flat black spray paint To color match the scoop to the airbox
  • Half a gallon of a gasoline Used to dissolve styrofoam from finished scoop
  • Sandpaper (various grits) To rough up and smooth out various parts of the project
  • Sharp knife and coping saw To cut airbox and radiator support
  • Cheap paint brushes To spread fiberglass resin

Preparation: If you can find one, get an airbox from a junk yard so you can take your time with this and not install it until you’ve got it just the way you want it. Otherwise, start by removing the airbox from the car as described in the “PVC Pipe” procedure. Remove the diverter flap and all of the side piping. Thoroughly clean the box of any grease, oil or dirt.

  1. Cut out the front, and side of the box to include the side tube that leads down to the diverter valve. There is no need to cut beyond the mid-point of the sides (proceeding from front to back). Extend your cut into the bottom of the box up to a point about three quarters of an inch to where the air filter seals to the bottom. CAUTION: DO NOT get too close to the filter because if it does not seal well, you will suck in unfiltered air. Also, DO NOT get closer than three quarters of an inch to the rim at the top of the box. You need to leave some material to attach the scoop to and you need the rim to maintain its rigidity to still seal well with the airbox top. By this point you will have removed about 30% of the material that comprises the box. Set the box aside.
  2. In order to proceed, you will first need to provide a larger opening in the radiator support for the air to pass through. I started with the small circular opening that the existing tube passes through and extended that hole towards the right side of the car to incorporate another existing hole:

 

 

Feel free to experiment with other shapes and sizes. Just make sure to eyeball the back side of the radiator support to make sure your scoop will be able to cover the whole opening. The opening could actually be quite larger than I made it. I just didn’t want to take too much material out of the radiator support. When you’re happy with your opening, smooth out the edges with sand paper.

  1. If you cut-out a junk yard airbox in step 2, at this point you will have to remove your existing airbox. Place the cut-out airbox on its mounting point and picture in your mind the approximate size and shape of the scoop that will be needed to fill in the opening in the box to the opening in the radiator support. In my case, the hole in the support was well below the airbox so my scoop had to sweep down. The hole in the support was also smaller than the opening in the box so the scoop had to change in area of cross-section.
  2. Place the styrofoam block in the cut-out of the airbox and secure it with masking tape around the sides and bottom.. Begin shaping the foam by removing material with a knife, saw, or sandpaper. Check your progress frequently by placing the “work-in-progress” in the car to see how things are “shaping up.” This will be the most tedious part of the process. Patience.
  3. When the scoop is shaped the way you want it, use a marker to draw a line on the foam just outside the box at the point where the foam enters the box, then remove the tape and foam from the airbox. Now you will “build-up” the fiberglass scoop over the foam up to the point of the line you just drew. Follow the directions on the resin can for laying the ‘glass. It will be a several step procedure with resin impregnated cloth wrapped around the foam, allowed to dry and additional layers added for strength. It’s best to work with the cloth in strips about 3 inches wide. The exact dimensions on the edges is not critical because the ‘glass can be shaped and smoothed inside and out when dry. Just make sure you get it thick enough to have some extra material to sand if you’re worried about smoothness.
  4. When the scoop is fully dry, test fit to airbox to make sure you got it right, including checking it in the car again. When you are satisfied, pour gasoline on the foam . This will melt foam but not harm the fiberglass. Thoroughly clean out scoop of foam and gas. Attach scoop to airbox using additional strips of fiberglass around sides, bottom and a little at the top under the lip (you did leave room, didn’t you?) Rough up the airbox where fiberglass will mate using rough grit sandpaper. This will help your resin wet cloth “glue” to the plastic.
  5. Let your new airbox completely dry. Test fit in car again and sand front edge of scoop if necessary to get a close fit to back of radiator support. Sand any other rough spots inside and outside of scoop. Clean out scoop again. Your new scoop will be a opaque white color. Spray flat or semi-gloss black to match airbox.
  6. Re-install new airbox, filter and fuel distributor into car.

Congratulations.

 

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