SLC Manual: Rear Window Vents
The optional rear window vents are a great solution to engine compartment heat buildup. While the Le Mans has a large vent area over the engine, the SL-C (including both the race and street tail versions) needs better venting. Available in both pre-finished, ready-to-install carbon fiber, or fiberglass (which needs normal paint prep), they are easy to install. Here's a picture of the carbon fiber vents installed on a car with a race tail:
Tools and materials needed:
Jig saw with fiberglass cutting blade, sandpaper (80, 120, 180, 400), long sanding block, 3/4" or wider painters tape, double-sided tape.
If you are installing a fiberglass set, you'll also need a Dremel tool, a small file set with flat edges, and a fiberglass cutting dremel insert, 600 grit sandpaper, and your choice of primer and paint.
Optional:(8) 10-32 flathead screws and 10-32 nylocs, allen wrench for the screws, and regular wrench for the nylocs. Drill, 3/16" drill bit, countersink bit if using the flatheads. Border paint for edges if desired. 3M 8115 panel adhesive in lieu of the screws if desired.
About 8 hours, from beginning to end for the fiberglass versions, about 6 hours for the carbon fiber versions.
If you are installing the carbon fiber version, skip to the next step. For the fiberglass versions, you'll need to begin by opening up the slots if they haven't already been done for you. Use a dremel to get close to the edges, then clean them up with a small flat file. Once you have the openings cut out and trimmed to your satisfaction, spray the vents with primer, sand to the 400 stage, then re-prime and sand to the 600 stage until ready to paint. Spray with your selected color and allow to dry according to the manufacturers instructions on the primer and paint.
Opening up the window area:
Once the vents are ready to install, you'll need to remove the existing rear window, if present. Trim the sides of the rear body section window opening to have a flange of about 1/16" less than the width of the outside edge of the vents. Leave the existing top and bottom edges at their typical 1.5" to 3" flanges to begin. Once the initial window opening flange on each side is trimmed, place the vents in place in the window opening and mark where the top and bottom still need to be trimmed. Use a Dremel or saw to carefully trim the flanges around the edge of the window opening until the new vents just drop in.
Note the top and bottom window opening flanges; you'll need to trim your opening in a similar way. Be sure you use the vents you have to mark the exact shape you need. If you cut too much, you can fiberglass some scraps back in and repaint if necessary.
Trimming the window:
With the new vents laying in the window opening and taped in place with painter's tape, carefully place the existing polycarbonate window over the opening and the vents, Using a sharpie, mark where the window needs to be trimmed to fit into the flange on the vents. Be sure to mark the window a 1/4" or more wider, so you can carefully work the window to the correct shape with sandpaper later, and so the Sharpie marks won't show in case you were a tiny bit off while marking.
Once marked, remove the window and cut and sand the edges as described here. Carefully work the window edges to shape, frequently checking the window for fit. Remember, you can't un-cut or un-sand the window! Tale your time, and work carefully.
Fitting the vents:
Once you have the window trimmed so it fits the new opening bounded by the vents on the sides, you can carefully sand the edges with smoother paper to get a smooth surface like the originals; work up to 400, and you'll be surprised by how good they look.
You can now mount the vents in the window opening. If you are using only double-sided tape, prepare the flanges on the body by cleaning them with a degreaser, and a final wash with alcohol. Similarly, prepare the underside of the vents as well. Lay down strips of double-sided tape on the body flange and check for correct clearance. If you need more, you can double up on the tape.
Remove the top layer of the tape to expose the adhesive and lay the vents back in place so that they are in the same place they were when you were trimming the window.
Allow the tape a few minutes to develop the adhesive bond.
Fitting the window:
Once the vents are fitted and the double-sided tape is dry, lay the window in the opening to check for final fitment.
If you choose to use border paint, apply it now and allow to dry for 24 hours before proceeding.
Once the window is in place, attach it to the vents by using the 10-32 flatheads. If you are using border paint, the window can alternatively be permanently attached to the vents using 3M 8115 panel adhesive,, or with more double-sided tape. If you use the flathead screws, be sure to carefully countersink the window so the screw heads are flush with the window surface.
Using screws to attach the window to the vent is the most heat-resistant, and allows easy removal of the window, at the possible expense of a really clean look. The tape is semi-permanent, and like the panel adhesive looks best as it can't be seen under border paint, but it really is pretty much forever, so think about what makes sense for your situation.