Installing a fiberglass cowl or hood scoop to your vehicle's stock steel hood will give your car a very aggressive look, while also improving the cooling of the engine by providing more cool air to your engine's intake. With a friend's help, using fiberglass lets you firmly secure a cowl to steel without the worry of cracking, bulging or increasing the weight of the hood.
Place the cowl or scoop on your hood and determined where you would like it mounted. Trace the outline of the cowl onto the hood using a marker.
Sand the hood around the marked perimeter line you drew in Step 1. Remove all clear coat, gel coat and paint down to the metal to ensure a good bonding surface between the cowl and the hood 3 inches on either side of the outline.
Place the cowl onto the hood; have a friend hold it in place. Drill holes through the cowl and the hood using a 3/32-inch drill bit every 2 inches around the perimeter of the cowl.
Cut a hole if you want to allow the passage of air through the cowl. Mark the outline of the hole, then cut it using the edge of your angle grinder.
Mix the epoxy resin and hardener together following the manufacturer's instructions. Apply the mix with a paintbrush to the mating surfaces of the cowl before placing the cowl onto the hood, aligning the drilled holes made earlier. Rivet the cowl in place by placing 3/32-inch rivets through the holes and tightening in place using the rivet gun. Repeat for all drilled holes around the cowl.
Place sheets of fiberglass cloth around the seam where the cowl and the hood meet, then paint on epoxy to saturate the cloth and mold the cowl into the hood. Try to get out all air bubbles and smooth the surfaces of the fiberglass as much as possible, as it is much easier to blend fiberglass when it is still wet than when it has dried. Allow 24 hours for the fiberglass to cure and harden before continuing.
Sand the hardened fiberglass smooth to the hood using 200 grit sandpaper wrapped around a sanding block. Mix polyester or fiberglass body filler and apply it to any uneven seams between the cowl and hood using a putty knife. Smooth with a rubber spatula. Allow the body filler to cure according to the manufacturer's directions.
Sand the body filler smooth to the surfaces of the cowl and hood using 400 grit sandpaper, followed by 800 grit wet-dry paper to prep the hood for painting. Finish with primer, paint and clear coat.
