I have been bragging about my hoodscoop on here for a year now, and never thought to post a how to, just-in-case someone else wants to give it a try. The goal is not to teach people how to copy mine, but instead the basic steps necessary to do your own.
1. The first and most imprtant step is to come up with an idea of what you want it to look like. If you are working alone a drawing is not important, but unless you have a plan, you will not know when it is right or when to stop (haha). Try to make sure that your ideas are not too complex, overhangs become a problem in one of the next steps.
I decided I wanted something like a GTO, but modified to match my cars lines. I had a number of ideas and it took more time to plan it than build it. My insperation...
I had never worked with fiberglass before so I had no idea how to do it. I got luck and Musclecars on Spike did an episode on how to make fiberglass fender flares for a Mustang (mentioning that this was what I copied is how I got on Spike. the following steps are my version of their instructions.
2. You will need to make a form. I used that green foam used to mount fake flowers (per Musclecars). You can get it at craft stores in verious sizes and thicknesses. Next you need to layout the location for the scoop on your stock hood. I used masking tape to and a Sharpie to mark the hoos. Make sure to find the actual center and work very careful to stay symetrical to it. Screw this up and the scoop is off center or crooked. Drink a bottle of alcohol for courage.
3. You will need to cut the foam to your shape. First make it contour to match the hood. I recommend hollowing as much of the bottom out as possible (1" deep should do) so you only have to make the edges level instead of trying to match the contour. You can use multiple pieces of foam if necessary, just tape it together with duct tape to make sure it fits together and lines up, use dowles to align it (I used broken pencils - they shove right in).
To shape the foam sanding works the best since it is hard to cut the stuff to shape with a saw. I used a broken hacksaw blad to cut the rough shape and sanded from there to get closer (rubbing a piece of the scrap foam against your piece works suprisingly well).
I cannot stress this enough - Make sure your foam is exactly how you want it. Make sure all of the surfaces are straight and recut anything you need to. It is much easier to work in foam than bondo.
- sorry it is blurry.
3. Tape the blank to the hood and make sure it is straight and even Then cover it in tin foil. Smoke 2 to celebrate.
4. start pouring fiberglass resin on the scoop and spreading fiberglass mat over it. brush the resin over the mat as you work. you need to make sure it is saturated. Extend the fiberglass at leat 1/2 to 1" onto the hood. I used 2 layers of cloth and a good chunk of a can of resin.
5. Let it set-up for a couple of hours, then go out and pop it off of the blank. Work carefully not to damage the scoop, but if it breaks at this point it is not strong enough anyway. This is the point where the complexity of the design or overhangs become and issue. You have to be able to get the blank out.
6. Now you have to attach it to the hood. First remove and discard the blank (unless you plan to make another - they can be reused). Now place the scoop on the hood exactly where you want it. Drill small holes around the base (the fiberglass that extended over the hood) and through the hood . Remove the scoop and apply adhesive (I used GM panel adhesive - same stuff the glue quarter panels on with). I held it in place while it dried with klicos and then replaced with rivits once the adhesive dried. you could probably just rivit right off.
7. Once it sets up you can start blending it in. First grind the base a little once the glue has dried to thin it down and apply bondo around the edge to fade it in (I went 6" in each direction). Now correct the surface imperfections to taste. I am picky and did not do a good enough job on the blank so it took me a few weeks of work. I think if I did it again I could save allot of time by doing the blank better.
8. Prime and check for flaws
8.5 re-prime before final paint
9. Thow a party and celebrate. Try to get on TV
Oh yeah, to make it functional cut a 12" hole over the carb before you glue it down. Then get a 14" drop base filter and a 9" filter. Put the 9" filter on the center of the 14" base and tighten down. Get some 4" hoodscoop foam from Summit and make it into a 14" OD circle and glue it to the 14" drop base where the filter normally goes, and cut to fit contour of hood. The opening in the 14" OD foam is 12" so it lines up with the hole in the hood to seal the air filter to the hood isolating the incoming air and is flexible enough not to cause problems