I intend to run a cross ram intake with twin Holleys as per the Trans Am racing Camaros, so I decided to make an airbox on the underside of the hood from fibreglass to replicate the original steel ones. My hood is an original cowl induction hood, but the underside will foul the new airfilter arrangement for the crossram. I first started by placing the airfilter base to the underside of my hood to see where I need to trim steel to make it all fit once completed. The tape marks show where the factory airbox runs under the hoods inner skin.
I drew a line around the filter base to see where things were. The two circles drawn on the hood shows where my carbs will fit.
A friend of mine in the US, (Thanks Musclecar John
) sent me some dimensions from his friends crossram hood, plus I'd scaled it all up from photos to make sure it was correct in shape & size, to replicate the factory item. I then used some expanded foam & cut out the desired shape for the new airbox. I then sanded it all down to get it right.
Normally if I were to make a few of these then I'd make a mould to produce them, but because this was only going to be a one off I chose to make it direct from fibreglass instead. I put masking tape over the airbox & the surrounding parts of the hood, this will stop the fibreglass from sticking to the expanded foam once it's all pulled off.
The surrounding area was then masked out with paper to stop any fibreglass getting where it's not needed
The fibreglass resin & matt were then applied. I used two layers of 450 gramme matt, with the resin being rollered between coats to remove any air pockets or bubbles.
Once fully cured I was able to trim out the centre to the desired shape to fit the airfilter. Next up is to grind down the new panel & give it a light skim of filler to finish it off. Then I can remove the panel from the hood, remove all of the expanded foam from inside & trim the surrounding edges to the desired shape. I can then cut away the surplus metal from the inner hood skin & repair that to make it look as if it rolled out of the factory that way.