[fezz-man]

I had to cut open part of the upper indent on the firewall to give room to a distributer on my 51 GMC truck. I do not have the tools or skill yet to weld in a panel with complex curves. I want to fiberglass it in and was wondering 3 things:

1. Will the fiberglass be able to handle the heat of my high horse SBC? The fiberglass will only be directly behind the cap of my distributer.

2. I read about a few guys using chicken wire as a free-form type form. Can this be sandwiched between the layers of fiberglass or does it need to be removed?

3. In the process of building thickness, do you need to sand between cured coats, and will the glass stick well to sanded bare steel?

Thanks

Fezz Man

[302 Z28]

Do not use chicken wire, it will not hold up well. Check page seven of my photo gallery and see how I did just what you are asking. Of course my body is fiberglass, but the technique is the same. I used 1/8" masonite to build the form and shape I needed. I then laminated several layers of thick resin soaked fiberglass mat on both sides. The best way to do yours is with metal, but since you asked about the fiberglass, yes it will withstand the engine heat just fine.

Vince

[powerrodsmike]

One time I was hard up for a distributer cutout so I took a fire extinguisher, taped off the hollow in the bottom, built a glue flange on it with cardboard and a hot melt glue gun,, waxed it up and used it as a mold.
You really don't want to try to lay up directly on the steel firewall. It won't stick to the steel as good as it could if you made the part and glued it on with panel adhesive or epoxy.

If you want to do a quick and dirty one, rough up the steel, spread a thin coat of bondo. when that cures, sand the bondo until the paper doesn't clog, Then you can lay up over that. The bondo will act like a primer for the resin. You could cut the firewall , then position your form in the hole, then lay up over it.

You can build a form from anything that will hold it's shape, and won't react with the resin. I've used cardboard, pots and cups from the kitchen, carpet roll cores, oxygen cylinders, made them from wood (like vince )
urethane foam. Tape it off and wax it up.

If you use laminating resin, you don't have to sand between coats other than to sand any prickly hairs /lumps down that will mess up your layup. (sanding resin is the one you have to sand)

Hope this helps, mikey

[fezz-man]

well, thanks for the advice. I am going to attempt to fill in the gap tomorrow.


Is ther a maximum thickness of matting you want to build to? Can you do it all in 1 shot or do you have to let it cure and build in stages?

Thanks

Fezz

[powerrodsmike]

Do it all at once if you can. add the minimum amount of catalyst that is required for you temp range, or do it first thing in the morning when it is cool. It will give you more working time.

do 3 or 4 layers of 1 1/2 oz matt, roll it out tight and you will build about 1/8 to 3/16" thickness.
later, mikey