A couple questions about Fiberglass in general....

[spoonraker 10+ year member]

Just take it to a shop and pay somebody to do it properly. A firewall isn't something you want to experiment on.

 

[CJL 10+ year member]

Fiberglass does not bond to metal, and fiberglass should never be used to repair metal surfaces.
Metal expands and contracts when it heats up and cools down, fiberglass does, however they do so at different rates. With something like your firewall that is subjected routinely to extreme heat, it would not be wise to try to patch it with anything other than metal. Plus while fiberglass may be strong, it does not have the heat absorbing properties that metal does, that is why firewalls aren't ever made of anything except metal.

Never thought of that...Good info.

too bad it wasnt rusting out in the back then you could just do a blowthrough

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hammer it in to shape.

Oh ok..For some reason i was thinking you was talking about thicker metal