Firewall Patch????

[DA4AD]

I have to patch a hole in a firewall. It is about 6" in diameter.
Should I cut the patch the same size as the hole or should I have a 1/2" of overlap and crimp the edge all around?
I think a patch of the same size would make a cleaner repair but may be a little harder to weld.
Suggestions?

 

[DusTed74]

Make it the same size. Take you time and make it as tight a fit as you can.
If it's possible, weld it from the inside and have someone hold a piece of aluminum or copper against the area where you're going to weld. This way your weld comes out flat and there's less time grinding.
Ted

 

[DA4AD]

Thanks Ted, never thought of welding it in from the backside.
Good idea.