Bond DSE fill panel, should I cut out the firewall behind?

[Rileys68Camaro]

I'm planning to bond in my DSE firewall panel, and was wondering if I should cut out the firewall behind where it will go? I'll be using 3M panel bond, or maybe Fusor. If I Cleko rivet it for clamping, what do I fill those holes with?

One thought is that way I could paint and seal it from the inside easier and more thoroughly, the other thought is it would be stronger to leave the existing firewall intact but I'd have small holes and the A/C cutout to hold crud in and I'd only be able to seam seal it from outside.

Car is a factory A/C car, with an poorly installed Vintage Air Sure Fit system that's getting altered so I can smooth up the firewall at touch.

Access to the tools and supplies to weld it are pretty slim, not to mention the mess and prep, so I'm going to bond it and paint it and I think it should be fine.

Please let me know if I'm in the wrong.

[MrQuick]

most leave it in cause it adds rigidity to the panel. I like to cut them out, but its just my personal preference.

vince

[elitecustombody]

after clecos removed ,bevel the edges of the holes with bigger bit and use same bonding adhesive to fill the holes, not the best solution,but you won't have much choice,I'd cut off old firewall too

[dhutton]

I think they might rattle against each other. The heater core lip is quite close to the fill panel when it is installed if I remember right.

[GM Muscle]

i think you should leave the old firewal behind it. as long as you put some panel bond/auto foam between the two panels you should be fine. they do it in door skins on flimsy new cars all the time. i would aslo attempt to find a welder and put a few spot welds in the center of the new panel where you the old firewall touches it just to keep it all in place. then you would only have to fill a few spots with putty. just think it through and takle it. half the battle is getting started..

[jake8092]

I just welded mine up last night. I welded over the OEM firewall. I can see where vibration would be a major issue and a PITA so I drilled holes in the new delete plate and slug welded anywhere that i would not be able to weld from inside the cab ie. A/C cut out, misc bolt holes...After all of that it's very rigid and after beating it nearly to death I dont think it's going to make too much racket! :fingersx: