Author Topic: Firewall options  (Read 2436 times)

Offline jon316

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Firewall options
« on: August 29, 2019, 08:33:33 PM »
Hey guys, got a 82 that has a very iffy firewall. Looks like it was repaired a bit with por15 but the more I poked and scraped the worse things got. The rest of the truck is super solid which is crazy. Aside from the foot wells. Looks like it had a water issue I suppose from being parked?

I’ve been searching for some panels but only find ones for the sides. Really didn’t want to tear the front end apart but looks like I may have to.


Any ideas? I’m working on having a buddy of my fathers that does sheet metal and works on these older cars to come look at it and perhaps just cut and fabricate a piece in, but I know that can be hectic especially with everything still on.


Pictures below:



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Offline DanMcG

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Re: Firewall options
« Reply #1 on: August 30, 2019, 03:56:33 AM »
I've never seen panels for what you need. The only good fix will be fabricating your own and welding them in.

Offline jon316

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Re: Firewall options
« Reply #2 on: August 30, 2019, 07:38:11 AM »
Yea best bet is gonna be take that whole front end apart and strip the firewall huh? No escaping it. So caught up on cab corners and bed being rust free didn’t think anything of that small crack on firewall!


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Offline JohnnyPopper

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Re: Firewall options
« Reply #3 on: August 30, 2019, 12:48:22 PM »
Wow, never seen that area rust either, some corrosive crap came in from the vent and sat there wet.

Don't know if you have to remove the front end though it would be alot easier.

Can you find a donor and weld some patches? I would...  ::)
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline VileZambonie

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Re: Firewall options
« Reply #4 on: August 30, 2019, 06:40:06 PM »
Good excuse to build a nice firewall. I made one myself and it came out beautiful. It's a lot of work but if you love your truck and don't want to look at that mess....
,                           ___ 
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              ⌠¯¯¯¯¯'   [☼===☼]
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline roundhouse

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Re: Firewall options
« Reply #5 on: September 01, 2019, 03:16:14 AM »
Fixing it right would require pulling the engine and using a replacement cut from a donor truck

Depends on how nice you want it

If it’s just a daily driver
I’d pressure wash and steam clean it and scrape all the sound deadner off

Brush on some rust stopper chemical and cover it back up with some spray on undercoating

Offline jon316

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Re: Firewall options
« Reply #6 on: September 01, 2019, 08:06:38 AM »
Fixing it right would require pulling the engine and using a replacement cut from a donor truck

Depends on how nice you want it

If it’s just a daily driver
I’d pressure wash and steam clean it and scrape all the sound deadner off

Brush on some rust stopper chemical and cover it back up with some spray on undercoating


Yea but then it still leaves the hole there for water to fall over the engine. It’s not a show truck and I don’t even plan to paint the thing just a fun weekend truck to also move garbage and stuff in the bed around house. So trying to do least as possible.

As for donors they’re almost impossible to find here in south Florida. Unless i want to over spend that is.


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Offline roundhouse

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Re: Firewall options
« Reply #7 on: September 03, 2019, 08:44:26 AM »
I’m suggesting cutting a patch panel and using  some good urethane caulk to glue it over the hole and spray some bedliner undercoating over that to help hide it

The pics are not loading for me so I can’t see the actual problem
But I’ve done a lot of that kind of “Appalachian American “ (we dont like being called hillbilly’s anymore )
Repair’s before to keep water out of an old vehicle

Offline jetmech

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Re: Firewall options
« Reply #8 on: September 24, 2019, 08:44:09 AM »
I have seen this failure quite a bit even here in Texas. It is caused by cracking and drying of the globs of sealant the factory put in the seam in the cowl vent area. I always try to clean and reseal that seam from inside the cowl vent. Not easy to get to and not really possible to do a great job. I cut patches from a firewall and weld them in but it would be a good chance to fab a custom firewall.
'86 Sub and '86 SWB C-10
1990 454 SS

Offline jon316

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Re: Firewall options
« Reply #9 on: September 28, 2019, 02:57:45 PM »
Been busy working like crazy but was able to remove door sills the carpet and the ac box to make room for fabricator to work. It’s a friend of my fathers and he says he can fix it so let’s see. I got all the panels already even can corners getting replaced even tho they’re probably saveable. I’ll see what fabricator does. The ac box was filled with that spray foam, probably made it worse considering it probably wasn’t draining properly and just concentrated the rust. It’s insane how solid this truck is yet how obliterated with rust it is at the same time!! Lol.


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Offline JohnnyPopper

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Re: Firewall options
« Reply #10 on: September 29, 2019, 04:25:09 PM »
Nice work Jon, looks like it may be worth it after all!

Can someone tell us why GM used such godawful and probably toxic black sealer? AND why they were so sloppy in application?

Never mind...for mine "it was the '70s" is the only logical answer...
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline jon316

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Re: Firewall options
« Reply #11 on: September 29, 2019, 04:27:45 PM »
Nice work Jon, looks like it may be worth it after all!

Can someone tell us why GM used such godawful and probably toxic black sealer? AND why they were so sloppy in application?

Never mind...for mine "it was the '70s" is the only logical answer...


I agree, and the cowl design was not very good considering they barely welded the metal together at firewall and put that black sealer you speak of. Just gave room for water to sit! But dang nothing like a square body either! This is my second one, my first one being 17 yrs old. I’ve had several OBS squares 88-97 so rust what never a major issue with my builds. This one I was hoping to keep for quite some time so definitely gonna try my best to make that firewall last!


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