Firewall: to swap or not to swap?

[jrdecat]

In reading pages and pages of threads of countless projects and builds I notice that there are usually several ways of accomplishing the same task.

Specifically, some people prefer to cut the firewall from a donor and patch it into the new cab, while others prefer to fill every hole on the new cab and then mount components as needed.

My project is a 53 GMC 5 window cab dump truck that will eventually sit on an 86 K10 frame and using the 5.7/auto tras combo. I bought the dump truck because it had a great cab and it has the bigger, wider fenders for a full size frame.

I'm just curious...with YOUR project, which method did you choose and why?

[lv2tri2]

Cut original firewall complete, replaced with aftermarket. My decision was necessary due to the condition of the original. It had been split in the junk yard.

[e015475]

I have a front suspension with rear-steer rack and pinion (Jaguar) and rather than modify the oil pan, I pushed the engine back a little. It is a 5.3 LS. With the stock firewall the valve covers would hit the edges of the stock 'doghouse'.

My first thought was to buy an aftermarket firewall, but I didn't care much for the aesthetics.

I'd heard of guys buying a steel wheelbarrow - don't laugh - and cutting it up to use as a wider doghouse. I'd seen this done and it looked good!

As far as filling holes, the guy doing the metalwork on my truck said it'd take him about the same time to fill the holes as to fab a new firewall. Here's what it looks like today (sorry to anybody that's already seen this on my build thread or other sites- seems to be a pretty common topic)



This firewall is make from flat stock on a bead roller and spot welded into place where the factory one came out. The factory 'hat' sections inside the cab were salvaged and reinstalled as well as a new reinforcement that ran horizontally from one side of the cab to the other

And from the inside

[Dan in Pasadena]

Mine's a '55.2 TF.

I literally stopped counting the holes after FIFTY! Filled them all. I wanted the factory embossing and it'll have nothing mounted on it.

LOTS of welding? Yeah, but cutting out and replacing the entire thing is more work.

[mr48chev]

I'm like Dan in that respect, I want the factory look of the firewall with the holes filled.

The wheelbarrow trick works pretty good, my buddy did that on his 29 Model A roadster which was the first one I had seen and I've seen several since. You just have to hunt around to find the right little garden wheelbarrow with the right shape.

[my56chevytruck]

I wasn't into cutting my firewall out, I wanted to maintain the original stability of it. I Made a cardboard template of the firewall and laid it over a new sheet of steel. I believe it was 18 gauge. I cut it out, and welded over the original one. I felt this was the strongest way, and then cut out my holes for brakes and steering column.

[Flysocal]

I filled all the holes. I like the look of the original firewall and inner fenders. It's nice to retain original features when possible. If you do a custom firewall you can seat the engine back a couple inches to gain radiator clearance and move some weight back. I like idea and if I had to do things over again that would probably make the most sense. It is tight as hell in the original engine compartment but I made it work.

[Miller197]

Im another +1 for welding the holes up

Takes a while but its the most inexpensive way around it

[b-mac]

e0, that thing is beautiful.

I filled the holes. Guess I wanted to retain the factory look and I didn't have a bead roller at the time either.
Once I got everything mounted, the rear of the LS was too close to the firewall. Some have used a big hammer to solve this problem. I cut in a couple of recesses into the firewall.
You can see them in this ugly pic from the inside.

[vintovka]

Nearing end of 54 on a k10 project. If aftermarket firewalls are like aftermarket fenders i would steer clear. Better to patch/plug old one if it fits ok. Would sooner see a whole stainless firewall cover if patching is a problem. If its not a show truck the firewall appearance seems a secondary issue as most just seem to look at the engine anyway.

[lv2tri2]

An ugly firewall ruins anything else under the hood

[67GMCkid]

I put a repop firewall in mine and would do it again and wouldn't have think twice about it.

The only thing I noticed with mine was the pass side under dash brace that is welded to the inside of firewall was about 3/4" to the left of where the factory one I removed was so I had to drill 2 new holes to plug weld it to the cowl...

I think it looks so much better now looking into the engine compartment and seeing the factory style flanged seams between the firewall and floorboards..

Well worth the extra few hours labor and several hundred $$ in my opinion..

[Khaus]

Firewall, toe boars and upper cowl from LS Fab. Can be purchased individually or as a complete set for $300usd.

[mr48chev]

I'm not sure exactly when you made the first firewalls but I think Jrdecat's original post was made before any of us knew about them. Before that we did it the hard way.

I'm shooting for everything on my 49 to look like it was or "could have been" customized in the late 50's. Partially to honor the cool customs that I saw when I was just turning into a teenager and To have it be timeless rather than with distinct trick of the week mods that date newer builds severely.

[dsraven]

if welding the holes, look into welders series for their "unholes". buy a pack of same sized ones and then drill the holes in the firewall to fit that size. use a step drill for a nice clean and uniformly round hole that the plug will fit into. then you can use a magnet on the back side to keep the "unhole" in the right spot and flush with the firewall while you spot it in place. leave a little space all around the plug for the weld to penetrate well. a magnet will distort the welding so just spot them in then remove the magnet and use a flap disc to smooth the tack out. then weld a 1/4 of the perimeter and planish, while still smoking hot, with a hammer and dolly. this will help the area cool and not distort. go to the next hole on the other side of the firewall and do the same. move around a bunch to keep the heat down in any one spot. I have heard of guys using electrical box plugs but they are usually plated or painted so that involves a bunch more work. if you have a fab shop close by you could ask if they have any punch outs from their punch press but welders series are pretty cheap. Canadian money so the USD buys more for less right now.
I have heard of guys using autobody panel adhesive to glue a new panel over the old one as well.
if cutting the old one out ensure to brace the cab in an X configuration in the area so things don't move/shift/sag when the firewall is out or the new one is welded back in.

[Dan in Pasadena]

Just in case anyone still hasn't decided how to do theirs and wants a cheap fast way - here's the trick. I saw a guy make one of these himself from metal but this is ready to go and when I saw it (years ago) it looked good. Not noticeable.

http://nolimit.net/products#!/Smooth...tegory=6157546

[my56chevytruck]

Originally Posted by jrdecat

In reading pages and pages of threads of countless projects and builds I notice that there are usually several ways of accomplishing the same task.

Specifically, some people prefer to cut the firewall from a donor and patch it into the new cab, while others prefer to fill every hole on the new cab and then mount components as needed.

My project is a 53 GMC 5 window cab dump truck that will eventually sit on an 86 K10 frame and using the 5.7/auto tras combo. I bought the dump truck because it had a great cab and it has the bigger, wider fenders for a full size frame.

I'm just curious...with YOUR project, which method did you choose and why?

Like you said, there are several ways to make something different. I chose to remove the old firewall, get your cardboard out and make the template to replace the entire one with flat stock.

[jweb]

I just used 2 flat pieces to replace the sections where the most holes were.
I do like the factory look better, but it can be a problem if you're using a firewall mounted brake booster.