Firewall Build

I decided that the firewall needed to be made in several pieces. I want there to be a steel main wall - closest to the engine. Then there will be come kind of sound and heat block sandwiched between an inner wall that might be made out of fiberglass. That's to be determined. Today it was time to tackle the main wall.

I used sheets of 13 gauge sheet steel to make the base of the inner wall. Since the heater hose will protrude a little bit into the passenger compartment I decided to make the main wall in a way as to let the hose end up where it needs to be. First I tackled the easy part of the main wall - the pieces that surround the center part of the Coyote engine.

I used the roll cage as a guide for the shape of the wall itself. I cut one piece of sheet steel to fit and used a mirror image to make the other side. I left open the center third of the firewall for a later time. This will be the part that allows for the radiator hose to poke forward and will be the section of the firewall that will be removable for access to the front of the engine.

I found a really great piece of scrap metal at the metal yard that made mounting the sheet steel so much easier to the roll cage. I used a piece of metal that was made to make track for sliding glass doors. I was able to weld this metal onto the bottom of the roll cage to give me a mounting point for the sheet steel. Then I placed a few of 1/8 x 1" metal braces. Here's a shot of the bracing in place.

Here's a closeup shot of the mounting system I put on the roll cage.

  I then laid up the sheet steel against the mounting points to see what it looks like. Here's a shot of the wall almost in place.

You can see the opening I left. This will be covered with the same 13ga sheet steel that will be made to allow the radiator hose to stick into the passenger compartment just a bit. That part of the build will come later.

I haven't decided how I'm going to attach the sheet steel to the mounting points as of yet. I'll cover that next when I decide what will work best. I'm thinking that I want to be able to remove the entire wall when needed. So, I'm sure I'll use some kind of multiple thread based fastener. More on that later.

Next I worked to close up the corners at the base of the firewall. I decided to attach the same 13 gauge sheet steel cut to size at the base of the firewall and bend a 90 lip to give the flat firewall another mounting point for the firewall. Here's what it looks like.

Then there is the big hole where the radiator hose will protrude into the passenger compartment. I want this piece to be able to be removed to give access into the engine space. I started by bending a piece of 13 gauge sheet steel to give me the basic shape needed to cover the radiator hose. I left plenty of room in the bend to allow me to work with the hose as it bends down towards the connection for the front radiator. Here's a shot of the first piece of sheet steel I worked with for this project.

Once I had the basic shape it was just a matter of getting it all to blend in. It took 4 more pieces of metal on each side to close up the hole. I cut and bent one piece at a time. When I had the piece just right I then made a mirror copy to close up the other side. Here's a step by step progression of how it was made.

Each piece was tacked. I welded the entire piece up. It kind of looks a bit like the Iron-man mask right now. After a little grinding and shaping it will look pretty amazing.

It took a while to get back on this project but here we go. I decided it was time to start working on the inner fire wall. Problem was I just didn't like how far I allowed the piece above to protrude into the passenger compartment. I did a bunch of measurements and found that I could cut it way down. Here's a shot of the part shown above as it looks now.

You can see that I have cut a hole into the outer firewall to allow the shifter linkage to operate freely. I will secure the grommet at some future point. I really like how the new engine cover looks now. It pokes a lot less into the passenger compartment. Now it was time to turn my attention to the inner firewall.

I decided to use a piece of 3/16 plywood as the base for my inner firewall. I figured that I wanted something easy to work with and light weight for this part of the car. Since I would be bonding carpet to this part of the firewall I decided that I wouldn't need such a rigid structure as was needed for the outer wall.

I made a template out of cardboard to allow me to make my cuts for the left and right side of the firewall. Once transferred onto the plywood it was an easy matter of cutting until it fit tightly into place. I then worked to cut out the center section where the outer firewall protrudes into the passenger compartment. After a few cuts I had it just right. Since I plan to add a layer of fiber glass to the passenger side of the inner firewall I knew I would be able to shape something to fit around the protrusion of the outer firewall.

To get the shape right I resorted to using duct tape to allow me to lay down the fiberglass onto the plywood where the outer wall sticks past the inner one. I used a piece of plywood to give me an air gap between the inner wall and the outer wall on the protrusion. With the wood in place I simply added strips of duct tape until the general shape was what I wanted it to be. Here' a couple pictures showing the inner wall ready for glass.

Now it was time to lay a couple layers of fiberglass over where the protrusion is. Here's what it looked like when that step was completed.

Once it dried I took the inner firewall out of the car and removed the tape and wood from the back of the fiberglass. Once removed I was surprised how flimsy this patch felt. I was hoping that as I glassed the rest of the firewall that it would stiffen up, and that's exactly what it did.

The next step was to lay down two layers over the entire length of the inner firewall. It took a lot of resin to cover this thing but the result was well worth the material needed. Finally I decided to add some bondo to smooth out the entire assembly. The result was really nice. Here's a finished shot of the smoothed inner firewall.

Next I will figure out how to mount the inner firewall to the car. I plan to use some sound deadening material in between the inner and outer wall. That will be installed at a later date. I think the mounting will be pretty straight forward. I want to use some kind of channel along the bottom of the fire wall to hold it in place and use some kind of quick on/off kind of fastener along the sides and top. I want to be able to remove the inner wall with little trouble. More to come on how I choose to fasten it all in place.

OK I figured out how to mount the inner firewall to the car. I used a couple pieces of angled steel I had laying around and mounted it to the bottom of the car to give me channel where the inner firewall could be locked into place. Here's a couple shots of the channel I made.

The channel is just wide enough to allow the inner firewall to slide into it. At the top of the firewall will be 4-6 screws holding the inner firewall to the outer structure. This should hold everything solidly in place while making it easy to remove the assembly when I need to get to the front of the engine. Here's a shot of how the inner firewall looks in place.

As with most things that are made by hand, there is always another way. I decided to take a second look at how to make my firewall easier to take in and out of the car. Since front end of the engine will need to be accessed for maintenance, something had to be done. The way I attached the fire wall just wasn't easy enough for me to take in and out. So, time for some rework.

I took apart all the panels and tacked up a bunch of tabs to all the bracing attached to the roll cage. The tabs were then drilled and a 1/4-20 nut-cert was used to make installation of the panels so much easier. The two big side panels have 5 bolts each holding them in place. The small panel at the bottom, I left with nut/bolt connectors. It is easy enough to remove this panel after the large ones are out of the way.

After getting the large side panels to install easily, I took a second look at the piece I made to cover the front of the engine that protrudes into the passenger cabin. It was way too heavy and just didn't fit right. I decided to scrap it and start over. The panel I made fits much better. welded up 4 tabs with 1/4-20 nut certs to hold this panel in place. I can now remove the entire internal firewall in just a few minutes. So much better now.

The inner firewall is still usable. All I did with this was to determine where I wanted to attach external to the internal fire wall and to add spacers to allow the internal firewall to sit just were I want it when screwed down.

Finally, I purchased some fire resistant caulk and sealed up all the cracks and openings around the firewall panels. I purchased sound and heat barrier from Amazon. Here's the material I used.

uxcell 394mil 16.36sqft Car Noise Sound Deadener Deadening Insulation Mat Waterproof and Moistureproof 60" x 40"

This stuff is really easy to work with. Just cut it to size, remove the backing and stick it to the surface. It really stays in place. I'm even thinking with a little heat from the engine and it will stick even better.

The last thing I did was to take care of the air gap at the top of the roll cage. There was a very small gap between the top of the roll cage and the roof. To close this up, I used a can of "RightStuff". That's the material used to seal up gaps in home construction. It comes out in a super sticky form that expands to fill gaps.

I allowed the material to cure for 24 hours and came back with a knife to trip the excess. When it was the general shape I wanted, I added two layers of fiberglass on top. Now the roll cage is basically bonded to the roof. I will bondo and sand this area to give it a more finished look. With a little paint it should look really good.

Now, I think the fire wall is about complete. Still a little finish work required and carpet to be placed on the inner firewall. For now the pictures below show how it looks both with the inner wall in place and removed.

Here's a shot of with the inner wall removed. Notice the sound deadening material and how well the new center panel fits. The new design makes disassembly of the inner wall so much easier. 

Here's a shot with the inner wall in place. Notice the four mounting screws. They will go on top of the carpet and will blend in to the black carpeting that I hope to use for finishing off the exterior.