Rear Firewall

[AZPete]

The 818 kit includes two 1/8"panels for the seat side of the rear firewall and that's all that is necessary for a basic build, but I wanted to hide the fuel tank and wiring from the engine side so I added an engine-side firewall.
I bought a Boyd fuel tank and modified the seat-side pieces to move the driver seat as far back as possible. I had the upper panel bent an additional 20 degrees and even cut out 2 squares for the Boyd tank mounts to save 1/4". There is thin foam between these panels and the tank.
http://i210.photobucket.com/albums/bb180/AZPeteCobra/Rearfirewall-seatside.jpg (http://s210.photobucket.com/user/AZPeteCobra/media/Rearfirewall-seatside.jpg.html)


For the engine side, it's best to do this BEFORE you put the engine in! I wasn't that smart. But, you'll want to make it removable so read on.
For the engine side of the rear firewall I cut and riveted in a rectangle for the bottom between the engine and fuel tank. This was riveted because if I need to remove the tank I can do it from the seat side. Insulation added before riveting.

For the upper portion, I cut a 16" x 50" cardboard piece but then found I could not get it in place between the side frame pieces and the trailing arms, even from the bottom. I then cut three pieces - each with 1-inch 90-degree tabs at the bottom - so I could access the bottom mounts of each panel from the seat side. Here's a photo showing the middle triangle piece in place and the left outer piece removed for wiring work. Since the engine was in there was not enough room to drill holes so I drilled 1/4" holes from the seat side and installed #10 rivnuts in the holes from the engine side. Lesson learned: it can be done but it's much easier before dropping the engine in.
http://i210.photobucket.com/albums/bb180/AZPeteCobra/Rearfirewall-partial.jpg (http://s210.photobucket.com/user/AZPeteCobra/media/Rearfirewall-partial.jpg.html)

http://i210.photobucket.com/albums/bb180/AZPeteCobra/Rearfirewall-outerpanels.jpg (http://s210.photobucket.com/user/AZPeteCobra/media/Rearfirewall-outerpanels.jpg.html)

[Goldwing]

I wanted to add this too, but got so eager to drop the engine in, I forgot too, lol. I wanted the secondary firewall as much for sound control as safety. Sure, in an open top roadster, the extra firewall won't be doing much for noise abatement, but long term, some sort of top is planned. I'll appreciate the efforts then.

[bompus]

Thanks for posting the info up and showing it off in-person. It really does look nice in person and will save me the same headache of trying to fit in a single piece and instead I am planning on going with your easier multi piece approach. From what I saw in person ( thanks again! ) , it looked like the inner-most angles of the two side pieces were sharing some of the rivnuts ( using a washer ) from the sides of the center piece. If you had to do it again with the engine out, would you take the same approach?

[AZPete]

Aaron, next time I'd do it the same but before putting the engine in. Then I'd be able to drill holes in exactly the correct places! With the engine in I had to drill holes from the other side so I missed the mark on some. Fortunately some larger washers will hold some edges and cover my mistake. Don't tell anybody, eh?

It was nice meeting you. I regret that my build is in the ugly stage covered in wires, but I trust you saw Jerome's beautiful work after you left.

[svanlare]

Thanks for posting Pete. My donor should show up this week and my kit in the next 2 so the timing is a perfect reminder as I start setting up the garage and panelling.
-Steve

[07FIREBLADE]

What thickness are you guys using to make the firewall?

[wallace18]

I used 14 ga. aluminum.

26749

[RM1SepEx]

I'm going to use 20 ga... .032 about 1/2 as thick. I just want to clean it up and keep engine and header heat away from the gas tank

[K3LAG]

I used .063 (1/16") and only covered the bottom portion.

Larry

[FFRSpec72]

Seems to me that the engine firewall can be done as 1 piece (installed with engine out) and that the cockpit firewall should be made removable (done with rivnuts)

[bompus]

What if you need to get access to the front of the engine easily? It would probably be quite the pain to get the non-removable 1-piece out unless you just planned on pulling the engine out completely.

[RM1SepEx]

As an 818 builder that messed up a water pump gasket... you NEED the engine side firewall to be removable. I was able to pull the timing belt etc and water pump through the cockpit, over the stock gas tank. If the tank is taller, the crank bolt will be a problem.

As an early builder (# 17 first start 11/1/13) I did not put an engine side firewall in. I will be doing it soon, it will be in pieces and will have nutserts and silicone holding on the .032 aluminum sheet(s) as it will be in pieces.

[wleehendrick]

I have the Boyd tank lize Pete. Iinstalled, it goes no higher then the lower frame tube. I'm putting riveted firewall in on the lower portion, like him, to keep heat off the tank. I may also put a removable panel in the upper section(s)... still undecided, but need to make up my mind before I install the motor!