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Technical Tech Week: Build your own recessed firewall

Discussion in 'The Hokey Ass Message Board' started by rockable, May 10, 2021.

  1. rockable
    Joined: Dec 21, 2009
    Posts: 4,428

    rockable
    ALLIANCE MEMBER

    firewall 10.jpg

    I knew I was going to have to have a recessed firewall in my 34 Ford and I didn't like the looks of any of the aftermarket options that I saw. Plus, they were approx. $400 including shipping. So, I decided to make my own. I bought a piece of 16 gauge sheet metal for $18 off the drop pile at my nearby Alro Steel. From there, all I have invested is labor and some consumables.

    I know what you're thinking. You're thinking, I don't have the necessary shears, brake, bead roller, etc. Well, I have all that stuff but it really wasn't going to work well to use them. So, I basically used two pieces of angle iron, some clamps, hammers, grinding and sanding discs and my welder. That's it.

    First, you MUST make a pattern. It's a lot easier if you do and poster paper is cheaper than steel and easier to cut and fold. Make a pattern like this. Establish your center line and make all measurements from the center line. That way the firewall stays symmetrical. I designed mine so that I would have as many butt welds as possible. Try to keep welding on corners to a minimum.

    After drawing it out, cut it out and clamp it in place. See if you need to make any adjustments and, if you do, make them and retest the fit. I decided to leave the top portion of the firewall in place because it has nice bead work in it. I also decided I would use the two X patterns out of the original firewall to fill the center. My bead roller won't roll 1" beads in 16 gauge and yours probably won't either.
    Pattern.jpg
    Pattern 2.jpg

    After you have a good working pattern, trace it out on the sheet metal. Clean the sheet metal with solvent before you break out your new Sharpie. Otherwise, the grease will just mess up your Sharpie and your layout. Once you have the layout, cut it out. I opted for an old Black and Decker saber saw that I've had for years with an 18 tpi blade. it was a lot easier than using shears and it didn't distort the metal.

    Firewall 4.jpg

    After cutting it out, mark all the break lines on the correct side of the sheet metal. Then, using two pieces of angle iron and some clamps, make yourself a sheet metal brake. Be sure to use stout clamps and get them good and tight. Otherwise the metal will slip and you don't want that. Once you have it clamped up tight, use a hammer of your choice to bend the metal in the correct direction. Your pattern should tell you which way to go.

    firewall 5.jpg

    It you did it right, it should look something like this. You will notice the two upper corners will need to be filled with small squares of 16 ga. and there is one corner on each side that you will have to weld.

    Now, it's gut check time because you have to cut out the old firewall before you can put this one in. Drill out the spotwelds in the ends and get out the Ziz wheel to make your cut along the top side.
    firewall 11.jpg

    After removing the side pieces, it's time for a test fit. Hopefully, yours looks like this. The little butt weld clamps you buy at Harbor Frt. work well for clamping the top weld joint. Just take them out immediately after tacking. The weld shrinks and they can be difficult to remove but they are just going to get worse if you weld more.

    firewall 1w.jpg

    From there on, it's just a lot of welding and grinding. Don't get too anxious and try to do all your welding at once. Skip around and keep things from getting hot. Grind the tops off the welds and hammer on dolly to stretch them back out before applying the next tacks. Once you're done, finish sanding the welds and hopefully yours is nice and smooth and will only require a skim coat of filler to finish it off.

    firewall13.jpg
    firewall 6.jpg

    From here, I will have to trim out a radius for the transmission once I get to that stage. Then the floor and transmission tunnel will need to be fabricated. Before I can do that, I have to take the car off the frame and rework the X member first to accommodate my automatic transmission. The standard X member is just not wide enough in the middle. So, there you have it. Good luck!
     

    Attached Files:

  2. KJSR
    Joined: Mar 7, 2008
    Posts: 2,494

    KJSR
    Member
    from Utah
    1. Utah HAMBers

    Nice write up!
     
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  3. Looks pretty good to me.
     
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  4. SPEC
    Joined: Feb 1, 2021
    Posts: 811

    SPEC
    Member

    Good job.
     
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  5. rockable
    Joined: Dec 21, 2009
    Posts: 4,428

    rockable
    ALLIANCE MEMBER

    Here is how you use 2 pieces of angle iron to bend the flanges. Make sure you have it tightly clamped and don't thin the metal. Just hit it enough to bend it, then tap it down.
    0510211541a.jpg 0510211541.jpg
     
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  6. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,717

    1971BB427
    Member
    from Oregon

    My engine bay is way to small to build a recessed firewall when I removed the flathead 4 cyl. and put the V8 in my car. Plus it had two footwells that were about 14" deep and the old 4 cyl. set between them. So I cut the whole firewall out and bought 10 ga. metal to make a new firewall out of. I started by making a cardboard template to fit the body, and then laid it out on the new steel. Then marked it out and took it to a local sheet metal shop to have him plasma cut it out. I also had him cut about 12" out of the middle, and shear me two strips about 3" wide so I could build a distributor offset into the new firewall.
    I welded in the two halves on each side, and then welded up the offset, and welded it into the firewall as one piece. Gave me just enough room to cram the SBC into my little Austin's engine bay. Still no room for a fan, so it has a pusher fan in front of the radiator that's the only way it all fit.

    [​IMG]
     
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  7. rockable
    Joined: Dec 21, 2009
    Posts: 4,428

    rockable
    ALLIANCE MEMBER

    I got a few likes but hardly any replies (which keeps the thread alive), so I will do one bump since tech week is finishing up.
     
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  8. loudbang
    Joined: Jul 23, 2013
    Posts: 40,276

    loudbang
    Member

    Well I will add one to this neat thread. :)
     
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  9. hemihotrod66
    Joined: May 5, 2019
    Posts: 968

    hemihotrod66
    Member

    Mine is flat... Needed the room...
     

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  10. rockable
    Joined: Dec 21, 2009
    Posts: 4,428

    rockable
    ALLIANCE MEMBER

    That is a big engine, for sure! You needed stretchers, didn't you?
     
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  11. WB69
    Joined: Dec 7, 2008
    Posts: 1,958

    WB69
    Member
    from Kansas

    Looks good to me! Good tech thread.
     
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  12. Blues4U
    Joined: Oct 1, 2015
    Posts: 7,589

    Blues4U
    Member
    from So Cal

    Nice write up, thank you!
     
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  13. rockable
    Joined: Dec 21, 2009
    Posts: 4,428

    rockable
    ALLIANCE MEMBER

    Thanks guys. I appreciate all the likes. Doesn't seem like many people are voting for their favorite. Link is at top of page 1.
     
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  14. Onemansjunk
    Joined: Nov 30, 2008
    Posts: 318

    Onemansjunk
    Member
    from Modesto,CA

    Here’s what I’m in the process of doing. I let the new firewall run down to the frame to act as HEAT SHIELDS and to make new body mounts as well. I welded up the hinge holes and in the process of applying body filler to the rough spots to give it that Smooth Sex Appeal. I also filled some rust holes behind the Upper hinge supports with pieces of a old barbecue I found on the side of the road. Made of 16 gauge.[​IMG][​IMG][​IMG]


    Sent from my iPad using The H.A.M.B. mobile app
     
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  15. Dave G in Gansevoort
    Joined: Mar 28, 2019
    Posts: 2,598

    Dave G in Gansevoort
    Member
    from Upstate NY

    Many decades ago, I stuffed a 327 in a 62 CJ5 (hey at least the years fit right???).

    Cut the firewall to clear the engine, didn't have a clue how to fold afirewall like you guys have beautifully done.

    What to do? In the local hardware store, saw an inexpensive stamped sheetmetal wheelbarrow. Viola, firewall! Rigid enough to not warp too bad, deep enough to clear the engine, and only required triming to fit, and gas welded it in (my first time doing anything other than practicing...). Sorry I was 18 at the time and pictures were the furthest thing from my mind...
     
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  16. Since we have not done a Tech Week in a LONG time a lot of these newbies aren't getting it. Used to be a very big thing. Wish I could contribute but the only thing I have going right now is trimming house windows out with reclaimed bug pine ;)
     
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  17. terry k
    Joined: Jan 8, 2007
    Posts: 6,546

    terry k
    ALLIANCE MEMBER
    from toledo oh

    Looks good. I'm also doing a '34 5w. Like your ideas.
     
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  18. vtx1800
    Joined: Oct 4, 2009
    Posts: 1,709

    vtx1800
    ALLIANCE MEMBER

    Nice job!!
     
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  19. lippy
    Joined: Sep 27, 2006
    Posts: 6,825

    lippy
    Member
    from Ks

    To clear a distributor, I've use baking pans from the local grocery store. Just buy the good baking pans. lol
     
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