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Thread: firewall install feedback

  1. #1
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    firewall install feedback

    i don't have the body yet as i purchased the stage 1 kit.

    i tried to square up the firewall as best as possible. the upper and sides are equidistant from the frame.

    there are however some gaps where the foot box lines up with the firewall

    i wanted to see if anyone had advise before i drilled the sheet metal

    i am planning to use 1/4" - 20 button head screws instead of rivets. i figured id rather spend time tapping than drilling out rivets

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    Senior Member FF33rod's Avatar
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    The only thing concerning to me is the last pic - need to be able to get all the pieces to butt up against each other. I had to do a little grinding of the frame; welds were not allowing the pieces to sit flat and didn't allow them to come together in the right places. Looks like you've got the "level" part setup well... Those are my comments as a fairly new builder...

    Steve
    Gen 1 '33 Hot Rod #1104
    347 with Holley Sniper & Hyperspark, TKO600, hydraulic clutch, IRS, Foose 18" Wheels, 245 & 315 BF Goodrich G-Force Rival S tires, DRL, power windows, roadster & hard top, Digital Guard Dog Ignition

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    Seasoned Citizen NAZ's Avatar
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    I had to relieve some areas around the welds to get a good fit. I used a die grinder and flapper wheel to put a large steep chamfer on the back side of the firewall so the weld didn't interfere, that left the front side with the original size hole and tight fit around the tubing.

    Also, I used 10-32 screws (1/4" is rather large) as the fine thread gives me more thread engagement than a course thread. 1/4" fasteners in any thread pitch will have very little thread engagement.
    33 Hot Rod Super Pro Drag Racer
    33 HR NHRA Cert Roll Cage Build

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    Quote Originally Posted by NAZ View Post
    I had to relieve some areas around the welds to get a good fit. I used a die grinder and flapper wheel to put a large steep chamfer on the back side of the firewall so the weld didn't interfere, that left the front side with the original size hole and tight fit around the tubing.

    Also, I used 10-32 screws (1/4" is rather large) as the fine thread gives me more thread engagement than a course thread. 1/4" fasteners in any thread pitch will have very little thread engagement.
    thanks for the feedback on the screw size. thats a good point about thread engagement.

  5. #5
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    Quote Originally Posted by FF33rod View Post
    The only thing concerning to me is the last pic - need to be able to get all the pieces to butt up against each other. I had to do a little grinding of the frame; welds were not allowing the pieces to sit flat and didn't allow them to come together in the right places. Looks like you've got the "level" part setup well... Those are my comments as a fairly new builder...

    Steve
    thanks i had the same concerns i hand filed all the joints and openings need to spend more time on the passengers side foot box

  6. #6
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    Check out my post at
    https://thefactoryfiveforum.com/show...l=1#post373716

    Maybe those pictures will help.
    - Peter

    Peterh226. #1134
    '33 Hot Rod 2nd Gen. Delivered 4/14/2019.

  7. #7
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    Quote Originally Posted by NAZ View Post
    I had to relieve some areas around the welds to get a good fit. I used a die grinder and flapper wheel to put a large steep chamfer on the back side of the firewall so the weld didn't interfere, that left the front side with the original size hole and tight fit around the tubing.

    Also, I used 10-32 screws (1/4" is rather large) as the fine thread gives me more thread engagement than a course thread. 1/4" fasteners in any thread pitch will have very little thread engagement.
    what length of screw do you recommend?

    do you tap the firewall and frame or frame only?

  8. #8
    Senior Member FF33rod's Avatar
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    just frame. I think I went with 3/4 long 10-32, maybe 5/8

    Steve
    Gen 1 '33 Hot Rod #1104
    347 with Holley Sniper & Hyperspark, TKO600, hydraulic clutch, IRS, Foose 18" Wheels, 245 & 315 BF Goodrich G-Force Rival S tires, DRL, power windows, roadster & hard top, Digital Guard Dog Ignition

  9. #9
    Seasoned Citizen NAZ's Avatar
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    10-32 x 5/8 should be plenty long enough. If you use SS screws be sure you lube them (never seize is best but at least use some light oil) or use cad plated steel button heads and you won't have to worry about thread galling. Also, you don't need to tighten them more than just snug, remember there is not much thread engagement with .120" wall tubing.

    Do not tap the aluminum use a #7 drill for plenty of clearance in the aluminum.

    Here's a tip: first layout your screw holes in the aluminum and double check where the holes will land in the square tubing. Once satisfied with the layout, center punch and drill a small pilot hole ~.070". Then drill 1/8" and de-burr the holes.

    Clamp the firewall to the square tubing aligned (you did use alignment marks right?) and use an 1/8" drill to transfer the top center hole to the tubing. Install a cleco here and continue transferring 1/8" holes to the tubing and cleco working from the middle out. Once you have all the holes transferred you can remove the aluminum and enlarge the 1/8" holes to #7 and de-burr both sides. Then you can enlarge the 1/8" holes in the tubing to #21 tap drill and tap them 10-32.

    Yes, more work than most will do but your holes will be more precisely aligned with less chance your screws won't fit. Short cut this and you will likely see tolerance stack up and fight misaligned screws. Precision up front reduces rework on the back end.
    33 Hot Rod Super Pro Drag Racer
    33 HR NHRA Cert Roll Cage Build

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    Quote Originally Posted by NAZ View Post
    10-32 x 5/8 should be plenty long enough. If you use SS screws be sure you lube them (never seize is best but at least use some light oil) or use cad plated steel button heads and you won't have to worry about thread galling. Also, you don't need to tighten them more than just snug, remember there is not much thread engagement with .120" wall tubing.

    Do not tap the aluminum use a #7 drill for plenty of clearance in the aluminum.

    Here's a tip: first layout your screw holes in the aluminum and double check where the holes will land in the square tubing. Once satisfied with the layout, center punch and drill a small pilot hole ~.070". Then drill 1/8" and de-burr the holes.

    Clamp the firewall to the square tubing aligned (you did use alignment marks right?) and use an 1/8" drill to transfer the top center hole to the tubing. Install a cleco here and continue transferring 1/8" holes to the tubing and cleco working from the middle out. Once you have all the holes transferred you can remove the aluminum and enlarge the 1/8" holes to #7 and de-burr both sides. Then you can enlarge the 1/8" holes in the tubing to #21 tap drill and tap them 10-32.

    Yes, more work than most will do but your holes will be more precisely aligned with less chance your screws won't fit. Short cut this and you will likely see tolerance stack up and fight misaligned screws. Precision up front reduces rework on the back end.

    NAZ, can I just come live with you and build cars with you? I don't know if I've ever had a differing opinion than you - heck I think I might agree with you more than I do with my wife!
    Last edited by TxMike64; 07-10-2019 at 09:48 AM.
    -- Mike --
    TxMike64
    TxM Garage

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  13. #11
    Seasoned Citizen NAZ's Avatar
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    Thought I'd add another tip here. When using rivnuts for the body use the type made for plastics such as these: https://www.rivetsonline.com/steel-c...5/rn1032175pnb

    For the firewall to body mounting I used this style rivnut with backer washers which makes pulling these out very difficult. If you click the link to my build and go to the last photo (fist photo is shown as last) you'll see what it looks like.
    33 Hot Rod Super Pro Drag Racer
    33 HR NHRA Cert Roll Cage Build

  14. #12
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    Quote Originally Posted by NAZ View Post
    10-32 x 5/8 should be plenty long enough. If you use SS screws be sure you lube them (never seize is best but at least use some light oil) or use cad plated steel button heads and you won't have to worry about thread galling. Also, you don't need to tighten them more than just snug, remember there is not much thread engagement with .120" wall tubing.

    Do not tap the aluminum use a #7 drill for plenty of clearance in the aluminum.

    Here's a tip: first layout your screw holes in the aluminum and double check where the holes will land in the square tubing. Once satisfied with the layout, center punch and drill a small pilot hole ~.070". Then drill 1/8" and de-burr the holes.

    Clamp the firewall to the square tubing aligned (you did use alignment marks right?) and use an 1/8" drill to transfer the top center hole to the tubing. Install a cleco here and continue transferring 1/8" holes to the tubing and cleco working from the middle out. Once you have all the holes transferred you can remove the aluminum and enlarge the 1/8" holes to #7 and de-burr both sides. Then you can enlarge the 1/8" holes in the tubing to #21 tap drill and tap them 10-32.

    Yes, more work than most will do but your holes will be more precisely aligned with less chance your screws won't fit. Short cut this and you will likely see tolerance stack up and fight misaligned screws. Precision up front reduces rework on the back end.
    Thanks for the advice. I installed the firewall with #10-24 x 1/2"L screws and it worked well. I broke a tap in the frame and had to drill it out to 1/4"-20 and it worked fine.

    The next issue i ran into was the steering joint flange hitting the frame.

    The two options I could come up with are clearance the foot box to shift the flange towards the drivers side, or notch/clearance the frame. My preference was to clearance the foot box rather than touch a nice powder coated frame. What are your thoughts?
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  15. #13
    Seasoned Citizen NAZ's Avatar
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    Looking at the photos, looks like there is enough room to nudge it away from the tubing if it contacts the tubing -- or perhaps you may need to enlarge or elongate the two mounting holes to accomplish this. Or a spacer between the bearing shell and firewall.
    33 Hot Rod Super Pro Drag Racer
    33 HR NHRA Cert Roll Cage Build

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