Firewall

[MBB Larry]

In planning stage. Thinking of going with "Button Heads". Question>> Tap thread into frame, or install rivnuts??
Also, suggestions on sealing between frame and firewall. Was thinking of some kind of strip to apply??

[HVACMAN]

I used 10-32 Button head machine screws. Use a drill/tap, it will save a ton of time.

[CVOBill]

I did the same thing as Andy.

[NAZ]

Drill & tap for 10-32, S.S. button heads. I like the fine thread so I get as many threads as possible in the .120" wall tubing. You don't need nearly as many screws as most folks (including myself) used. But remember to use anti-seize or some sort of lubricant when using S.S. fasteners as they are notorious for galling. There's no reason to use nutserts in .120" wall tubing and the larger diameter hole only diminishes the strength of the tubing with no benefit to the bolted joint.

When joining the body to the firewall I recommend you use nutserts designed for plastics such as these from McMaster-Carr:97217A376 (https://www.mcmaster.com/#97217A376). On mine I used flat washers as a backing to spread the load over a greater area to help strengthen the joint.

As for sealing the firewall to the chassis; I wouldn't /didn't. You have many more large openings to worry about than the seal between the chassis and the firewall. Because I'm building a race car I had to seal some openings around the firewall with aluminum to meet NHRA rules but if that were not a requirement I'd have left these small opening alone.

[MBB Larry]

Great info. I will go that route. Thanks!

[MBB Larry]

Thanks again Naz. I was looking through some old forum posts and saw this>> Had me a little confused about the tubing thickness?? >>


Cut and pasted from the email they sent me when I just asked:

"here are some of the various tubing sizes used on the ’33 chassis (all are mild steel):
o ¾” Square: 0.049” wall thickness
o 1” Square: 0.083” wall thickness
o 1.5” Square: 0.095” wall thickness
o 0.75” Round: 0.125” wall thickness, DOM tube
o 1.5” Round: 0.120” wall thickness, DOM tube"

[JimLev]

I drilled and tapped (10x32), initially used black button heads, but then changed them to stainless phillips screws.
I'm using as few rivets as possible, prefer screws they are easier and quicker to take out.

[NAZ]

Larry, if your source is FFR I'd say that's the correct wall thickness. I've cut most of the chassis apart so at one time I knew the wall thickness of every size tubing but I was going off memory and at my age that's not the most reliable reference. My wife says I can hide my own Easter eggs.

[MBB Larry]

Thanks Naz :>) I will turn 70yrs next year. Oooops, Forgot what I was going to say!!! I am working alone with
my 3-Granddaughters (7/10/11yrs). I am trying to retire, but my company will not let me. I hope to have the year end off to really get started. Just trying to plan out, and configure the machine. Was going Roadster, but live in Texas. Think I will go with Coupe and A/C. SBC 383 with 5-speed.

Thanks for your advise. Where can I see pics of your car?
Larry

[MBB Larry]

Thanks. Just looked at Drill/Tap.

[NAZ]

Larry, if this link doesn't work you can search the album gallery for FFR 33 HR NHRA Roll Cage. My build is way over the top from what most folks are doing. It's a real race car posing as a street car.

https://thefactoryfiveforum.com/album.php?albumid=1042

[MBB Larry]

Wow, You sure did a lot of work! Your right, a race car. Mine is planned on just being a cruising car. I'm sure you have a lot more equipment than I have. Thanks for you help.

[Svtfreak]

I did same as Andy. You’re not doing much serious support so it should be fine drilled and tapped. The finer the thread the better. I wouldn’t support anything that had some weight or some stress on it but for holding aluminum in place, it’ll be just fine