I am going to be installing a shut-off valve on the carburator and I have a question about the copper gas line going to the firewall (see pic).
The fitting on the firewall, is that set up so the gas line can slide thru the firewall or does this part of the gas line go from the firewall to the carb?
It should not go through the firewall at all. You need to replace it. It should run along the frame.
The only 'fitting' that is on the gas line running from the sediment bulb to the carb is a clamp to secure the steel (or brass) gas line from wiggling.
The gas line is free floating and should not touch the firewall.
That clamp is on the nut and bolt that hold the controller arm to the frame.
Best to use steel brake line, not copper tubing.
The original Ford gas lines were tin plated brass.
The firewall has nothing to do with it.
You didn't say what the vehicle is, but I'm assuming it's the TT in your profile.
I dislike carburetor shutoff valves because the ones sold for the purpose are so stiff I have to use a wrench to work them, and the ones that look period correct are high-priced. So when I saw this setup on a TT I did the same thing on my 1915 runabout.
It's easy to reach the handle from the side of the vehicle and the connection at the carburetor remains perfectly stock.
Here's my version.
The handle is under the running board.
The little piece of pipe that fits over the valve handle pivots on the shaft to accommodate the change of angle when it turns. I intend to add this convenience on all my T's.
I agree with Jeff on the steel line even though it's not strictly correct. It's much less susceptible to metal fatigue.
I just replaced my shut-off with one I like better that the more modern looking one I had. I always use steel brake line since a copper one failed on the racer in the 70's.
This valve has some packing and probably wasn't intended for gasoline. We will see how well it works.
The tube union let's me try different arrangements more easily.
Fuel Lube makes the valves work smoothly but only for a few months.