Shutoff on brake master cylinder

[Davidm37]

I have a 1953 M-37. On the lid that is bolted to the top of the master cylinder there is a shutoff valve on the line. What is this line for and what is the shutoff for. I have the mc out to put a rebuild kit in. Just acquired this truck, rebuilt the brake cylinders and installed new shoes. The brakes weren't working when I got this truck. Thanks

[Matthew Welcher PWA]

That is a shut off vent valve for deep water fording.
You dont need to have it on there and as you normally keep the valve closed.
from the master cylinder the line snakes forward and connects to a fitting up on the air cleaner neck.
Hope this helps.

[Davidm37]

I might just screw a plug in it. The engine has been changed to a valve in head straight 6 cylinder. Thanks for the info.