1600 Loadstar Master Cylinder brake lines

[Dougt]

I just bought a 1967 Loadstar 1600, 304V, 2WD, 2 Spd rear axle, T17 Transmission, Power brakes, Oversize rear brakes. Two brake lines are currently piped into the master cylinder on the right side, on a tee. The stop light switch is also mounted on the same tee. The parts catalog shows the stop light switch mounted in the middle, and, I assume, brake lines piped to the left and right ports. I am planning on replacing the master cylinder with a USA-made OEM (Navistar) one, also getting the brake booster rebuilt. Previous owner said he'd rebuilt master cylinder a few years ago; when I bought the truck it had no brakes (no pedal). Also going to replace some rusty looking brake lines and old hoses. But getting back to the master cylinder, why was everything piped to the right? Was it just easier to pipe it that way? The pictures are the existing piping, parts catalog, and the new master cylinder end. Should I re-pipe it? Which line goes on the left? Will it make a difference?

 

[Jonas1ne]

From what you’ve described, it sounds like a previous owner probably replumbed it for convenience rather than for any functional reason. On a single circuit brake system like your ‘67 Loadstar, both outlet ports on the master cylinder feed the same hydraulic chamber internally, so using one port with a tee versus one line from each port generally won’t change braking performance.
Since you’re replacing the master cylinder and brake lines anyway, I’d be inclined to plumb it back to the factory configuration shown in the parts manual. That way the stop light switch and line routing match the original design, and it’ll be easier to service in the future. Just make sure to bench bleed the new master cylinder and thoroughly bleed the entire system once everything is installed.
It would also be worth checking whether the current plumbing was done to work around a damaged port or fitting on the old master cylinder. If both ports on the new OEM cylinder are good, I’d go back to the factory layout.