I could swear that somebody posted a generic brake line part number to do the simple front/rear split dual MC upgrade(not the diagonal setup), but I've been searching every possible combination to find it.

I think you use the existing line to the single MC for one circuit (does it matter if it's the front or rear brakes?), and add an line to run the other circuit.

I would love to find the thread that has the part number to figure out why I couldn't find it through the search function.

Thanks-

Paul

Paul,

Here is so mine is configured. I'm using the early 80's dual-circuit master cylinder.

The rear line has been disconnected from the OEM junction block on the firewall. A short generic parts store line runs from the master cylinder port to the existing long rear brake line. The short generic line and long OEM line are connected with a female/female union fitting. Both the short line and union came from the parts store.

The front port on the master cylinder goes to the OEM firewall junction block, where it splits off to each front wheels just like before. I used a plug to block off the open port on the junction block (where the rear line lived before). The plug came from the parts store as well.

You'll find most stores have quite a selection of brake lines and fittings. Sometimes it easier to ask if you can look back there yourself.

Any idea on the length of the short one? I thought I remembered the post I saw said it was 18"?

Paul

My short lines are not actually over the counter items. I fibbed a bit for the sake of simplifying the explanation, not knowing what master cylinder you plan to use.

I made the lines up myself because it required "normal" 3/8"-24 threads on one end for the junction block, and metric threads on the other for the Mazda master cylinder fittings. I had already invested in the line and fancy flare tool for other projects.

Don't know the lengths, but here are some pictures. Ignore the wiring mess, it will be tidied when the new engine goes in.



Union fitting between fender well and steering shaft.




Junction fitting. I think the rear line normally runs into the bottom.

That's neat. What specific Mazda MC did you use? Any comments on how the braking ability and front rear balance is compared to the original?

I'm RHD so the pipes come out the "wrong" side but that's not a deal breaker but plumbing in a servo not so easy unless you want it to only assist the front brakes. New cast iron Volvo jam pots are about $160 here in the UK.

It's from a mid-80's RX7 that originally came with rear drums just like Volvo. I believe the bore size is also a very close match for the 122. Mine came with the reservoir and low fluid switch. The mounting pattern is very very close to the Volvo, just needed to enlarge the holes a bit. I think I paid $30 something dollars for mine from Rockauto.com. The part number on the invoice is 0728107.

I'm not sure of a part number, but I would unhook the rear brake line from the 4-way union (actually, I guess it's a 5-way with the brake switch...), and get a short length of pre-formed line from Napa or a similar supplier. Then get a 3/16" brake line union and a cap, to connect the lines and close off the extra port on the 4-way union.

If it were me, I'd run all new brake lines instead of adding the union to the rears. It would bring the cost to maybe $30 instead of $10 (not counting a master cylinder or rubber brake hoses).

Ben