Volvo owner wants to try 1stgen RX-7 master cylinder brake swap...
 

Howdy folks. I don't own an RX7, unfortunately. My project car is a 1967 Volvo 122s. Cool little cruise around town car.

http://lh6.ggpht.com/_8ipvB_cNrbc/Sn...0/100_3316.JPG

Now, for my RX7 related question. The Volvo was originally equipped with single circuit brakes (front discs, rear drums). I'm in the process of upgrading to dual circuits for the improved safety and peace of mind. I had heard, without much confirmation, that using a 1st generation RX7 master cylinder from a rear-drum car was a much cheaper alternative to the $150 or so the dual circuit Volvo unit that appeared in 1968 runs.

Rock Auto was having a closeout on the Disc/Drum RX7 MC for $28 including the low fluid switch and reservoir, so I figured I'd give it a shot. I had to overbore the mounting holes slightly and shorten one of the bolts, but it bolts up pretty nicely with those small changes made.

http://lh3.ggpht.com/_8ipvB_cNrbc/S6...2/100_4060.JPG
http://lh5.ggpht.com/_8ipvB_cNrbc/S6...2/100_4061.JPG

Now for the questions.:
- Which ports are which (front/rear)?
- What is the port on the bottom side for?
- What size threads are the fittings?

Thanks for any information you guys might be able to contribute!

neat car!

the rear line is the one labeled R, in the front with the little valve on it

on the Rx7, its like a 3 circuit car, it has the rear line, and then two lines for the front. in the stock configuration the left front goes right to the wheel, and the right front and rear go to a proprotioning valve.

i think you'd be ok if you blocked a port off, and just did front and rear, thats essentially what mazda did later, with ABS, i'm not sure how the volveezy is plumbed.

the threads are 6x1.0

Thanks for the reply. Everything you described makes sense. I may block off the lower port for the front lines, or just run one front wheel from each port instead of tee'ing it off farther down the line.

M6x1.0 sounds pretty tiny. M10x1.0 is a lot more common on brake setups. . . any chance that's it?

lol, maybe 10x1.0 is right... lol, yes it is 10x1.0...

yeah i'm not sure how your car is plumbed, and mazda essentially did it both ways

question for you! in the second pic that silver round thing behind the master, is that the flasher?

It's a relay, not sure which one to tell the truth. The car is dirt simple electrically, only 4 fuses total, so it's probably something related to the lighting.

The Volvo uses a single line going from the MC to the fender-mounted booster, a single line from the booster to a 3-outlet distribution block. 1 outlet goes to each front disk, the remaining outlet heads to the back of the car for the rear drums.

Plan right now is to run the front outlet on the RX7 MC to the booster, and then to the OEM distribution block. The rear brake line will be removed from the OEM distribution block, are have a section of tube made up to connect it to the rear outlet on the MC.

Cool Volvo, I'm taking ownership of a 142E here pretty soon (MY71),
tell me how your upgrade goes, I might follow suit.

Dual-circuit brakes started making appearances on Volvos in 1968 on the 122 and 1800 models. Some early builds in that time frame have the dual-circuit master cylinder but the single-circuit pipework. I'd wager that buy 1971 most models were running dual circuit brakes.

Interested to Sell?
 

Hello.
I came across your photo and just absolutely love your car. I don't know how you would feel about it, but I would be interested in making an offer for the Volvo. Please let me know if you would be interested. Thank you.