I'm in the process of upgrading the brakes on our 1979 RX7, which we race in 24 Hours of LeMons.

We've already replaced the rear axle with an early GSL rear with disc brakes. Since that time the brakes have always had a soft/spongy pedal feel. The car stops, but hard to modulate well.

Now we're replacing the front calipers; replacing the '79 wedgies, with 81-83 calipers. I also ordered a new brake master cylinder, but discovered the hose connections are different. The 1979 has what I believe is proportioning valve next to the master cylinder; the brakes lines feed through this valve between the master and the 4 corners of the car.

Is there an alternative proportioning valve I need to get? Or does the newer master cylinder I've purchased feed directly to the brakes; 1 line each to the fronts, and a single line to the rears which split at the axle. If an alternative proportioning valve is needed, do you know where I can purchase one?

Thanks!

 

83 should hook up the same. The opening on the bottom of the master cylinder goes directly to the left front caliper. The opening on the right side of the master toward the front of the car connects to the proportioning valve at the bottom opening marked "F". The opening on the rear right of the master connects to the proportioning valve at the bottom opening marked with an arrow pointing up. The front right hard line connects to the p valve at the top opening marked "F". The hardline from the rear connects the p valve at the top opening marked with the arrow pointing up. The proportioning valves were different part nos. for different years, but I think you will be fine with the 79. I think the threads are different. I think the 79 and 80 models have course threads while the latter models have a fine thread on the brake lines. Parts diagram picture is identical for both years, but the parts nos. are different. Here's the 79 diagram.

 

^ Thanks for the reply.

However, I think I need a different proportioning valve because the original setup on the '79 was rear drums, whose brake wheel cylinders have different hydraulic characteristics than the caliper of the disc brakes on the car now. I believe the calipers need to move more fluid.

Also, the replacement '83 brake MC has an outlet on side in the middle, which interferes with the current placement of the proportioning valve. I don't mind relocating the prop valve. But between the rear brake type differences, and the different plumbing layout of the MC, I was wondering if the proportioning valve changed and/or moved? Or did they do away with it altogether by '83.

Do you have access to a similar diagram for '81 to '83? I believe they're all the same.

 

I found the online links to repair manuals. Diagrams appear the same through 1984. However, the parts numbers seem to change for the proportioning valve. But none of the diagrams seem to illustrate how the plumbing connects to the MC 2 times on the right side, and 1 underneath. I purchased the MC from RockAuto. Any thoughts or experience? I'm in the process of registering with MazdaSpeed, so may be able to get some clarification there.

 

83 diagram is identical to 79 (see below). The part numbers are different for different years and models (drum or disc). Master cylinders vary with year and model also. That said I and others have swapped drum to disc rear end without changing either proportioning valve or master cylinder. I've not done the conversion from SA to FB so I can't say it will work the same as FB to FB.

According to my Mazda parts diagrams here are the parts numbers for the different years and models.

79 P. valve 3591-43-900
Master 8871-43-400A


80 P. valve 8341-43-900
Master 8980-43-400

81-82
S & GS Models
P. valve FA07-43-900
Master FA07-43-400

GSL Model
P. valve FA07-43-900
Master FA18-43-400

83
S & GS Models
P. valve FA07-43-900
Master FA07-43-400

GSL Model
P. valve FA48-43-900
Master FA18-43-400

84-85
S & GS Models
P. valve FA07-43-900
Master FA07-43-400

GSL & GSLSE Models
P. valve FA66-43-900
Master FA66-43-400