I have large 4-piston calipers, and I'm getting some pad knockback. One way to mask the problem is using a master cylinder with a larger bore. The FC non ABS / non AAS MC has a bore that is 22.22mm vs. the '84 FB's 20.64mm bore.

Has anybody made this swap?

Since the bolt pattern on the MC mounting flange is clocked 90deg, did you use the FC booster?

Clearance to the clutch MC?

 

Trochoid did this swap on his widebody. Not sure if he did a write-up. He hasn't been on the forum in a long time. I think I remember him saying the bolt holes where close but had to do some drilling. I've seen it and it was a close fit. He has the Re-Speed big brake conversion with Mosser axels.

 

What is pad knockback?

 

StopTech has a pretty good explanation here: Pad Knockback

 

Thanks. I couldn't find a thread on the install, but I did find the For Sale thread for his car . . . and it mentioned the FC booster and MC. That answers most of my questions.

 

From what Ive heard the base model FC booster, and turbo master cylinder is a perfect fit.

Considered that swap myself, but my FB master is working fine at the moment.

 

I installed the FC master on my SA booster. Used the two side bolts and elongated the holes in the master cylinder slightly to fit the wider pattern. The side bolts were almost too short when used with the stock spacer, but they did fit (barely). The SA booster had 4 bolts, chopped off the top and bottom bolts. Worked fine except that the SA used different threads on the brake lines and the lines had to be modified to fit. I couldn't use the FC booster because it would have hit the clutch master cylinder.

Build02 | Flickr - Photo Sharing! Build02 | Flickr - Photo Sharing! by GySgtFrank, on Flickr

The '93 Ford Cobra MC I've gone to is an even better fit on the SA booster. I was able to ditch the stock spacer and bolt it directly, with the same hole elongation that I had to do on the FC master. It has a 1 inch (25.4mm) bore. The SA booster and the Cobra MC are both Bendix brand parts and fit almost perfectly. I used the Ford proportioning valve and plumbed in a rear brake pressure adjuster.

Cobra brake master cylinder 2 | Flickr - Photo Sharing! Cobra brake master cylinder 2 | Flickr - Photo Sharing! by GySgtFrank, on Flickr

Hope that helps.

 

Although it pains me immeasurably, I have to express gratitude to a Marine (I was USAF).

It looks like this is the booster attachment scheme:
SA 4 studs -- 2 vertical, 2 horizontal
FB 2 studs -- vertical
FC 2 studs -- horizontal

If I want to go to a larger bore MC, both viable options (FC and Cobra) have 2 stud horizontal mounting, so I'm left with the following options, as I see it:

1. Rotate my booster 90deg (Even if this is possible, it will put the vacuum port in a weird location. Maybe I could clock the forward shell of the booster or relocate the port?)

2. Move to an SA or FC booster

3. Search for a different MC with vertical attachment to match my current booster.

4. Bore my current MC to 1" and find new internals to match (least attractive of the options).


A few questions regarding the Cobra MC swap:

A. Does the Cobra MC seal against the SA booster correctly?
B. Did you consider ditching the OEM prop valve and just use the aftermarket adjustable one for rear brake proportioning?
C. Why did you make the change?
D. What are your impressions of the new setup?

 

the brake booster to body bolt pattern is generic to every Mazda from like 1977-now, which means you can use any booster/master combo you want.

even better is that Honda appears to have the same pattern too.

so pick the master you want, and use that booster and its all a bolt in

 

A. The Ford MC seals up against the booster perfectly.

B. I used the Ford Racing adjuster (shown in the pic) for rear brake proportioning.

C. I had a brand new Fox body Mustang to SN95 Cobra conversion kit sitting on the shelf that was not going to be used. The kit was for a complete conversion from the rear discs to the front 13" discs. I wanted to use as much of the complete kit as possible as it had all been engineered to work together. The only thing I haven't been able to use so far is the booster.

D. I only have the MC and rear brakes done at this time, with the stock SA front discs still in place. It is a HUGE improvement even so. Much better brake feel and increased stopping power over the Stock SA setup, which truly Sucked ***.

Bendix has beaucoup MCs on their site, I would be surprised if they couldn't match up exactly what you are looking for. Also, as J9FD3S said, there are others as well. I've heard the 929 MC (also a 1" bore) is almost a direct bolt on. I've never actually done it though, so have no valid experience to share on that swap. I posted mine because I have actually done it and it works well, both the FC and the Ford MCs will work with some modifications on the SA booster.

 

I've decided to try residual pressure valves first. I plan to install one 2 lb valve at each corner after reading the experiences of a few car builders. If anybody has any experience with this, please share.

 

I did a partial write-up of a 1993 929 Non-ABS BMC, 2003 Protege PBB, and Wilwood Prop Valve if you search my threads.

The capacity noticably more than stock, and pricing was $200 for everything.

 

Nice writeup.

- The '03 Protege Booster looks thicker than the OEM FB one, which may cause a packaging issue in my car. Is it a tandem unit?

- The 929 MC is interesting to me because the front brake circuit is at the front, and the rear is at the rear. The FB (and most older setups) had this reversed. If you look at the way a dual piston MC works, it seems to me that the old way would be better.

- What are your impressions of the setup?

 

I contacted The Brake Man today, and they make residual pressure valves that will screw right into the 10mm X 1.0 Inverted Flares on our master cylinders. I ordered a pair of the 2PSI RPVs -- one for each front line.

Another nice feature is that the internal spring can be changed to a higher PSI rating, if necessary, without replacing the whole RPV.

 

The Protege and FB brake boosters are identical in size. Sorry to say it, but I've been away from the car for months now and really haven't been able to start it since ownership. Once it runs I'll update the rest of my writeup.

PS. I hate flaring brake lines with a passion. Using 3/8" fittings on 6mm lines is a bit of a bitch to seal too. I honestly think I'm missing the fittings at the end of the BMC. I bet that's where my leak is.

 

As an update, I installed 3 X 2lb residual pressure valves:
- One on the underside of the master cylinder in the brake line to the left front caliper
- One on the top side of the prop valve in the brake line to the right front caliper
- One on the top side of the prop valve in the brake line to the rear calipers

I think the problem is solved. After some aggressive hard turns on the street, the brake pedal is still firm. I'll need to do a track day to verify, since I suspect the higher G-loads exacerbated the problem, but so far, so good.