laundryhamperman

iTrader: (3)

I haven't seen a really good set of pictures or writeup on this and figured I'd share with part numbers. I ordered an FD brake booster from ebay for $80 which came with the FD master cylinder. Then ordered a brand new Centric brand Mazda 929 master cylinder, Centric part number 130.45604 which cost me $111.17 with tax and shipping. Point of this for those who don't know is the master cylinder from a 929 is larger than an FD RX7, which itself is larger in diameter than the FB. This will give you firmer brake pedal feels as you push more fluid in the larger cylinder than with the smaller. I've got Tii brakes on my car, so I wanted a master cylinder to match, plus I like a firm pedal and opted to upgrade further, going from the FD to the 929. I've read that the FC turbo or any FC large brake cars have a larger diameter brake booster which hits the FB clutch cylinder. The FD I learned is the same diameter as the FB, but it seems to have a double set of diaphragms. Somebody who knows better can correct me on that. Anyway, I got pics showing the booster bolts right up to my 1984 RX7, the 929 master bolts right into the FD booster, and it all fits happy in the engine bay, at least when there is no motor, but it looks like it won't be any problem. There is plenty of space next to the clutch master cylinder which was my primary concern. Anyway here are the pics of what works, enjoy!



FB booster on the left, FD booster on the right.







FB master cylinder on left, FD MC on the right.





929 MC on the left, FD MC on the right.





929 MC in the FD booster





Assembly fits in the FB chassis just fine, plenty of room. FYI I did use the spacer behind the FD booster, and added the spacer from behind the FB booster to double the spacer thickness between the booster and the firewall, this made the brake pedal adjuster land in a sweet spot for adjustment.

KansasCityREPU

iTrader: (9)

The page source shows that the images are hosted on a google account that requires a login. Can you post them directly to this forum?

https://lh3.googleusercontent.com/a8...4=w875-h657-no

spedy7

Yeah, can't see them either. Very interested as my master cylinder shows signs of possible leakage.

t_g_farrell

iTrader: (1)

Maybe you need to make your pics public on that google account. We can't see em.

laundryhamperman

iTrader: (3)

Images are now on a shared album, let me know if they still are viewable. I hosted on google because they are decently sized pictures and I had problems uploading to RX7club.com, possibly becuase they were too big.

j_tso

iTrader: (2)

Yep, they are viewable on my end.

Thanks for sharing this set up. I'm also going to be running a 4-piston set up soon and this was helpful.

KansasCityREPU

iTrader: (9)

Nice work.

sa7

iTrader: (13)

j_tso

iTrader: (2)

welp, looks like FD brake boosters are a bit hard to find. There are a couple of rusty ones on eBay, and one of which is completely the wrong part.
Looks like for now I'm sticking with my plan of GSL-SE master cylinder (same bore size as FC).

sa7, what are you currently using for the master cylinder and booster?

j9fd3s

iTrader: (3)

the bolt pattern on the firewall seems to be some kind of standard, so every booster after about 1977 will bolt up, no need to stick to FD stuff, or even Mazda.

Subaru has some big master cylinders

KansasCityREPU

iTrader: (9)

I know the second gen booster will work, but the holes need to be reamed out for fitment.

j_tso

iTrader: (2)

Is the bolt pattern slightly bigger or just the studs are larger?

Yep, after I posted that I did some poking around on rockauto and found a 90s Impreza has similar size booster for the FB but with a dual diaphragm. That particular Impreza also had a 1" MC so the 929 one should work as well.

KansasCityREPU

iTrader: (9)

I'm not sure. trochoid's old widebody had second gen brakes (RE-Speed) so he also replaced the booster with a second gen. I think one of the reasons is because it hit the clutch master.

miasmicmonky

iTrader: (1)

Do you still need a separate proportioning valve to make this work?

sa7

iTrader: (13)

laundryhamperman

iTrader: (3)

Is the SA chassis using a smaller booster and the clutch cylinder is closer? I can get a measurement of the booster diameter on Sunday evening for you.

And for the prop valve question, you should have the prop valve that is appropriate for your brake rotor and caliper setup.

j9fd3s

iTrader: (3)

https://www.rx7club.com/2nd-generati...t-deux-852021/

sa7

iTrader: (13)

sa7

iTrader: (13)

HotGritz910

I know this is a old tread but how did you guys adapt the fb rx7 3 brakes lines to the 2 port master? Im having a hard finding fittings that will work.

j9fd3s

iTrader: (3)

Mazda used to have a Y fitting, EA03-45-451B, although a T fitting would work too. in an ABS car the master just has the 2 ports, front and rear, and then the ABS splits the fronts, to make the 3 channel system. in a Non ABS car, the master has three ports, rear, and two for the front.

if you're in the junk yard a 1990-2005 Honda might be good, they have a ton of brake lines on the firewall, i think it has something to do with the way they did the LHD/RHD on those. failing that a 3 channel ABS car will have a splitter in the back somewhere, FC, miata, etc

elwood

iTrader: (1)

I installed a 1" bore MC in my FB with the original booster and T2 front brake. It transformed the pedal feel (for the better). If you use pads with at least a medium coefficient of friction, you won't need a dual diaphragm booster. There's nothing wrong with the OP's strategy, but you can avoid swapping the booster if you use the Nissan Patrol 1" bore MC or an aftermarket equivalent. Either way, you'll be dealing with brake lines and prop valves to get it tuned properly. Read this thread from a couple of years ago:

https://www.rx7club.com/1st-generati...inder-1129142/

tommyeflight89

iTrader: (4)

Figured I would ask in this thread... what is the best tool/trick to removing the last brake booster nut?

Crawling under dash and removing the first three was pretty easy, but the last one seems to be right beside a sheet metal reinforcement bracket.

A crows foot maybe? I didn't spend much time yet wrestling with it, figured someone might have a good trick!