Lol well thats no good. Id hate to blow a front brake line on an RX7. Well its not like that ever happens anyway, 9/10 its the lines going to the back that rot.

the order isn't super important, i do the rear first because it has more likelihood of getting air back into the system and having to start over, the rears taking the longest to bleed properly.

my favorite is the left front, because its the shortest...

I'm having similar issues with my brakes.

Bought a shell; brakes were shit. Guy said it was cause he replaced something.
I bought different rear calipers + put those one.
Bought a new (reman?) MC cause old one was leaking.
Power bled with a motive power bleeder + custom cap.
Brakes still feel like sloppy shit. I probably will have to get another reman MC

But my booster does have a good amount of rust on it. I'm wondering if it leaks?

If you have no clear leaks on your calipers, more than likely they are OK. I changed mc's twice and put new front calipers on and still had crap for brake pressure. I will give you same advice as clokker gave me.
Get a matching booster and mc. I was in denial my booster was bad but as soon as I replaced the booster it bled super easy and my brakes worked.

What year Subaru did you get the MC/Booster from. My 86 Base brakes work, but could be alot better. Always thought there was a lot of pedal travel. Just thought it was normal for the single pot brakes.

Nothing to do with the calipers, everything to do with master cylinder size.

There are lots of subaru in the salvage yards around here. Infact way to many on the roads as well

Early 90's Subaru legacy. It has a cylinder shaped reservoir and aluminum 1 1/16"(iirc) mc. The size is on the mc somewhere.

Your pics in post #68 show the stamping indicating cylinder size.

How's the MC/Booster swap working these days? Did the mounting bolts line up on the firewall? Are you able to use the FC proportioning valve? I'm going to the salvage yard this weekend and there are no FCs around here

My swap(s) all work well.
The Honda, Nissan and Subie swaps I detailed all bolt in, no firewall modification required.
Yes, you can use the stock prop valve.

A few suggestions:

1) Brake pads. What brand/Age/Wear
- Some pads use softer material than others. This leads to a soft feel. If they are worn unevenly same thing.

2) Brake pad shims. Do you still have the stainless steel and rubber shims?
-Sometimes the rubber shims rust creating a soft feel. Try pulling everything off so it's just the back plate

3) Does it ever feel firm? If you pump it 3 times and hit it does it feel good?
-This could indicate the pistons are "rolling back" a little too far
-During cornering, especially with opposed piston calipers, the rotors will deflect and push the pistons back into the bore. Next time you hit it, it's soft and comes back when you hit again. Sometimes race car drivers experience this and have to double pump before coming into corners to make sure brakes are there.

4) On the rear calipers I found my had a two bleeders on each caliper.

5) Rear caliper piston adjusters may not be working. Try pulling up on the hand brake a little at a time and see how it feels at the pedal. You will get some change, but this will give you an idea if the softness is in the front or rear. In my old truck with rear drums, if the rear was off just a little bit the pedal was total crap.

additionally all of the Mazdas use the same pattern too, except that the FC uses really long studs to mount the booster, and all of the other mazdas have shorter ones.

Clokker, could you post up a link to one of your swaps? I've tried searching, but you have alot of posts.

Thanks cbrock, I'll run through your check list when I get the back on the road.

^
Wrong subject.
This is about brakes...

i had just finished deleting my abs a few months ago. while i had things apart i figured may as well rebuild all calipers. got it all done and back together, bled it thoroughly, pedal felt like ass. drove it for a bit like this, and noticed after a few weeks it firmed up to the point that it feels good and solid. i have noticed this with other cars i've done brake work on as well. bled it. bled it again. and again. same results. drive for couple weeks, pedal feels great again. unfortunately i don't have a reasonable explanation for this. i just know it's been the case for several of my cars.

Air in the system working it's way to the MC and escaping via the reservoir.
That would explain the time delay.