are there any master cylinder upgrades for our cars?

[G_Body_Enthusiast]

i know some guys on the monte ss site have swapped out their boosters for the larger dual diaphragm booster but what about the master cylinder? are there any OEM type master cylinders that can be used as an upgrade? i'm asking because of the blazer spindle/brake swap and i'm wondering if another master cylinder would help or is even needed. i have the stock dual diaphragm booster and i hate the feeling of my pedal near hitting the floor to stop my car. maybe a b-body master cylinder too? yeah it requires more pedal effort but i've owned a b-body before so i know how the brake pedal feels on them and it always felt better compared to the one in my GP.

if using the two piston caliper exerts more force because of surface area increased over the single piston stock caliper would it require more fluid to do so or no? on this i'm kinda hazy on so i'm really not sure. i dont know what the volume is for either caliper so i cant do the math to find out if the twin piston caliper needs more fluid i suspect the bores are closer to the diameter of the pistons than for the stock caliper giving a similar volume between the two but i have no way of proving this.

anyone care to chime in and help me figure this out?

 

[deanlemans81]

The master on my 81 Lemans stated leaking (pissing is more accurate) from the seal at the back about a month ago. It was still using the original cast iron master cylinder from 81. I replaced it with one from a 87 GransPrix. It is aluminum so it saved a little weight, it was about 2 inches longer overall but the lines plugged right in with a little tweaking. The overall cylinder diameter was about 1/4 to 3/8 inch wider (I didn`t measure it) but it bolted right on. I have not done any math but I can confirm that my brake pedal is much firmer and applies more pressure that it ever did even before the leak. You should give that a try.
Dean

 

[Bonnewagon]

About all you can do is go to a larger bore master. Say you have a 7/8" bore, a 1" will give more volume but at greater pedal effort. But with a power booster, so what? My '81 Malibu had the shitty 7/8" master for that Granny-easy-effort-pedal-to-the-floor braking. I used an '80 Firebird 1" master and wow what a difference. Pedal travel was cut in half, and with the booster, effort increased minutely. Of course if you already have a 1" master, a larger 1.25" master would do the same. Luckily most GM masters interchange easily.

 

[85GPLef41]

I read somewhere that the B body master cylinder was a good upgrade. I haven't gotten that far yet though. :| Bonnewagon your quote on your sig is making me nervous....

 

[cat herder]

About all you can do is go to a larger bore master. Say you have a 7/8" bore, a 1" will give more volume but at greater pedal effort. But with a power booster, so what? My '81 Malibu had the shitty 7/8" master for that Granny-easy-effort-pedal-to-the-floor braking. I used an '80 Firebird 1" master and wow what a difference. Pedal travel was cut in half, and with the booster, effort increased minutely. Of course if you already have a 1" master, a larger 1.25" master would do the same. Luckily most GM masters interchange easily.

Power brake cars all came with 15/16" masters, manual brake cars had 7/8". If you had a 7/8" bolted to a power brake booster, somebody in the past put the wrong part on.

 

[azmalibuwagon]

Hah! I actually did that when I was about 6 years old, and then tried a lamp socket for good measure. If you learn by making mistakes, I must be getting close to being a genius by now.

I put a B body master and booster in my wagon when the original one failed, and it works just like Bonnewagon says. Harder pedal, better stopping power. It's a lot different from the old one; I like it.

 

[G_Body_Enthusiast]

ok some of what you all are saying is confirming what i've been thinking, to go with a b-body booster and master cylinder. i think the b-body master is slight larger in diameter so it would give me the extra volume but with increased pedal effort but trading uop from the 9.5" dual to the 11" dual for a b-body would almost negate the increase pedal effort. as it is now my pedal just seems like i'm putting my foot into a bowl of mashed potatoes every time i hit the brakes. its not air in the lines, it's not faulty parts. i ampractically fanatical about my brakes but i'm sick and tired of working with these underpowered brakes. they're just mushy and not performance oriented at all.

i get they used the cheapest parts that did the bare minimum and designed them so grandma can have an easy time driving to her bridge club meetings but this is just horrible. compared to todays brakes these things are going to get someone hurt/killed or something destroyed. i'm eyeballing some vette brakes for the front but i need better brakes sooner rather than later. i'm willing to wait for other goodies for the car but i dont think i can really wait to save the money up to get vette brakes and drive with this crap on my car in the mean time. and really the blazer brake upgrade is a bolt in and everyone who has done it has been quite happy with it. and i can yank both spindles at the pull a part and pay maybe 70 bucks for the assemblies. too bad i blew my budget this month...gotta wait till august.

thanks for confirming that not i'm not totally crazy, yet.

rockauto is showing for an 85 GP a master cylinder with 24 and 36mm bores. they also show an 89 caprice with 28.6 and 40 mm bores. fittings are the same so it will bolt right in. for an 81 firebird they show the same bores as the caprice, 28.6 and 40 mm. an 80 firebird shows 1" for manual, 1 1/8" for power/rear disc brakes. i think i'll go with the b-body master and booster and the blazer brakes in the front till i can get some money up for the big brakes i'm really wanting. p-s-t has a kit that allows you to use a single bracket and hub to work with 3 different sized rotors from a vette. aside from the kit you buy from them everything else you can get at the local parts store and presto change-o vette brakes. they're 400 bucks and come with aluminum caliper brackets, forged aluminum hubs, hoses, bearings, seals and screw in studs, 1/2"-20 pitch. i may get this kit as i can use 12.8" (2 piston caliper), 13.4" (also 2 piston calipers) or 14" rotors with 6 piston monoblock calipers. the two larger rotors require 18" or larger wheels. at least i can use 12.8" rotors which is quite a stretch from these 10.5" single piston POS granny brakes.

 

[cat herder]

Other cars with the same booster/master combo as yours don't have the same mushy pedal problem you describe. You need to put on your thinking cap and figure out what's wrong instead of throwing parts at it.

9" booster is dual diaphragm, the 11" is single. There's no real difference in pedal feel between them.

 

[G_Body_Enthusiast]

Other cars with the same booster/master combo as yours don't have the same mushy pedal problem you describe. You need to put on your thinking cap and figure out what's wrong instead of throwing parts at it.

9" booster is dual diaphragm, the 11" is single. There's no real difference in pedal feel between them.

compared to the b-body i owned before with it's much better brakes this pedal feels as soft as dog sh*t on a summer day. the brakes are fine, i just think they suck compared to the parisienne's brakes. i know how to work on brakes but thanks for subtly suggesting i dont know my own car. i've owned it 15 years and the brakes work fine.

they're no different than other g-body brakes ive driven. like i said, i just think they're too soft. i like a firm pedal. stock g-bodies do not have a firm pedal in my opinion. so you dont think stock g-bodies have a mushy pedal, good for you. doesnt mean everyone else shares your opinion or if theirs differs from yours they're stupid and dont know how to work on brakes.

they also dont hold up to "spirited" driving. they tend to heat up fast and give you the dreaded brake fade. otherwise they work fine, but i dont drive like grandma going to church. i am using my brakes in a way they were not designed for. so when i say they suck it's for a legitimate reason, not because you think i dont know WTF i'm doing with my own car.

 

[cat herder]

LOL

Good luck finding your 11" dual diaphragm booster.

'Brake fade' is caused by either overheated pad compound, or boiling brake fluid in the calipers, neither of which can be cured with a master/booster swap.

Parisienne... better brakes for 'spirited driving'... oh jesus

...but what the fk do I know, I only have 15 posts or whatever which means I'm probably just a dumb teenager who only bought my first car last week, right?