Master cylinder for Blazer brake upgrade with C5 fronts and (stock drum rears) 12/18-upgrade to rear disc

8

81cutlass

Royal Smart Person
Feb 16, 2009
1,451
1,786
113
Western MN
#22
From doing some more reading, and looking at pictures on Rock Auto, it appears that later models might have an option for a larger bore booster to accept the mater cylinder I bought. We have the double diaphragm booster that appears to be the stock '80 Cutlass 'HD' unit. But it does not interchange, according to Rock Auto with much of anything newer than an '81.

81cutlass, what year is your car that you put the larger m/c onto?

Does anyone else have a booster laying around that could be measured?

Lastly, we were thinking of swapping to the single diaphragm booster for appearance only. Is the stopping power, required foot/leg pressure varied from the double diaphragm?
I put it on an 86 grand Prix v8 car. I got the mc from a salave yard off a 89 Caprice I thought. I looked back at car-part.com and they don't note any difference in big vs. Small mc on b bodies. Rock-auto does seem to have 2 different fitment sizes. Maybe I got a small b body one? Regardless it still helped
 
64nailhead

64nailhead

G-Body Guru
Dec 1, 2014
824
900
93
Upstate NY
#23
I've had both & never noticed a difference.
That's what I'm looking for - thank you.

Also, I drove the car yesterday in an attempt to tune the traction control with the local dyno operator running the laptop, implying there's about 5000 miles less rear tire today than yesterday. And the stock master works fabulously other than the pedal is a little deep. It really has me rethinking the entire swap because the car stops so well. I'm going to check out a newer booster locally and see of it will accept the larger master.
 
TURNA

TURNA

Geezer
Jul 24, 2009
6,305
7,966
113
Socialist NY
#25
Disk/drum
 
1

1KWIKSIX

Apprentice
Jun 26, 2017
94
139
33
#26
That's what I'm looking for - thank you.

Also, I drove the car yesterday in an attempt to tune the traction control with the local dyno operator running the laptop, implying there's about 5000 miles less rear tire today than yesterday. And the stock master works fabulously other than the pedal is a little deep. It really has me rethinking the entire swap because the car stops so well. I'm going to check out a newer booster locally and see of it will accept the larger master.

Suggest installing 2# residual pressure valve(s) in front brake line(s) & 10# in rear line = much more immediate braking response (less pedal travel to engage the brakes)

residual-pressure-valves-jpg.95556
 
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1

1KWIKSIX

Apprentice
Jun 26, 2017
94
139
33
#27
I"ve got a gently used B Body dual diaphragm brake booster , just taken off car. This is a larger diameter than the G body unit and should offer better braking. $50 + shipping
 
64nailhead

64nailhead

G-Body Guru
Dec 1, 2014
824
900
93
Upstate NY
#28
Done driving for the season - of course. Getting ready to install rear discs. To summarize to this point, the brakes with stock rear drums , booster and m/c will bring this to halt on a dime. Pedal is a little deep, but by a little, I mean nothing that's concerning. The goal is to get it to stop before it's 75% of the way across the dime lol. We have a rear disc kit from Inline Tube that includes rotors that will fit inside 15" rims so that we can throw on the 275/60R15's and be class legal. The kit also includes parking brake cables so that we can pass a state inspection.

The folks at Inline Tube's tech line advised to use a stock F-body master for a disc/disc car from 1982 so that it will have standard fittings do that I don't have metric fitting at the master and an SAE at the proportioning valve. They advised that F-body master will work great for pedal travel and braking force. They also advised I should grab a disc/disc proportioning valve - so I did. The question comes down will the stock '82 F-body master cylinder fit into a stock, single diaphragm '83 or newer booster? Also, how much bigger in a diameter is the single booster than the HD double diaphragm booster?
 
TURNA

TURNA

Geezer
Jul 24, 2009
6,305
7,966
113
Socialist NY
#29
The single is around 11 when the double is about 8
 
roger1

roger1

Master Mechanic
Aug 23, 2010
325
327
43
San Angelo, TX
#30
I went with a dual 11" for a '90 Caprice application. Ended up going with an '80 Riviera 1" master. It was a perfect combination with my LS1 front brakes and stock rear using S10 7/8" cylinders.
Super high and very firm pedal feel. Stock combo valve.
 

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