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

roger1

roger1

Master Mechanic
Aug 23, 2010
383
63
San Angelo, TX
Would this be Overkill for a stock set-up?
Not trying to de-rail the OP. Just curious for informations sake?
Stock setup is 15/16" bore. '81 and up is a step-bore 15/16". The short larger bore (I think about 1 1/4") is to take up the slack in the low-drag metric calipers before they apply pressure to the rotors using the smaller bore.
 
Tomeal

Tomeal

Greasemonkey
Apr 17, 2016
140
43
Clyde,pa
Stock setup is 15/16" bore. '81 and up is a step-bore 15/16". The short larger bore (I think about 1 1/4") is to take up the slack in the low-drag metric calipers before they apply pressure to the rotors using the smaller bore.

So would the foot feel a difference?
 
nomoar

nomoar

n00b
Aug 27, 2014
4
1
Has anybody used the ACDelco 18M974 with the 12" dual diaphragm booster (b-body booster upgrade)?
 
64nailhead

64nailhead

G-Body Guru
Dec 1, 2014
916
93
Upstate NY
78-80 uses a different master than 81- and up
^^This is what is needed to be known to determine master cylinder choice IMO. If I would've known this at the beginning of the upgrade, then I would've struggled much less.

Has anybody used the ACDelco 18M974 with the 12" dual diaphragm booster (b-body booster upgrade)?
If you know what booster you have, then you figure out which master cylinder will work.



I want to pass it along that I don't believe that I can get better braking than what we have with stock components - the Riv master works great with the disc upgrades we installed. This thing will stop like a new, modern car presently. After putting the C5 fronts I thought it was night and day, but after the rear disc and master cylinder upgrade it is waaaay better. I would recommend the Riviera master to anyone that has an '80 and earlier booster.
 
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