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

Northernregal

Northernregal

G-Body Guru
Oct 24, 2017
804
93
Red Deer AB
When I spec'd out my brakes I talked to wilwoods tech department a bit and even with the 6 piston fronts and LS Fbody rears they recommend a 1"MC with the 8" dual diaphragm booster. I was looking for a bit more travel for modulating with the pedal.

The LS Fbody rears fit inside my 15" rims. No grinding or modification needed. I installed Turna's MC and it is a bolt in affair. You also don't have any metric bubble flares on your car, mine is an 1987 Regal and not a single bubble flare on the factory lines. Only had to change a couple line ends to 3/8x24 IF to bolt in my wilwood adjustable prop valve. Brake mods on a G are surprisingly simple to accomplish.
 
64nailhead

64nailhead

G-Body Guru
Dec 1, 2014
916
93
Upstate NY
I have the rear disc kit from Inline Tube installed. It has worked well except for the driver side parking brake cable that is too short (they're working on rectifying that I've been told.)

I took it for a short drive/burnout in the driveway with the stock master cylinder and the pedal was veeery deep. Swapped over to an '80 Riviera disc/disc as suggested and it feels great! The pedal is where it was with the stock brakes and master cylinder. Much better than with the stock master with C5 fronts and stock drums (which more than tolerable, but just a little deeper than stock.)

I took pictures of three master cylinder outside bores to illuminate the problem with using a B-body master on the pre'81 stock booster. The Riviera master is .010" in diameter and fits comfortably into the booster, but the F-body master is close to a 1/4" too large in diameter. From looking at photos around the internet it's visible that the '82 and newer have a larger bore booster.
'80 Cutkass stock.JPG
'80 Riviera disc_disc master.JPG
'80 Riviera disc_disc master.JPG
'80 Riviera disc_disc.JPG
'80 Cutkass stock.JPG'80 Riviera disc_disc master.JPG'80 Riviera disc_disc.JPG'90 F-body.JPGIMG_0827.JPGIMG_0829.JPG
 
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TURNA

TURNA

Geezer
Jul 24, 2009
8,257
113
Socialist NY
So is ACDELCO 18M95 the master you wound up using?
 
MTP-Madmat

MTP-Madmat

Apprentice
Feb 27, 2018
82
33
I’m looking to fix/upgrade my brakes on my 78MC. right now the master, booster and prop valve are stock with stock front and 4th gen f body rear. I think the master went bad. Stiff at first then straight to the floor. What master will fit the stock booster that has a bigger bore and thread on caps. And does anyone have a part number for the disc/disc valve?
 
TURNA

TURNA

Geezer
Jul 24, 2009
8,257
113
Socialist NY
What booster do you have single or double
 
TURNA

TURNA

Geezer
Jul 24, 2009
8,257
113
Socialist NY
Not sure if ACDelco 18M974 will fit that style booster. It does fit the dual diaphragm version
 
roger1

roger1

Master Mechanic
Aug 23, 2010
383
63
San Angelo, TX
Not sure if ACDelco 18M974 will fit that style booster. It does fit the dual diaphragm version
I can't see a reason it wouldn't work. But he says he wants a screw-on cap. I don't see the big deal about that. It is a little harder to R&R the big cap but it's not like it needs to be done very often since you don't need to remove the cap to check the fluid level.
 
TURNA

TURNA

Geezer
Jul 24, 2009
8,257
113
Socialist NY
78-80 uses a different master than 81- and up
 

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