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

[Northernregal]

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]

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.

 

[TURNA]

So is ACDELCO 18M95 the master you wound up using?

 

[64nailhead]

Yes.

 

[MTP-Madmat]

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]

What booster do you have single or double

 

[MTP-Madmat]

What booster do you have single or double

It’s a stock replacement so probably single. What I really want is a bigger bore and screw on cap

 

[TURNA]

Not sure if ACDelco 18M974 will fit that style booster. It does fit the dual diaphragm version

 

[roger1]

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]

78-80 uses a different master than 81- and up