B-Body Master only

[81_El_Homewrecker]

I’ve read a bunch of posts here and have never talked about bore diameter this much in my life. I will try to make this as easy as possible and direct. I want to replace my leaking original master on my 81 El Camino with an upgraded larger bore master. I have a mustang rear disc setup. I can’t figure out if the bbody master I have listed below will physically bolt in place of my current. Thanks guys!

Current Setup
Bore - 0.945”

1990 B-body Master
Bore - 1.125”
Bore diameter (N-1) - 1.575”

 

[TURNA]

What booster do you have single or double?

 

[81_El_Homewrecker]

What booster do you have single or double?

Good question....How do I find out? Can I tell by simply looking at it?

 

[81cutlass]

I think the male pilot of the late caprice master won't fit into the female pilot of the booster. GM changed them in 82 or 83?

I was able to bolt an 88 caprice big bore master to my 86 2+2 but for my 80 century I had to buy a Olds Toronado master.

The bore of the master doesn't matter but the pilot where it slides into the booster is what causes the issue.

 

[TURNA]

Yes is it 12 inches tall or 8ish inches

 

[81_El_Homewrecker]

Yes is it 12 inches tall or 8ish inches

It is the 12” for sure the thing looks massive

 

[81_El_Homewrecker]

I think the male pilot of the late caprice master won't fit into the female pilot of the booster. GM changed them in 82 or 83?

I was able to bolt an 88 caprice big bore master to my 86 2+2 but for my 80 century I had to buy a Olds Toronado master.

The bore of the master doesn't matter but the pilot where it slides into the booster is what causes the issue.

That makes sense...I’m trying to find a larger bore with plastic reservoir. Don’t care if it’s aluminum but that would be preferable.

 

[TURNA]

I prefer the smaller double booster you can get in an 86 Cutlass as well as several other Gbodys

an then install this master

AC DELCO Master Cylinder Part # 89056529 or 18M974 (same master)

 

[81cutlass]

OK, the cutoff is 81

My 80 wagon with the dual diagram booster needed the toronado master. It is steel body but plastic reservoir. Its for disk/disk but works well for my disk/drum car.

The disk/drum riv/toro master is the same as an 81 G body with the small bore. The disk/disk is larger, 1" if rock auto is right.

Raybestos MC39079

If you want the BIG bore caprice you need to get the later booster. I can say the toro master on my car helped a lot with the blazer front disks. The only other big bore master that fits that pre 82 booster is the 2nd gen F body and thats cat iron reservoir.

 

[81_El_Homewrecker]

OK, the cutoff is 81
View attachment 143634

My 80 wagon with the dual diagram booster needed the toronado master. It is steel body but plastic reservoir. Its for disk/disk but works well for my disk/drum car.

The disk/drum riv/toro master is the same as an 81 G body with the small bore. The disk/disk is larger, 1" if rock auto is right.

Raybestos MC39079

If you want the BIG bore caprice you need to get the later booster. I can say the toro master on my car helped a lot with the blazer front disks. The only other big bore master that fits that pre 82 booster is the 2nd gen F body and thats cat iron reservoir.

View attachment 143633

I think I will do the 90 Caprice booster and master as a set like suggested. Both together from advanced are less than $140.