4 Wheel Disc Brake Conversion

57 Handyman

Greasemonkey
Feb 6, 2017
201
43
SSN696, if the question regarding foot pedal or hand brake, my 87 EC has an e'brake foot pedal.

Abbey, thanks for sharing feedback and your experience. I'll likely do just the prop valve alone first and, if necessary, add the adjustable valve later.
 

abbey castro

Master Mechanic
Oct 31, 2015
433
93
Harker Hts TX
SSN696, if the question regarding foot pedal or hand brake, my 87 EC has an e'brake foot pedal.

Abbey, thanks for sharing feedback and your experience. I'll likely do just the prop valve alone first and, if necessary, add the adjustable valve later.
Yup, don't go changing stuff until you start with the proportioning valve and go from there.
 
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ssn696

Living in the Past
Supporting Member
Jul 19, 2009
5,120
113
Permanent Temporary
This may not be the optimal solution for you, but here is the solution I used. A few pages back, there is a diagram.


Scroll down a bit to find the brake cable bracket solution. The little D-shaped brackets adapt the cable ends to the parking shoe levers.
 
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81cutlass

Comic Book Super Hero
Feb 16, 2009
3,720
113
Western MN
In 83 GM changed their master cylinders from small pilot to large pilot so a pre 83 master will fit on a 86+ car but not the other way around. I prefer a later 80's B body caprice master over the 79-81 WS6 Trans am because it's aluminum body with the better plastic rubber seal lid vs. the cast iron T/A one (looks more factory) and the pilot bore is the correct size where it mates into the booster. Other options are late 90's early 2000's RHD postal S10 master's and mid 90's Impala SS but you need to reflare the brake lines at the master. The late 80's B body caprice wagon master jus needs the front and rear lines flipped at the master, its a direct bolt on part and fixed my issue. Willwood and other aftermarket companies also make ones that work but I prefer to put OEM type parts in my stuff because you can get replacements at parts stores if they crap out when you are away from home.

I noticed poor brake pedal feel when I put rear blazer disks on my stock master 86 car. I tried swapping the proportioning valve firs and it didn't do anything and the valve started leaking very quickly. If you have poor pedal feel (it's squishy and seems to have too much pedal feel) you need a larger bore master. Rear disks take more fluid volume so you need a large bore master.

For what its worth I suggest keeping the stock proportioning valve until you get the pedal feel fixed. The valve will make the rear brakes apply at a different force relative to the front brakes so the time to swap that is if you are going 55mph and stomp the brakes and the rear brakes don't lock up when the front ones do or vice versa. But it won't do anything for pedal feel. I'm not a huge fan of aftermarket disk/disk prop valves anyways, most people that put disk conversions on their cars are running large wheels and tires or pair it with larger front brakes, along with changing the weight bias due to engine swaps. If you don't like how the front/rear bias is with the stock prop valve I'd go to the adjustable willwood piece (summit has a store brand that's 1/3 cheaper also just without the wilwood logo but the same piece).
 
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64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
3,800
113
Upstate NY
Yup, don't go changing stuff until you start with the proportioning valve and go from there.
I respectfully disagree with this only because some of the needed information is not included. There is a difference between an S10 and C5/C6 and Z06 caliper fluid capacities. I agree that an S10 front caliper will work with a stock master and a proportioning valve swap is recommended. But that same master cylinder will apply a C5/C6 brake about 2" from the floor. and the stock proportioning valve will work fine with a metric rear caliper upgrade only because the proportion of fluid needed between the front and rears is very similar to the stock brakes if a larger bore master cylinder is used.

Really need to know every part that is going to be installed.
 
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