Aftermarket Brake and Clutch Master How-To

Upgrades, downgrades, modernizations, alterations or just being creative.

Postby yitzac1990 » Sun Jun 09, 2019 10:49 am

Hello all! One of the many things I am doing to my 1969 patrol is upgrading the braking system, as well as a V8 swap. The V8 swap requires a larger bore clutch master cylinder than stock, and instead of paying $60 for a Wilwood, I found an "OEM-type" master cylinder that works for about $26, and has the correct mounting bolt spacing of 2.25"! I also want to use Chevy truck brakes (disc swap eventually), so I wanted a large, tandem brake master cylinder as well. I installed both cylinders at the same time and actually took pictures for once, so I figured I would share the knowledge with everyone here. First, a parts list:

BMC: 1990 Chevy C1500 truck (Cardone p/n 132352)
CMC; 1980 Jeep CJ5 or 7 (Dorman p/n CM106439)
1.5" tubing (similar to roll cage tubing, dont need very much of it)
1.5" tubing exhaust flange, 2-bolt
2.5" (I think? more detail below) exhaust tubing flange, 2-bolt
2.5" tubing (very short section)
1/4" steel flat plate (I think the piece I used was 2" x about 2.5")

Besides the master cylinders of course, I had all the materials laying around my shop. It took a few hours of figuring out what/how to do things, but it turned out great I think. If I had a more appropriately sized flange for the BMC (you'll see), it could have turned out better, but that would have been extra time and money, and I have my scrap piles of metal so I can use them, so I used what I had! On to the procedure, see next posts:
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Postby yitzac1990 » Sun Jun 09, 2019 10:51 am

Here is a comparison of the OEM and Jeep clutch master cylinders:

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The first thing youll notice, is the push rod is a lot longer, and has an eyelet at the end. This wont do, so the first step is to swap the push rods:

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If you dont know how to remove a CMC push rod, its very easy. There is just a c-clip on the inside bore of the MC holding a conical washer in place. Get the clip out, and out comes the conical washer and push rod! Here is a comparison of the "head" of both push rods. They are VERY similar in size and shape, and will work perfect! P.S. - when searching for a CMC to use, I only had 2 things to go off of - the bore and mounting bolt spacing. So I took a bit of a risk in buying this one, because I didn't know if the OEM push rod would swap into this CMC. But it works, so I picked a good MC!

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I had to get the larger washer of the jeep MC onto the patrol push rod. This required cutting the eyelet off (not going to be using that push rod anyways). Easy peasy.

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Next, put the jeep conical washer on the patrol push rod, put the assembly into the jeep CMC, and put the Jeep c-clip back on to hold it all together.

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Here is the completed master cylinder, ready to be installed:

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NOTES: I hadn't realized this until I went to re-install the new CMC, but apparently a previous owner drilled a second set of holes in the clevis for the pedal pin. When I tried to fit it up, I had to push the rod in a bit to get the pin in. After I realized this, I spaced out the CMC from the mounting face using a few washers on each stud. Once I get the engine/trans in place, it will be much easier to see how well it actually works!

I also had to take a dremel sanding wheel to the center opening and enlarge it a bit to fit this jeep CMC with its rubber boot.
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Postby yitzac1990 » Sun Jun 09, 2019 11:02 am

Here is a comparison of the OEM and chevy brake master cylinders:

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Honestly, I didn’t realize how big the chevy BMC would be! I think it will be able to stop this patrol no problem! Did a little test fitting, holding it in place:

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Nope, that’s not going to work, it is hitting the CMC and still isn’t centered on the hole. Let’s move it out a bit more:

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I think I can live with that, and it will still have no problem fitting under the hood or anything like that. Skipping ahead a few steps, and we end up with this adapter piece. From left to right, we have: 2.5” exhaust flange -> 2.5” exhaust piping (about 1.5” long) -> 2”x2.5” ¼” steel flat bar (with a 1.5” hole cut in the center of it) -> 1.5” roll cage tubing (about 6” long?) -> 1.5” tubing exhaust flange.

The 1.5” exhaust flange just so happened to have the perfect bolt spacing and fit right on the patrols mounting studs with no modifications needed! I was so happy to realize this, and it made things so much easier!

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If you look closely, you’ll see here that I had to notch out the mounting holes on the BMC – this is why I said a more appropriately sized (slightly smaller) flange at this end would have been better, but I simply didn’t have one.

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The next thing I had to do was make a push rod long enough for this setup. First, I took some old CMC rubber boots that I found on some old Nissan CMCs, put some liquid nails on them, and inserted them into this adapter, as you can see. This is to keep the push rod centered in the adapter when everything is apart, to ensure alignment when assembling everything. It turned out perfect!

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Here is the adapter and push rod. Fun fact of the day: the center section of that push rod is made from the “spacer” used on a rear sway bar end link from this Patrol!

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Another shot of the adapter:

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Final install photos:

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BONUS: While I was at it, I took off the pedal stop bracket, welded a nut in place of the rubber stopper for the brake pedal, and can now use a Nissan 240sx brake light switch here! So no more pressure activated switch!

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Postby RiverPatrol » Sun Jun 09, 2019 11:44 am

Thanks for putting this together. :D
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Postby yitzac1990 » Sun Jun 09, 2019 12:21 pm

no problem! and if anyone is interested in more details, i can get more accurate dimensions of the BMC adapter and all that.
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Postby MadTripper » Sun Jun 09, 2019 6:55 pm

Nice job and write up!
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Postby Esteban » Mon Jun 10, 2019 9:09 am

Excellent work, descriptions, and photos. :clap: :clap: :clap:

Is the brake master cylinder a 1"?
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Postby yitzac1990 » Mon Jun 10, 2019 2:02 pm

IIRC, its 1-1/8" But I think you can get smaller bore cylinders for the same vehicle, that should bolt up just the same.
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Postby Esteban » Mon Jun 10, 2019 6:43 pm

Thanks for the info. But then I have the conern that you’ll have to excert like 25% more force at the pedal to apply the same pressure at the wheel cylinders.

Are you ok with it?

If you install disk brakes, it will be a problem since they need more force at the pedal for the same braking effort than drums.

Easily solved if you install a booster. You’ll have to enlarge the mounting pipe assembly that you just showed us earlier.
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Postby yitzac1990 » Tue Jun 11, 2019 8:31 am

well everything on the patrol is changing, so I figure it may not be perfect right off the bat. I will just have to see how it feels once I get everything up and running. If I need to add a booster, I can worry about that later. and you're right, the adapter I made will most likely have to be modified, which shouldn't be a big deal.
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Postby Esteban » Tue Jun 11, 2019 9:01 am

yitzac1990 wrote:well everything on the patrol is changing, so I figure it may not be perfect right off the bat. I will just have to see how it feels once I get everything up and running. If I need to add a booster, I can worry about that later. and you're right, the adapter I made will most likely have to be modified, which shouldn't be a big deal.


Sorry I got side tracked and only thinking in the original setup when I made my comment. Everything will be changing, so you have a good starting point there.
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