Question about '86 master cylinder and booster swap

Willybill32

Active Member
Jul 16, 2019
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87
38
Lexington, KY
I have a 1986 Mustang GT 5.0/5 speed. The car sat inside for at least the past 12 years or so. About nine years ago I re-did the suspension, including swapping in a front suspension from an '87-'93, new shocks/struts, new springs and a rear disc conversion kit from Stainless Steel Brake Corp. According to SSBC's catalog at the time, their '86 kit worked with the stock master cylinder, and that's what I have, and the stock proportioning valve is still in place. After all this time, I have the engine freshened up and back in the car, and I've had an opportunity to drive it.

I'm finding the brakes are not nearly as strong as I expected, and the pedal isn't as firm as I'd like. I'm looking about a master cylinder swap, and I'm seeing all kinds of recommendations in the posts I've read, including the '86 Mustang SVO master cylinder (1 1/8" bore), '93 Cobra master cylinder (1" bore), '94 master cylinder (15/16' bore). and more talk about the brake booster. I now realize I need, at a minimum, to remove the stock proportioning valve. Can anyone give me any insight on what is the most appropriate bore size and master cylinder to use? If I use a new master cylinder, do I need to change the booster? If so, to what?
 
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Noobz347

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I'm finding the brakes are not nearly as strong as I expected, and the pedal isn't as firm as I'd like.

This sounds like you may still have air trapped in the system.

If your cylinder or booster is under size the pedal should be stiff as hell (and [then] stopping power or lack thereof would come into play).
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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You need to gut the proportioning valve and I would add a adjustable proportioning valve.
Here is some help:
And:
I should ask, 4 lug or 5?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
18,569
6,094
193
polk county florida
Are you picking on me today?
Someone crash your toy helicopter again?
Is your little rc race car stuck in the middle of that frozen lake again?
Or are you just picking on me?
 
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Willybill32

Active Member
Jul 16, 2019
200
87
38
Lexington, KY
You need to gut the proportioning valve and I would add a adjustable proportioning valve.
Here is some help:
And:
I should ask, 4 lug or 5?
It's still 4-lug.

Regarding the link immediately above your question:

Screen Shot 2020-02-01 at 7.53.25 AM.png
 

Rdub6

So while I wait to figure out my rear end issues
Dec 29, 2017
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try this link

 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
18,569
6,094
193
polk county florida
Lots of stuff in here.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
34,667
10,836
224
Massachusetts
The SSBC is pretty much a 93 Cobra rear setup right? Not sure why they would claim it would work with stock MC?

Anyway, with front stock 60mm calipers and rear 45mm calipers from the 93 cobra, you want the 1” bore MC. On an 86, the fittings are SAE, so ah easier swap is to use an 85 town car MC as its also 1” bore.

Booster is optional. You might want the added assist, or not. Depends on your leg strength and personal preference.

Oh any as soon as any non-stock brake setup is placed on a car, you need to gut the stock prop valve and install and adjustable
 
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Willybill32

Active Member
Jul 16, 2019
200
87
38
Lexington, KY
You need to gut the proportioning valve and I would add a adjustable proportioning valve.
Here is some help:
And:
I should ask, 4 lug or 5?
Thanks, General karthief!
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
18,569
6,094
193
polk county florida
Don't thank me, thank @Mustang5L5
He put in the time and effort to give us this resource, as did many other members that contributed to the technical/how to threads here that help to make me look like a mechanical hero.
 

Willybill32

Active Member
Jul 16, 2019
200
87
38
Lexington, KY
The SSBC is pretty much a 93 Cobra rear setup right? Not sure why they would claim it would work with stock MC?

Anyway, with front stock 60mm calipers and rear 45mm calipers from the 93 cobra, you want the 1” bore MC. On an 86, the fittings are SAE, so ah easier swap is to use an 85 town car MC as its also 1” bore.

Booster is optional. You might want the added assist, or not. Depends on your leg strength and personal preference.

Oh any as soon as any non-stock brake setup is placed on a car, you need to gut the stock prop valve and install and adjustable
Thanks, Mustang5L5!

My ‘86 has the stock booster. Is it adequate for the new master cylinder?
 

Willybill32

Active Member
Jul 16, 2019
200
87
38
Lexington, KY
The SSBC is pretty much a 93 Cobra rear setup right? Not sure why they would claim it would work with stock MC?

Anyway, with front stock 60mm calipers and rear 45mm calipers from the 93 cobra, you want the 1” bore MC. On an 86, the fittings are SAE, so ah easier swap is to use an 85 town car MC as its also 1” bore.

Booster is optional. You might want the added assist, or not. Depends on your leg strength and personal preference.

Oh any as soon as any non-stock brake setup is placed on a car, you need to gut the stock prop valve and install and adjustable

Mustang5L5, my apologies that I keep getting lost in the forum threads...but I posted a question to you on another thread where you recommended the use of a 1985 Lincoln Town Car master cylinder on an '86 Mustang GT, and I'll post the same question here.

I purchased the '85 Town Car master cylinder. I was hoping for aluminum, but got cast iron, but guess that doesn't matter. The new master cylinder came with a new pushrod. Do you have experience with whether or not I need to replace the original pushrod with the new one, or is there enough adjustment on the original pushrod to allow me to reuse it?

Thanks in advance!
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
34,667
10,836
224
Massachusetts
You shouldn't need to swap the pushrod. You do need, however, to measure that the pushrod makes proper engagement with the MC's piston. It can' extend out too far, or not be close enough.
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
29,860
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Box behind Walmart
www.stangnet.com
my apologies that I keep getting lost in the forum threads.


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