Question about '86 master cylinder and booster swap

Willybill32 · Jan 31, 2020

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?

Noobz347 · Jan 31, 2020

Willybill32 said:
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).

Willybill32 · Jan 31, 2020

Thanks!

General karthief · Jan 31, 2020

You need to gut the proportioning valve and I would add a adjustable proportioning valve.
Here is some help:

Brakes - The Ultimate 4-lug/5-lug Brake Conversion/upgrade Thread

Starting this thread with the hopes of reducing the number of 5-lug or general brake upgrade threads that have been appearing on the forums since most of the major brake conversion sites have gone down. This thread will be strictly informational, and any off-topic banter or user specific...

www.stangnet.com

And:

https://www.stangnet.com/mustang-forums/threads/93-cobra-boosters-dont-get-taken-for-a-ride.914282/quote

I should ask, 4 lug or 5?

Noobz347 · Jan 31, 2020

General karthief said:
I should ask, 4 lug or 5?

General karthief · Jan 31, 2020

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?

Noobz347 · Jan 31, 2020

General karthief said:
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?

A little but only because you're doing what I do sometimes. Speed read and crash. LoL

Willybill32 · Feb 1, 2020

General karthief said:
You need to gut the proportioning valve and I would add a adjustable proportioning valve.
Here is some help:

Brakes - The Ultimate 4-lug/5-lug Brake Conversion/upgrade Thread

Starting this thread with the hopes of reducing the number of 5-lug or general brake upgrade threads that have been appearing on the forums since most of the major brake conversion sites have gone down. This thread will be strictly informational, and any off-topic banter or user specific...

www.stangnet.com

And:

https://www.stangnet.com/mustang-forums/threads/93-cobra-boosters-dont-get-taken-for-a-ride.914282/quote
I should ask, 4 lug or 5?

It's still 4-lug.

Regarding the link immediately above your question:

Rdub6 · Feb 1, 2020

try this link

93 Cobra Boosters - Don't Get Taken for a Ride

What is the deal with the local parts store selling what they call a brake booster for a 93 cobra for 100$???? I know this cannot be right but what is it? Does anyone know? Has anyone bought one? I asked them to pull up one for my car and it was around the same price, and most of the part...

www.stangnet.com

General karthief · Feb 1, 2020

Progress Thread - Technical Thread/how-to Index

Guys, if "that should be a sticky," then please reply to this thread with the link to your suggestion and why you think it should be added. How to determine if a thread should be included: - Does the topic address a common fox 5.0 owner's needs? / Is it a frequently asked question? / Is it...

www.stangnet.com

Lots of stuff in here.

Mustang5L5 · Feb 1, 2020

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

Willybill32 · Feb 1, 2020

General karthief said:
You need to gut the proportioning valve and I would add a adjustable proportioning valve.
Here is some help:

Brakes - The Ultimate 4-lug/5-lug Brake Conversion/upgrade Thread

Starting this thread with the hopes of reducing the number of 5-lug or general brake upgrade threads that have been appearing on the forums since most of the major brake conversion sites have gone down. This thread will be strictly informational, and any off-topic banter or user specific...

www.stangnet.com

And:

https://www.stangnet.com/mustang-forums/threads/93-cobra-boosters-dont-get-taken-for-a-ride.914282/quote
I should ask, 4 lug or 5?

Thanks, General karthief!

Willybill32 · Feb 1, 2020

Rdub6 said:
try this link

93 Cobra Boosters - Don't Get Taken for a Ride

What is the deal with the local parts store selling what they call a brake booster for a 93 cobra for 100$???? I know this cannot be right but what is it? Does anyone know? Has anyone bought one? I asked them to pull up one for my car and it was around the same price, and most of the part...

www.stangnet.com

Thank you!

General karthief · Feb 1, 2020

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 · Feb 1, 2020

Mustang5L5 said:
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?

General karthief · Feb 1, 2020

go back and read the third paragraph.

Willybill32 · Feb 13, 2020

Mustang5L5 said:
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 · Feb 13, 2020

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.

Willybill32 · Feb 13, 2020

Mustang5L5 said:
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.

Thank you!

Noobz347 · Feb 13, 2020

Willybill32 said:
my apologies that I keep getting lost in the forum threads.

If you ever forget where you put something, look in here:

In Red:

Click on your screen name in the upper right
Click on (Your Content)
This will show all of the places in which you interacted.

The one circled in Yellow is is the Bookmark tab. You should play with that and see how it operates. It will help too.

Question about '86 master cylinder and booster swap

But at least it's tight!

Stangnet Facilities Maint Tech... Er... Janitor

But at least it's tight!

wonder how much it would cost to ship you a pair

Stangnet Facilities Maint Tech... Er... Janitor

wonder how much it would cost to ship you a pair

Stangnet Facilities Maint Tech... Er... Janitor

But at least it's tight!

So while I wait to figure out my rear end issues

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

But at least it's tight!

But at least it's tight!

wonder how much it would cost to ship you a pair

But at least it's tight!

wonder how much it would cost to ship you a pair

But at least it's tight!

That is…until I whipped out my Bissell

But at least it's tight!

Stangnet Facilities Maint Tech... Er... Janitor

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