FYI FORD - MustangSteve's Ford Mustang Forum
The Internet's Most Knowledgeable Classic Mustang Information
IF YOU HAVE A QUESTION ABOUT CLASSIC FORD MUSTANGS, YOU HAVE COME TO THE RIGHT PLACE!
MustangSteve has over 30 years of Mustang experience, having owned 30 of them and restored several others. With the help of other Mustangers, this site is dedicated to helping anyone wanting to restore or modify their Mustang.... THERE ARE NO DUMB QUESTIONS!!!!!
Visit MustangSteve's web site to view some of my work and find details for:
FYIFORD Contributors' PICTURES - Power Brake Retrofit Kits for 65-66 Stangs - Classic Mustang FAQ's by MustangSteve - How to wire in a Duraspark Ignition - Mustang Ride Height Pictures and Descriptions - Steel Bushings to fit Granada Spindles to Mustang Tie Rods - Visit my EBAY store MustangSteve Performance - How to Install Granada Disc Brakes MustangSteve's Disc Brake Swap Page - FYIFORD Acronyms for guide to all the acronyms used on this page - FYIFORD Important information and upcoming events

You are not logged in. Would you like to login or register?

8/31/2017 9:19 AM  #1


1970 Mustang - brakes not performing

So I have a 1970 Mustang.  It came with drum/drum non-power brakes.  I upgraded the front to stock disc brakes with an appropriate master cylinder and prop valve.  I expected to be able to feel a difference... no, not really.  I've bled them over and over.  Still not feeling it.  The brakes don't lock up at all. 

So, before I go and yank it all off, I wanted to know if there is anything I should be looking for that could cause this issue? 

 

8/31/2017 9:40 AM  #2


Re: 1970 Mustang - brakes not performing

Going to need more information.  Where are the brakes from?  Did you buy a complete kit or piece it together?  Is it manual or power brakes?  What proportioning valve did you use?

 

8/31/2017 10:34 AM  #3


Re: 1970 Mustang - brakes not performing

What master cylinder are you using, the diameter of the cylinder with a manual set up is very important. If it is too big you won't be able to generate the pressure needed for safe operation.


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

8/31/2017 2:17 PM  #4


Re: 1970 Mustang - brakes not performing

If your distribution block has an electric fitting in it, you most probably have inadvertently moved the internal slide valve into position to block off or severely restrict brake fluid to the rear drums.  If you are lucky you can remove the electric sender unit and reset the slide valve with a pick.  An illustration of the distribution block such as the one in the shop manual would be helpful; however I no longer have anything available.  Possibly you can find something on line.
Best
Al


Classic cars are full of surprises and almost none of them are good ones!
 

8/31/2017 6:56 PM  #5


Re: 1970 Mustang - brakes not performing

Non-power brakes.  I procured stock 1970 spindles.  I bought everything else new (I'm sure the calipers were rebuilds).  Master cylinder is 1". Prop valve is an adjustable SSBC unit.

Last edited by jcmeyer5 (8/31/2017 7:39 PM)

     Thread Starter
 

8/31/2017 7:55 PM  #6


Re: 1970 Mustang - brakes not performing

jcmeyer5 wrote:

Non-power brakes. I procured stock 1970 spindles. I bought everything else new (I'm sure the calipers were rebuilds). Master cylinder is 1". Prop valve is an adjustable SSBC unit.

When I did my MKII rear brake conversion I used the MS from the Lincoln. The conversion was not satisfactory as far as stopping the car better than with the rear drums. I bought a brake pressure gauge to check the PSI I was getting at the front and rear calipers and found that the pressure generated by the MKII MS was way low, it was 1 1/8". I swapped the Lincoln MS for a stock 68 1" and got the stopping power I needed.
 Rather than guessing the problem  why don't you try checking the pressures generated at each caliper to pinpoint the problem.


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

9/01/2017 4:47 AM  #7


Re: 1970 Mustang - brakes not performing

All factory disc cars had power brakes, so if you are using a stock master cylinder that's your problem.  Also, worth noting it needs to be a disc/drum master because a drum/drum master won't work either.  The fluid volume and pressure required for discs is significantly higher than for drums (why disc/drum masters always have a bigger chamber for the front brakes). 

The proportioning valve is an adjustable unit, but what about the stock valve?  If you're using a stock '70 part it's a combination valve that incorporates both the distribution block and the proportioning valve.  To run an external proportioning valve you need to gut the proportioning part of the valve.  You leave the shuttle valve intact so it preserves your braking in the event of a hydraulic failure in either the front or rear brakes. 

 

9/01/2017 6:44 AM  #8


Re: 1970 Mustang - brakes not performing

The master cylinder is a disc/drum master cylinder.  I took the time to research as I wanted an aluminum one.  I don't remember the exact application, but it was a manual disc/drum application.

The adjustable prop valve has replaced the stock one.  Can I post a link?  Didn't want to break any rules in my first few posts.

     Thread Starter
 

9/01/2017 3:30 PM  #9


Re: 1970 Mustang - brakes not performing

Best thing is a picture of the valve.
I would suggest using the 15/16" master cylider. MustangSteve has them.  It will increase the line pressure to get the correct amount for manual disc/drum.
Another thing is pad material. If you bought the best lifetime warranty pads you could find at the local auto supply store, they are not going to lock up the brakes. You are better off using the cheapo pads from OReilly. They won't last as long, but will stop better.

Be sure the port on the mc closest to the firewall is plumbed to the front brakes.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

9/01/2017 8:42 PM  #10


Re: 1970 Mustang - brakes not performing

Here is the distribution block/prop valve combo:
http://ssbrakes.com/images/F118717021.jpg

I think I will look for a brake line pressure kit.  Oh... I had originally installed a 74 Maverick MC, but later switched to an aluminum MC from an 84 SVO.

     Thread Starter
 

9/02/2017 9:56 AM  #11


Re: 1970 Mustang - brakes not performing

The '84-'86 Mustang SVO MC has a 1-1/8" diameter bore. That MC is the same as the MC that came on the '82-'87 Lincoln Town Car and the '84-'90 Lincoln Mk VII.

There was another conventional style MC like that with an aluminum body but with a 1.00" bore diameter that was on the Crown Victorias produced around 1985.

 

9/02/2017 10:47 AM  #12


Re: 1970 Mustang - brakes not performing

I just measured the manual brake master cylinder I took off when I put on the MS power brake conversion. It worked great and measured 15/16 inch. Just like MS said.

 

9/02/2017 10:48 AM  #13


Re: 1970 Mustang - brakes not performing

SVOs had a cast iron master cylinder.  SVOs were also a disc/disc car, making that master less than ideal for a disc/drum system. 

 

9/02/2017 7:02 PM  #14


Re: 1970 Mustang - brakes not performing

Sorry if I keep changing the story on you.  It's been 8 years since I have driven or worked on this car.  My memory is a bit fuzzy as I have changed it around more than twice.

Here is what I DO remember (and what I saw today). I remember that it is 1" bore, from a disc/drum application, somewhere in the late 70s or early 80s.  It has ports on the engine side, and is definitely aluminum. 

I think I am going to heed the advice given earlier and do a pressure check after I bleed them once more (eight years... might as well make sure).

     Thread Starter
 

9/02/2017 8:41 PM  #15


Re: 1970 Mustang - brakes not performing

Pressure check is a great diagnostic test. Once you have that data, you can figure out exactly what to do next.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

9/02/2017 8:58 PM  #16


Re: 1970 Mustang - brakes not performing

I have to agree with MS.  My binders just weren't doing the job they should.  Bought a brake pressure gauge set and found that the most pressure I could muster at idle was 750 psi...way too low for discs.  Checked manifold vac...9.5", also way low for the booster. So with my cam at 6000 feet this just isn't gonna work.  Added mechanical vac pump and a vac tank that took vac from the pump and the manifold.  Problem solved.

You gotta know what's going on or you just keep throwing $$$ at it.

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

9/03/2017 12:01 AM  #17


Re: 1970 Mustang - brakes not performing

Mustang SVO MC --casting, aluminum.

http://www.cjponyparts.com/cardone-select-brake-master-cylinder-new-svo-1984-1986/p/BMC40/


Factory stock SVO Mustang with aluminum bodied brake MC shown mounted in place.

https://assets.hemmings.com/story_image/109333-500-0.jpg?rev=2

There are some replacement cast iron MCs produced for the SVO but, the Continental, SVO and Lincoln Mk VII shared the same brake components and the same MCs and the OEM castings were aluminum.

 

9/03/2017 6:55 AM  #18


Re: 1970 Mustang - brakes not performing

I stand corrected.  SVOs did indeed have an aluminum bodied master cylinder.  I cannot verify if the one from CJ is a reman or new.  If you check Rock Auto, all the masters listed are cast iron. 

The SVO was in many respects a different car than its contemporary Fox bodies.  It used a unique K-member and tubular LCAs among other things.  Apparently it also used an aluminum master cylinder, but of the older style integral reservoir kind.  All the Fox body masters I've seen from the '79-'86 cars were cast iron, and on the later cars they were aluminum, but had a plastic reservoir.  Sort of an oddball master, but that was kind of the SVO's deal, so it makes perfect sense.  With its crossover to the Lincolns it might have simply been sourced from the Ford parts bin to save the cost of a vehicle specific part needing to be made.  Ford did that a lot.

 

Board footera


REMEMBER!!! When posting a question about your Mustang or other Ford on this forum, BE SURE to tell us what it is, what year, engine, etc so we have enough information to go on.