brake distribution block help

[signorc 31]

Hi all, 

Upgraded to front disks from a 1978 Granada.  The car brakes fine. Thought I was going to get just a little bit more shorter stopping distance so I'm thinking the brake distribution block may not be correct.

Here's a pic of how it's set up.  Could I please have some feedback?

The valve's number is C8ZA-2B257-M

All the best & THANK YOU!

Paul

[Rsanter 152]

What it looks like you have there is the typical drum/drum dist block.

if you want to do it the easy way you can remove the line going to the rear brakes. Install a short hardline that will go to the inlet port of an adjustable prop valve. These can be had from summit racing for reasonable cost.

then connect the exsisting hard line to the rear brakes to the output of the adjustable prop valve.

[aslanefe 333]

When you brake, does the rear or front tires lock up first? You can test it on a gravel road.

[barnett468 418]

you need a combo valve from a 70 with disc brakes to do it properly and safely.

 

[Mike65 475]

Here is a link to an adjustable one from Summit Racing. https://www.summitracing.com/parts/ssb-a0707-1/overview/

Here is a link to the factory one from Tony Branda Mustang/Shelby parts. http://www.cobranda.com/19dibrprvaan.html

I purchased the same one from Branda for my 69 Coupe when I converted to disc brakes, but have not driven it yet.

[signorc 31]

Thanks for all your input. I did forget to say that I did install an adjust prop valve.

It just seems that when I test the brakes by speeding up and breaking after 5 or 6 runs the brakes drag on a bit too much before coming to a complete stop.  would adjusting the master cylinder rod help?

[barnett468 418]

8 minutes ago, signorc said:

Thanks for all your input. I did forget to say that I did install an adjust prop valve.

It just seems that when I test the brakes by speeding up and breaking after 5 or 6 runs the brakes drag on a bit too much before coming to a complete stop.  would adjusting the master cylinder rod help?

yes, your rod may be depressing the master a little. there should be around .015" clearance between the end of the rod and the master piston. am adjustable prop rod is nothing like the factory valve and they are in fact a little dangerous to use by themselves on front disc brake rear drum brake set ups.

[signorc 31]

Thanks Barnett468.  So the best way to go is by installing a new disk/drum brake dist block? is the one Mike65 suggested above good or would you suggest another?

 

[aslanefe 333]

Can you lock the front and or rear tires when you brake?  What does drag on mean in your statement of "after 5 or 6 runs the brakes drag on a bit too much before coming to a complete stop"? Do you mean brakes are locking up or do you mean the stopping distance increases after 5 or 6 runs (but brakes don't lock up)?

[barnett468 418]

10 hours ago, signorc said:

Thanks Barnett468.  So the best way to go is by installing a new disk/drum brake dist block? is the one Mike65 suggested above good or would you suggest another?

 

yes the 69 tony branda one will work but the 70's are slightly different if i recall correctly.

[signorc 31]

I tried decreasing the adj prop valve which is located near the rear axle all the way and then increased it all the way and I didn't see much a difference in breaking distance.

To answer aslanefe's question.... the brakes do NOT lock up.  The stopping distance increases a little after a few hard stops traveling 50 mph.

I guess I was expecting the stopping distance to be more like a my toyota....but then again my toyota's weight is a lot less than the mustang.

Does anyone think the stock prop valve makes a big difference in the stopping distance? compared to having an adj prop valve at the back of the car?

thanks again for all your input & ideas!

[aslanefe 333]

You should be able to lock up the wheels when you step on the brakes real hard, if you can't then it means you are not applying enough pressure to your brake pistons and your stopping distance will be longer. I think your problem is with master cylinder. I do not think changing the proportioning valve is going to help you.  Increasing braking distance after a few hard stops points to brake fade (due to pads and rotors heating up). What I know of prop valves is; it's job is to adjust the proportions of brake line pressure between front and rear wheels so they lock up at the same time or close to each other (not one side locking up only). Usually the rear of the car is lighter so the rear brakes lock up first, prop valve limits the pressure to rear to prevent it locking up too early (before front wheels).

Stock prop valve is designed to work with stock drum brake cylinder, stock master cylinder diameter and stock disk piston diameter stock disk diameter etc. If you alter one of these, stock prop valve won't work right (this is where adjustable prop valve comes in handy).

Do you have a power booster? What is the bore size on your master cylinder? What size piston the disks have and what size piston on rears?

[danno 128]

I have factory power disc setup.   I have never been able to lock the front tires. Tried new master and disti block in a 69.  How easy is it to lock the front brakes on a 69 with actory disc brakes and drum rear? 

[barnett468 418]

21 minutes ago, danno said:

I have factory power disc setup.   I have never been able to lock the front tires. Tried new master and disti block in a 69.  How easy is it to lock the front brakes on a 69 with actory disc brakes and drum rear? 

there is a problem with your system.

 

[signorc 31]

Thank you for your explanation aslanefe.  I follow everything you say. 

To answer your questions:

-I do have a power booster

- I have no clue what bore size my master cylinder is.  Purchased the conversion kit from SSBC.  

- I have the 60mm 1 piston caliper with disk in the front 

- I have drum brakes in the rear.  Do they have different size options for rear brake cylinders?

PS - I've NEVER been able to lock either front or rear wheels

[barnett468 418]

43 minutes ago, signorc said:

Thank you for your explanation aslanefe.  I follow everything you say. 

To answer your questions:

-I do have a power booster

- I have no clue what bore size my master cylinder is.  Purchased the conversion kit from SSBC.  

- I have the 60mm 1 piston caliper with disk in the front 

- I have drum brakes in the rear.  Do they have different size options for rear brake cylinders?

PS - I've NEVER been able to lock either front or rear wheels

there is a major problem with your system.

[signorc 31]

hahahah lol I love comments like the last one by barnett468 :) 

besides telling me what I already know. would you have any insight on how to resolve my "major problem"?

[barnett468 418]

2 minutes ago, signorc said:

hahahah lol I love comments like the last one by barnett468 :) 

besides telling me what I already know. would you have any insight on how to resolve my "major problem"?

i will be back in a few hours but what is stock ford on your system and what is not?

[signorc 31]

it was born with 4 drums. the rear is still all original drums with new cylinders, drums & pads.

i converted to front disks with a conversion kit from SSBC.

They gave me 1978 granada spindles with the typical 1 piston caliper from a Mustang, Cougar or Torino.

I added the adj prop valve to the rear brake line.  and installed the new booster & master cylinder. It's almost midnight here in Italy so I'll read your response tomorrow mornin.  Goodnight :)

[aslanefe 333]

Instead of changing parts and hoping to solve the problem, I would start by measuring the hydraulic pressures on calipers and rear cylinders. They sell a pressure gauge you attach in place of the bleeder valve. 

[barnett468 418]

1 hour ago, signorc said:

it was born with 4 drums. the rear is still all original drums with new cylinders, drums & pads.

i converted to front disks with a conversion kit from SSBC.

They gave me 1978 granada spindles with the typical 1 piston caliper from a Mustang, Cougar or Torino.

I added the adj prop valve to the rear brake line.  and installed the new booster & master cylinder. It's almost midnight here in Italy so I'll read your response tomorrow mornin.  Goodnight :)

italy, wow, been to part of there once. very nice.

please answer these questions one at a time.

 

what year is your car?

did you install a disc brake pedal?

exactly what brake booster is it?

what engine?

does it have a rough idle like it has a big cam.

is the booster working?

did you check the booster for leaks?

does it require a lot of force on the brake pedal to do a moderately fast stop and feel like there is no power brakes?

did you check the clearance between the booster rod and the master cyl piston?

did you install the same size rear wheel cylinders that you took out?

do you have a disc brake master cylinder?

about how far does your brake pedal travel once it just barely begins to engage the brakes, 1",  2", 3", 4" ?

not worrying about the fact that you can not lock the brakes up, does it at least stop well enough that it is safe to drive or do you have to use 2 feet on the brake pedal and pray it will stop in time?

 

 

 

 

 

 

 

 

[aslanefe 333]

5 hours ago, danno said:

I have factory power disc setup.   I have never been able to lock the front tires. Tried new master and disti block in a 69.  How easy is it to lock the front brakes on a 69 with actory disc brakes and drum rear? 

Danno, step on the brake as hard as you can on a gravel or dusty road; fronts should lock too (after the rears lock). I believe, with modern better gripping tires, the original prop valve is not working right, limiting the pressure to rears with an adjustable prop valve and adjusting it to lock both front and rear at almost same time is the way to go. Pad and shoe material, conditions of the disks and drums play a role too on which side locks up first.

[barnett468 418]

1 hour ago, aslanefe said:

Danno, step on the brake as hard as you can on a gravel or dusty road; fronts should lock too (after the rears lock). I believe, with modern better gripping tires, the original prop valve is not working right, limiting the pressure to rears with an adjustable prop valve and adjusting it to lock both front and rear at almost same time is the way to go. Pad and shoe material, conditions of the disks and drums play a role too on which side locks up first.

nope, tires have zero affect on how a factory prop valve works.

gravel roads are nearly useless for testing.

you must absolutely positively run a factory type combo valve with disc drums for the safest operation.

you should never, ever, ever, run only an adjustable prop valve on disc drum brakes unless you don't care about possibly killing yourself and/or others.

 

 

 

 

 

 

[aslanefe 333]

2 hours ago, barnett468 said:

nope, tires have zero affect on how a factory prop valve works.

gravel roads are nearly useless for testing.

you must absolutely positively run a factory type combo valve with disc drums for the safest operation.

you should never, ever, ever, run only an adjustable prop valve on disc drum brakes unless you don't care about possibly killing yourself and/or others.

 

 

 

 

 

 

I did not say tires affect how prop valve works, prop valve does not care about tires or piston diameter, it just limits the fluid pressure applied by the master cylinder.  If you have bold hard tires on the back and soft sticky tires on the front with factory prop valve, which tires lock first, front or back? How about sticky tires on the back, bold on the front, which ones will lock first?

[danno 128]

I tried jamming on the brakes years ago on wet asphalt.  The rear brakes locked up, I could not get the front to do it.  Again, my system is all factory except for a new master cylinder. I am the 3rd owner of the car since new, I bought it in 1982 with  60,000 miles on it, so I am pretty sure it is all factory stuff.    I have tried at least 3 masters, even a brand new one from Ford. I did put a new kit in the proportioning valve a year ago, but the results seem to be the same, although I have not tried locking them up again.  I still wonder.  Maybe it is time to put a pressure gauge on the wheels, as suggested?