76 master Cylinder port sizes

Tie rods, steering box, drag link, alignment.<br />
What tires fit, brands, sizes, beadlocks, etc.

Moderator: Bfix Staff Members

Post Reply
BroncoJim
BFix Starter
BFix Starter
Posts: 42
Joined: Sat Dec 16, 2006 8:39 am
Location: Atlanta, GA

76 master Cylinder port sizes

Post by BroncoJim » Mon Dec 24, 2012 12:31 pm

Another day another hassle...
I bought a new stock MC for my Bronco. I cleaned it and cleacoated it, bench bled it and when I went to bolt it on I found the port sizes were incorrect. The new ones are too big. I recall this happening before the last time I swapped out the master cylinder (10+ years ago) but I can't recall how. I think I ended up ordering a new one from JBG and it was fine. What a PITA!

Has this happened to anyone else? If it matters I am using Wild Horses stainless brake lines from the master cylinder to the proportioning valve.

TIA,
Jim
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
"If you didn't build it, it's not really yours"

User avatar
Stan
BFix Locked and Loaded
BFix Locked and Loaded
Posts: 3617
Joined: Tue Jun 29, 2004 6:42 pm
Location: Boring Or

Post by Stan » Mon Dec 24, 2012 5:19 pm

I think the last MC i bought came with a couple of adapters/bushings.
Any decent auto parts store should have them in the brake line/parts section.
Stan
When you come to a fork in the road - take it
Homer - " Facts are meaningless . You could use facts to prove anything that's even remotely true."

BroncoJim
BFix Starter
BFix Starter
Posts: 42
Joined: Sat Dec 16, 2006 8:39 am
Location: Atlanta, GA

Post by BroncoJim » Tue Dec 25, 2012 8:20 am

Thanks Stan, I know I can get an adapter but I shouldn't have to.
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
"If you didn't build it, it's not really yours"

User avatar
Stan
BFix Locked and Loaded
BFix Locked and Loaded
Posts: 3617
Joined: Tue Jun 29, 2004 6:42 pm
Location: Boring Or

Post by Stan » Tue Dec 25, 2012 10:35 am

Ya - i agree - you pay good money for something you should at least get all the parts.
Stan
When you come to a fork in the road - take it
Homer - " Facts are meaningless . You could use facts to prove anything that's even remotely true."

carrier6
Bfix Carb'd
Bfix Carb'd
Posts: 148
Joined: Wed Apr 04, 2007 9:00 pm
Location: Damascus, Oregon

Post by carrier6 » Fri Dec 28, 2012 1:56 am

I had the ports on my backwards, after looking at a bunch of them what I found out is it all depends on the manufacturer. Raybestos made the one I needed with the little port in the front and large port on the rear. If that's your set up, I got mine at O'Rielys for $38 brand new. Their part number is MC 83072

BroncoJim
BFix Starter
BFix Starter
Posts: 42
Joined: Sat Dec 16, 2006 8:39 am
Location: Atlanta, GA

Post by BroncoJim » Fri Dec 28, 2012 6:12 am

The one I bought from autozone had the big hole and the little hole where they needed to be but they were too large. When I went and talked to AutoZone about it they told me that sometimes when they rebuild them they will take the port sizes one size over. I responded that this is supposed to be new, not rebuilt. The guy just shrugged...and offered to pay for adapters if I could find some.
It's going back.
I'll try the O'Reillys one Thanks Carrier6
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
"If you didn't build it, it's not really yours"

mhowsmon
Bfix "What's a Bronco?"
Bfix "What's a Bronco?"
Posts: 2
Joined: Tue Jun 02, 2015 7:31 pm
Location: Amarillo, TX

1976 Bronco Brakes

Post by mhowsmon » Tue Jun 02, 2015 7:55 pm

Hey all, been having some trouble with my 76 brakes. Any answers to the following questions greatly appreciated.

Setup - Front Disc / Rear Drum

1) Is there any difference in size of brakes lines from front than rear for?
2) MC - should front brakes hook up to front valve or rear?
3) Bore size, what is the recommended size? I have heard smaller is better braking?
4) Power brakes, assume the vacuum of off of booster provides this? How far should tube from brake peddle push in the MC?

My symptoms are that after bleeding brakes, I can get the drums working pretty well but I am not getting enough brake line pressure the ever engage the disc brakes (brand new calipers). I have bench bled MC, checked and re-checked for leaks. Any advice for good known setup would be greatly appreciated.

Mike
Mike H
1976 Bronco

DirtDonk
BFix Locked and Loaded
BFix Locked and Loaded
Posts: 2756
Joined: Sun Jul 27, 2003 7:53 pm
Location: San Jose, CA
Contact:

Re: 1976 Bronco Brakes

Post by DirtDonk » Wed Jun 03, 2015 12:17 am

mhowsmon wrote:1) Is there any difference in size of brakes lines from front than rear for?
Usually on the fitting sizes are different. For all intents and purposes, the line sizes are the same.

mhowsmon wrote:2) MC - should front brakes hook up to front valve or rear?
At least for our Fords, the front brake lines are ALWAYS to the rear port.
As are most vehicles.

mhowsmon wrote:3) Bore size, what is the recommended size? I have heard smaller is better braking?
Almost no such thing as a consistent "is better" as it depends on the circumstances and what you're trying to achieve.
A larger bore will move more fluid, and is appropriate for power assist and larger brakes (i.e. large calipers and such) but a smaller bore will allow your foot to impart more "power" through the pedal because it has to move less fluid. But that fluid has to do some work, so there is a compromise. Too small and you don't move enough fluid. Too large and you have to push down too hard to get it to do anything.
I think all EB's were something like 7/8" maybe? Dont' trust my memory though on that. Wait for someone to confirm.

mhowsmon wrote:4) Power brakes, assume the vacuum of off of booster provides this? How far should tube from brake peddle push in the MC?
Correct as far as the engine vacuum goes. Not sure what your other question is though. What tube, and are you talking about with, or without power assist?
Assuming your '76 had the factory power brakes (most did, but manual was still available I believe) the pedal rod does not directly contact the master cylinder.
The pedal rod connects to the cantilever mechanism in the angle bracket, which pushes the booster diaphragm, which in turn pushes the booster rod into the back of the master cylinder's piston.

What are you referring to when you say "how far"?

mhowsmon wrote:My symptoms are that after bleeding brakes, I can get the drums working pretty well but I am not getting enough brake line pressure the ever engage the disc brakes (brand new calipers). I have bench bled MC, checked and re-checked for leaks. Any advice for good known setup would be greatly appreciated.
Your proportioning valve could be bad. Or a hose collapsed maybe?
Are you pulling out on the little nipple thingy (delay valve) on the prop valve when you're bleeding the front?
The prop valve is the little distribution block thingy mounted to a bracket on the frame just below the master cylinder. It's what the soft lines from the master plumb into first.
Pulling the delay valve while bleeding is not always needed, but if you're having trouble you should do it just to rule it out.
Besides, if it's sticking it could block fluid flow to the front brakes.

Good luck.

paul
'71 Bronco - 302 4v
3.5" WH/Skyjacker Lift
33 x 11.50 x15 Thornbirds on 15x7 Enkei's
Kayline soft top
Hanson bumpers
Dual batteries, Large 1G alt.

WWW.WILDHORSES4X4.COM :mrgreen:

mhowsmon
Bfix "What's a Bronco?"
Bfix "What's a Bronco?"
Posts: 2
Joined: Tue Jun 02, 2015 7:31 pm
Location: Amarillo, TX

RE:

Post by mhowsmon » Wed Jun 03, 2015 3:28 am

2) Rear port is closest to firewall correct?
3) The bore size comes out of what exactly? The bore size to the lines coming out of MC?
4) I am referring to the end result, how far booster rod gets pushed back into the cylinder piston (thanks for help with terminology). The rod seems sort of short to engage MC fully but I'm sure if you go to far you will blow ring or something.
5) I did get a new prop valve so I think it is good. Pulling out on the nipple is something I have not tried but will.

Thanks for help!
Mike H
1976 Bronco

Post Reply