Ford disc conversion, master cylinder?

[bad 68]

wich master cylinder is prefered for the Ford disc conversion? 76-77 Bronco or 76-79 F150? They have different part numbers, but do they have a different bore size?

 

[shamu]

Call Wild Horses. They have the big bore M/C that works like no others. And tell Nik I sent yah.

 

[DirtDonk]

You're shameless Hopper. ;D
You still gettin' yer monthly checks?

You can actually use either of those bad 68. Or one of ours.
And yes, the two are different bore sizes usually. The EB masters were supposedly all the same size, while the full-size had a slightly larger piston. Depending on applications, the full-size could range between 1" and 1.25" if I remember. Ours is 1.125 (1 1/8") for reference.
Personally, I would not go larger than 1 1/8 if you have manual brakes. You can go larger if you have power, but it's not mandatory.

The EB master you referred to would also have the fittings on the passenger side and be different sizes than your existing master. Not sure if the full-size, whether for power or manual brakes, would have them on the same side you do now, or if they're opposite.
The ones we sell have ports on both sides of the master cylinder and come with some adapter fittings so that you can fit "most" existing rigs.

You can also use your existing master cylinder until you get the one you want. Gives you more time to decide just which way to go. Which can be a good thing with so many choices.
Do you already have the brake parts? If so, you can install them even before you get the new master. I like ours because of the just slightly larger bore AND the dual-sided port layout. They also have equal sized reservoirs which makes them more compatible down the road with rear disc brakes. Should you decide to go that route later.

Paul

 

[DirtDonk]

Oh, and are you planning/using power brakes? Or keeping them manual?

Paul

 

[bad 68]

I have power brake booster allready, Drum front, 11x2.25 rear drums. I may go rear disc eventually as in the parts loft is sitting a 75 big bearing Torino rear housing. But for now I just plan on doing what donk sugested. Installing the discs knuckles out and trying out the master with the stock prop valve and see what happens.

And one more thing, I am installing the Tbird calipers so that may effect the master choice. But to me it doesn't make sence to go with bigger wheel calipers and bigger master bore just to offset each other. But I may be wrong. It would be the first time though!

This isn't a hypothetical upgrade. I have all the parts. Should have the front axle housing back together tomorrow night and drivable by friday.

 

[DirtDonk]

And one more thing, I am installing the Tbird calipers so that may effect the master choice. But to me it doesn't make sence to go with bigger wheel calipers and bigger master bore just to offset each other. But I may be wrong. It would be the first time though!

In this case, the larger bore master is called for because of the larger piston calipers.
It actually IS appropriate to offset one with the other. The larger the piston of the caliper, the larger volume of fluid it takes to move it a given amount and still apply a reasonable amount of force against it.
Keeping your stock master will still work, but a larger bore in the master cylinder will ultimately give you a firmer pedal. ( edit: ) Firmer, but you have to apply more leg/foot pressure to achieve the same fluid pressure against the caliper piston.

If you like the way it works out, then you're good to go. If you have a soft mushy pedal though, and you know you got all the air out because you bled it thirty three times, and then twice more for good measure, then it's time for a larger piston.

Remember to look for a residual pressure check valve in the output port of the master cylinder that feeds the front brakes. Leaving it in "might" cause the front brakes to drag.
Taking it out at least guarantees that it won't.

The stock valve is not actually a proportioning valve. It's merely an "H-block" assembly to house the switch for the Brake Warning Lamp on the dash.
Here again, using your existing one is fine, but do some brake testing while driving to make sure that the rear brakes don't lock up prematurely. If they do, then you have to swap out the H-block for a real proportioning valve. Either stock type, or adjustable.

Paul

 

[bad 68]

Thanks for the help Paul. 10-4 on the H block. I knew that, just called it by the wrong name. Who is "WE"? I'm not familiar with who you work with.

 

[shamu]

Thanks for the help Paul. 10-4 on the H block. I knew that, just called it by the wrong name. Who is "WE"? I'm not familiar with who you work with.

Paul works for Wild Horses.