Dual master cylinder f100 brakes
 

Using a dual master cylinder with f100 drum brake front and rear.

Master cylinder is a 1" bore from a AMC product.

Of the 2 ports, which is front and which is rear or does it matter?

With this style master cylinder, are inline residual valves needed?

Re: Dual master cylinder f100 brakes
 

When I installed a drum/drum AMC master cylinder on my Merc. years ago the master cyl. had the residual valves built in and no others were required.

Re: Dual master cylinder f100 brakes
 

A word of caution: A dual master cyl. conversion such as this may not work as intended! If pressure is lost front or rear, the pedal will go nearly to the floor before the remaining brakes engage. If total pedal travel is anything less than the OEM application, you will lose all braking and probably crash!
Save your neck and your car by testing your setup. When everything is hooked up and bled, you likely will have good brakes with little pedal travel. But now, open a front bleeder screw and try a panic stop. If the rear wheels don't slide and the pedal goes all the way to the floor, the system failed. Time to re-engineer! Repeat on the rear brakes and the fronts must lock up or again, fail.

Re: Dual master cylinder f100 brakes
 

That’s interesting ....
You think your adding a safety factor in you car and you’re creating a hazard...
A friend had that very thing happen on his old Willy’s pick up...
I’ll show him this post ...
Your learn something new here,,thanks for your input..
Carl...

Re: Dual master cylinder f100 brakes
 

I put a dual master on my 34.
The important question is what diameter master are you taking out.
If the diameter is smaller it will take more pedal travel to push the same a mount of fluid to stop the car so diameter is a big fact.
Second I put residual valves is both lines at the master to hold the fluid on the wheel cylinders so the pedal is always firm.
Third the hole closest to the mounting flange is internally valves for the front brakes
Good Luck

Re: Dual master cylinder f100 brakes
 

Is this on all dual master cylinders or disc./drum (larger resivor for the disc)?

The one I got is for drum/drum

Re: Dual master cylinder f100 brakes
 

Is this on all dual master cylinders or for disc/ drum (larger resivor for the disc) ?

The one I got is for drum/drum.

Re: Dual master cylinder f100 brakes
 

It doesn’t matter what the master was made for it matters what the piston diameter is.
Different cars and trucks used different diameter wheel cylinders .
If your new master was bigger than what you took out that would be ok , but if the diameter is smaller the pedal will have to go down further to stop the car


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Re: Dual master cylinder f100 brakes
 

The larger resivor is for disc brakes because there pistons are bigger and need more fluid

Re: Dual master cylinder f100 brakes
 

The dual master is a wise upgrade, but it has to be able to full stroke before the pedal bottoms out for it to provide the added safety, something many still don't fully understand. :)

Re: Dual master cylinder f100 brakes
 

Yes I understand that,

The question was, the port closest to the mounting flange goes to.the front brakes on all dual master cylinders for both drum/drum or drum/disc

Re: Dual master cylinder f100 brakes
 

All drum/drum masters are not 50/50 in operation, so knowing the correct primary/secondary or front/rear plumbing is important. The port (hole) closest to the mounting flange is NOT always intended for the fronts.

Re: Dual master cylinder f100 brakes
 

Yes the first piston is the primary piston for the front brakes whether disc or drum.

John

Re: Dual master cylinder f100 brakes
 

Well with the last two post,
Anyone know which port on a 1970 AMC drum drum master cylinder goes to the front brakes?

Re: Dual master cylinder f100 brakes
 

NO, NOT always. Bad information.

Re: Dual master cylinder f100 brakes
 

Yes, seem to recall that there are two springs in the piston assembly and the weak spring side is the one that goes to the front, which activates the fronts first and when the fronts are pressurized the second (strong} spring collapses to activate the rears.

Re: Dual master cylinder f100 brakes
 

It is usually the front port to the front brakes, but I would check with a brake shop or find a diagram on line for that cylinder. On a disk/drum master cylinder there is a large and small area for the fluid--large is for the disk brakes. This large area is in the front of the cylinder. On a drum/drum cylinder both areas for fluid are the same size. I used a '67 mustang drum/drum cylinder on my 39--worked OK. I think the AMC cylinder is the same except the ports are on the opposite side.

Re: Dual master cylinder f100 brakes
 

Need to know too, using a '70 Javelin master in my 32 chassis. Their disk/drum master has the large reservoir closest to the booster. May not apply for drum/drum.

Re: Dual master cylinder f100 brakes
 

Here is a '67 amc vehicle which clearly shows the port near firewall is being used for the front line; split for left and right.

Re: Dual master cylinder f100 brakes
 

That's a pretty cool master cylinder with the brake lamp switch in the bottom. Would come in handy for later swaps too that used the same switch.