Low Pedal After Adding Dual Master Cylinder

[430bird60]

I added a dual master cylinder to my 1960 with the Kelsey Hayes booster and now I have a very low pedal. It stops as well as before. I have a friend with a 60 that has the booster under the hood and his car also has a low pedal after changing to a dual master cylinder. I'm wondering if adjusting my under dash booster will give me more pedal? I do have self adjusting brakes. Any information will be greatly appreciated. Thanks.
Ken

[jopizz]

You should be able to adjust the push rod eccentric adjusting lever under the dash to lengthen the push rod. If that doesn't work you may need to use a longer push rod. Refer to the diagram.

John

59 brakes.jpg

[430bird60]

Thanks John. I forgot about the pushrod. I bet that is the problem, but, I will try the adjustment first. Thanks

Ken

[simplyconnected]

Ken, for your friend with the booster, he needs to adjust the jack screw/jam nut on the OUTPUT side of his booster. Follow the procedure in your Ford Shop Manual. If someone presses the brake pedal, that jack screw comes out far enough to put a wrench on the nut. (We had one member who bought a longer jack screw at his local hardware store because the one that came with his booster was too short.) People assume that new components are the exact same dimensions as the originals.but it ain't necessarily so.

I adjusted mine using a small square of American cheese, still in the wrapper. Some folks used Play-Doh or clay. Before the pedal is depressed, you want the booster's jack screw to push on the master cylinder's piston ever so slightly. Too much and the piston won't return and the brakes will never bleed back to the master. You can look down the master's reservoir and see the small hole where the piston travels making fluid goes in and out. If the piston is closing that hole, fluid cannot return.

For this job, none of the hydraulic lines need to be disconnected, only the master-to-booster bolts need to be removed. No special tools need to be purchased. - Dave

[430bird60]

HI Dave. Thanks for the information about the under hood adjustment. I'll pass it on to my friend. I haven't had a chance to adjust mine yet. Thanks again.

Ken

[simplyconnected]

You're certainly welcome, Ken. - Dave

[cuul59]

I hope you found these suggestions useful. What I am curious about is what brand/model dual master were you able to add? When I added a dual master to my ‘59, I pulled out the under dash KH unit and replaced it with an underhood mounted booster. It works very well and I would have liked to keep the KH but at the time I couldn’t find a dual master that would fit and work.

[simplyconnected]

There is a lot more room under the hood for the kind of booster you need. The bellows type next to the brake pedal does not offer much boost. Ford abandoned that type as well, in favor of a firewall mounted booster.

The original firewall mounted booster was a single stage ten-inch booster, barely large enough for drum brakes but certainly too small for front disk brakes.
Adding front disk brakes is by far the best upgrade you can do for your car. I've never heard anyone say they will go back to drums. I suggest all Squarebird owners install a dual-piston 1" bore master cylinder with a two-stage 9" booster. This combination is perfect for front disk brakes. - Dave

[430bird60]

Hi CUUL59. My car has the Lincoln 430 engine with Kelsey Hayes booster under the dash. I installed a dual master cylinder for a 67 Mustang, The only issue is that it has two mounting holes instead of four which has not been a problem. When I installed it I failed to measure the depth b/t the mounting surface and the plunger for the pushrod. Apparently I need a longer pushrod as my pedal is not far from the floor. Their is an adjustment but I haven't had a chance to make it.

Ken