Master Cylinder Gift Horse

[ursus]

I need to replace my 1940 Ford master cylinder and a friend offered to give me a new one from a Hudson of the same era. It has the same 3-hole mounting flange and overall length as the Ford MC. My friend is convinced it can be used in a Ford, but I'm not so sure. Any thoughts about such a switch?

[RalphM]

I don’t see why it wouldn’t work. When I built my first truck a 1945 commercial i used a master cylinder off of a military trailer from the 60s.

[skidmarks]

Clark forklifts used the same master cylinder. Just check the bore size

[Terry,OH]

Same diameter? If so should be good to go. I believe Dia. is marked on the side of the MC.

[Mart]

Master Cyl diameter needs to be 1-1/16".

Mart.

[revkev6]

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I bought a master cylinder off Ebay years ago that claimed it was a 39 Ford unit or a Hudson unit. When I got it the mount pattern is correct but the shape isnt ford. Looks like it may say 1" on it?

[revkev6]

Here's a pic of the casting number on mine

[revkev6]

just did a litter research, based on the casting number the master cylinder I have is for a forklift and costs about $18. it's 1" bore. really, if it works it may be a cheap option for a master cylinder.... hudson has a master that is listed on ebay for 46-47 pickups that is similar looking to this unit which also has a 1" bore.



thoughts?? given the pain in doing the brakes twice I may just put this one on the shelf and spend the $40 on the correct master.

[JSeery]

The small diameter mc will decrease the foot force required on the pedal for the same braking force at the wheels, but it will also increase the pedal travel. With a single chamber mc don't think that would matter much as long as the pedal travel is acceptable.

[revkev6]

Originally Posted by JSeery

The small diameter mc will decrease the foot force required on the pedal for the same braking force at the wheels, but it will also increase the pedal travel. With a single chamber mc don't think that would matter much as long as the pedal travel is acceptable.

currently I have the same brake setup with a 39 style master in my 28 roadster. I have the brakes adjusted a little tight atm.... i get about an inch of pedal travel before it hits like a brick.



that makes me wonder if I could use the 1" but I get concerned about the stroke and such...

[modeleh]

Originally Posted by JSeery

The small diameter mc will decrease the foot force required on the pedal for the same braking force at the wheels, but it will also increase the pedal travel. With a single chamber mc don't think that would matter much as long as the pedal travel is acceptable.

A smaller piston will result in more input effort.

[tubman]

Originally Posted by modeleh

A smaller piston will result in more input effort.

I don't think so. The smaller the diameter, the less fluid has to be moved per a given amount of pedal travel. Less fluid moved, the less the effort. Your only worry is running out of pedal travel. Imagine a master 1/8" in diameter; you'll have to have a lot of travel to move the same amount of fluid as one 1" in diameter, but it sure would be easy to push.

[JSeery]

Originally Posted by modeleh

A smaller piston will result in more input effort.

Nope, smaller diameter, less foot pressure and more line pressure, but increased pedal travel.

[modeleh]

Disregard

[ursus]

The MC in revkev6's photo resembles the one I was considering. Interesting comment by JSeery regarding the effect of using one with a reduced the bore size - it makes sense from my limited experience with hydraulic stuff. I was hoping somebody with experience using the Hudson MC in a 39-48 Ford might comment here.

[Frank Miller]

There will just be a bit more travel before the shoes tighten up on the drums. Like a hydraulic jack, once it has pressure on it every movement is exerting pressure. I wonder if hudson wheel cylinders are the same diameter as Ford? If so you're just copying their engineering.