Spongy Brakes

[JSeery]

I don't know about shoebox brakes, but F1 are Bendix brakes, not Lockheed.

[Mart]

Adjust the rear brakes up solidly so there is no movement and see if that makes a difference.
As this is a non stock application it is up to you to work out what is going on.

What is the pedal ratio? What is the master cylinder travel at 6" of pedal travel?

Is the pedal push rod adjusted so there is no free play movement there?

Is there any dead movement before the piston travels past the recuperation port? This travel needs to be at a minimum.

Are the front and rear brakes from the same vehicle? What is the master cylinder diameter for this vehicle.

It might be that you need smaller rear brake cylinders.

For instance 50 ford cylinders are .875. Yours are 1".

It's hard to advise when it is a non stock application. You have to make sure all the relationships between cylinder diameters and lever lengths all balance and the best way to assure that is to mimic a stock application.

Mart.

[JSeery]

"Cylinders are a 48-51 Ford 1 1/8" and 1" on the front and 1" on the rear."

OK, something is not right here, are you using Bendix brakes or Lockheed brakes? These are Bendix brake parts, I think. Bendix brakes do not use two different sized cylinder bores on the same cylinder. Now I am totally confused with what you have going on. Do you have a photo of the brakes?

Which of this does your brakes look like?

[gvgehrig]

Problem solved. Thanks to all those that offered help. It's been like learning how a magic trick is done -- "that's so simple, why was it so hard to solve." The short answer is that the shoes were not properly adjusted. I find it difficult to believe the very, very, very, small adjustments on the cams translates into such a large pedal movement, but I guess it does. I think Mart hit it correctly. The MC is too small. The pedal is about 12" and the rod pushing in the MC piston is about 5". The MC is 1" trying to displace two 1" wheel cylinders and to 1 1/8" wheel cylinders. So I guess a few thousands on each shoe is a really big deal. In the for what it's worth area, the MC is below all wheel cylinders and I have no pressure valves installed. I plan to add them at a later date just to see how much difference they make. Thanks again to all.

[tubman]

I would seriously consider getting the proper-sized master cylinder. It sounds like the one you have provides very little margin of error. If a very small change in adjustment makes the difference between adequate and marginal brakes, any little failure anywhere could leave you with out them.

[JSeery]

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Not overly important at this point, but you might want to correct what the wheel cylinders are just for future reference, believe they are not 48-51. Sounds like you have the Lockheed brakes.