Sorry it took so long to reply, but I wanted to make sure of what I thought I remembered. 65fastbackretro, I don't think your problems are with the MC. Your symptoms (soft pedal, next to the floor) sound like this:
Quoting from
http://www.thebrakeman.com/valvetechi ,
"We may as well start with the residual valve, because it is the first one that should be determined whether or not it is needed. This valve does exactly as its name suggests. It keeps a pre-determined amount of residual pressure in the line after you remove your foot from the brake pedal. This aids in preventing excessive pedal travel as well as insuring consistent height to the pedal. In a drum brake, heavy return springs are present to pull the shoes away from the drums. When not in use, the shoes are pulled back until they rest on a centering pin, usually located at the 12:00, or top position, on the backing plate also holding the wheel cylinder. In order to avoid the excessive pedal travel to move enough fluid from the master to activate the shoes, a 10-12 pound residual valve is installed in the line. Sine the return springs are stronger than the 12 pound valve, the shoes are pulled away from the drum in spite of the resistance so no brake drag results."
Contrary to what ultrastang said, the residual Pressure valve is
not in the port of the MC I got from Napa.
Here's some pics I took of the port and valve from an old '67 Mustang MC I had sitting around, and the port and seat from the Granada MC I got from NAPA. You'll see the lack of a valve:
http://s266.photobucket.com/albums/ii272/d_harrelson/respressure%20valve/
I couldn't find anythin definitive about the Ford combination valve speciffically, but the consensus sure seems to be that the residual pressure, proportioning, and metering functions are all included in the combination valve.
Again quoting The Brakeman:
"To really get the most practical benefit from this information, you first need to know what valves are in your system, and where they are located. The residual valve, for example, could be found in a variety of locations. On most American cars and trucks up to the mid 1960's, the valve will probably be found inside the master cylinder. In a single master cylinder, it will be located at the bottom of the bore and look like a little brimmed hat. In a tandem master, it will be in one or both outlet ports and look like a brass seat. On most all American and foreign newer cars, the residual valve is usually incorporated with other valves in a "combination" valve. (More about the other valves later). This combination valve can be located on a stock vehicle by simply following the line out of the master cylinder until you arrive at a junction block. This block usually has two lines going in from the master and two lines going out, one to the front brakes and one to the rear brakes. Most commonly, the combination valve is found on the firewall, within a foot of the master, just beneath the master, or on the left frame rail near the lower "A" arm"
65fastbackretro, as I understand your last post, you've plumbed your new MC directly to the original '65 distrubution block (a simple 4-way "Tee"). By doing this you've negated the benefit of the dual system and MC, because both sides of the MC are now tied together, and with the new MC, you've totally eliminated the residual pressure valve that the drums need to overcome the return springs, hence the long pedal travel.
For a comprehensive view of the R.P.Valve, read:
http://books.google.com/books?id=5rW-ppyB_ugC&pg=PA71&lpg=PA71&dq=residual+pressure+valve&source=web&ots=fbkAdjnzmq&sig=eEKiXNOgUikY_ND9qkHNCNFORoc&hl=en#PPA70,M1. Although this article doesn't mention the comb valve, it's still a good description, and describes more about why they were eventually phased out, but it doesn't say anything about overcoming the return springs.
http://www.hot-rod.com.au/builder/brakes.html says (among other things):
"Residual Pressure Valves are used in a both front and rear brake system as follows:
2 PSI Valves - These valves are used in a disc brake system only and are required when the master cylinder is at, or below, the height of the calipers. It's purpose is to act as an anti-siphon valve preventing the brake fluid from siphoning back into the master cylinder when the brake pedal is released. Even if the master cylinder is even or slightly above the calipers, put one in anyway. If you don't and you park on a hill, fluid will siphon! These valves are cheap insurance - put them in! NOTE: You will know if you need one of these valves if you had to pump the pedal twice to get a good pedal. See illustration for more.
10 PSI Valves - These valves are used in a drum brake system to prevent air from being ingested into the hydraulic system when you release the brake pedal. Typical wheel cylinder seals only seal when there is pressure behind them. Rapid release of the brake pedal creates a vacuum in the system which causes the seals to relax and air is ingested into the wheel cylinders. Maintaining 10 PSI in the system at all times prevents this. Some disc/drum master cylinders have 10 PSI residual pressure valves installed internally, some don't. If you're not sure, call us and we can tell you how to check. Also, some new style wheel cylinders have cup expanders which negate the need for the residual pressure valve. Either way, if you are not sure whether you have one or not, put one in. They are not cumulative and it won't hurt anything if you have two. Don't worry about brake drag, it takes roughly 75 PSI to overcome the return springs"
So I guess the bottom line is that ultrastang is right about the use of residual pressure valves because of the mc being lower than the wheel cylinders, but there is more to it than that.
I haven't touched on the other functions of the comb valve, but with a disc drum system you need a metering valve to apply pressure to the rear brakes first, and a protioning valve to adjust the bias from front to rear. Read about the combination valve at
http://auto.howstuffworks.com/master-brake2.htm.
I know I've rambled all over in this post, but it's pretty complicated.
I made my Granada brakes work by using a Granada MC & a Granada (or equal) comb valve. They worked very well without any other valving. There is plenty of good info in the links above if you want to learn more.
Sorry for the lengthy post.
Later,
Dennis
He needs some valves before he goes any further.
If it doesn't solve it, you're gonna have to look deeper, and why spend money if you're gonna change something.
