Brake experts, please!

I'm having a REAL tough problem with a car I'm building. I know the ins and outs of most mechanicals, but this one has been stumping me for a long time.
1934 Terraplane. Did the whole ch***is...M2 front end, Ford 9 in. Chevy motor and trans.
Power brakes is a 1-800 set-up. Corvette master and 6 in. single diaphram booster...not a lot of room underneath the car for anything larger!
Wilwood 4 piston calipers, 11in rotors, usual RPV's 2 lb. front, 10 lb. rear, adjustable prop valve installed in rear line...all lines are 3/16". Drum brakes out back.
Pedal is the original Terra part, as was most of the linkage to attach it to the booster/master. Original brakes were mechanical...this is important, as I had to both change the length of the pedal, for a better pedal ratio (now 5.5 to 0ne), and that I had to change the angle of the driven arm so it had a better angle at rest and going into the master.
Problem...the brakes just do not work well. They don't stop the car as they should. As per the techs at Wilwood, I bought a brake pressure gauge, and installed it at the L front caliper, in the bleeder (brakes have been bled repeatedly, using a power bleeder, so sir is NOT an issue) The system only develops 200 PSI, should be 800-1200, according to Wilwood. I made an adapter and checked pressures all the way up to the master and they don't change, so the RPV's and all are good. Pressure readings at the rear brake cylinders are about the same.
First thing was lengthening the pedal to get more mechanical advantage, didn't work. Originally it was only abour 3-3.5 to 1. Tried every which way to adjust and modify the linkage fro the pedal to the master, for no free play, straight shot, best angles, etc. nothing works.
Swapped out the master cyl, then made a fixture to eliminate the booster, then tried a new booster, did all these things separately, testing the system after each attempt. Nothing helped. Vacuum to booster is 16-18 in., so that's OK.
Last night tried to adjust the rod into the booster to be sure I was getting full penetration into it...made it so tight, the brakes wouldn't release when the pedal returned to rest. Still no go.
Have a bit over an inch travel AT the booster, and the pedal travels almost 6 in. up top. Does NOT hit the floorboard, so I ***ume it's going as far into the master as is possible.
Is there anything I've missed? any other diagnostic procedures I can pinpoint the problem? Is it possible that 2 new masters could be bad???????
HELP!!!!!

 

Is the pedal firm or mushy? Did you bench bleed the master cylinder? I know, you reckon you have all the air out........but I'm not convinced..........

 

chopolds,
To know for sure if you can bottom out the master, bleed off the vacuum (engine off), open both circuits (one front and one rear bleeder)and check to be sure the pedal full strokes the master before it hits the floor.

The normal power brake pedal ratio is +/- 3:1- any more and you will run out of pedal travel in most cases.

I have had bad experiences with the single 6" vacuum boosters, and in my opinion are worthless. They work fine in the very low pressure range, but "run out" or go to 1 to 1 ( manual) too early with moderate pedal efforts. Switching to a 6" tandem booster solved the problem in both systems I was involved in.

Check the booster push rod-to-master clearance-should be .040"-.050". Perform this check with the booster fully "charged", or at about 20" HG.

 

Those 6" boosters are piss-poor at best. They require you use non power ***isted brake pedal ratios. Increase your pedal ratio to 1:7 or 1:8 and your problems will be gone.

 

Thanks, guys!
I don't know if I can make the pedal any longer...I already had to make up a new pivot for the pedal, to relocate it below the top of the frame, instead of on top of the frame, so I could lengthen the pedal as much as I did. I think any higher, and it would be too high off the floor for the pedal to be comfortable, but I'll check.
Yes, I've heard some bad things about the single 6" booster. Anyone have size information on the dual diaphram 6 inchers? If they are not that much longer, one might work...cannot use anything wider, no room inside the X-member.

 

You might consider a Hydroboost or Electro boost or remote booster setup as an alternative to the 6" booster setup you have now. You can check them out at www.abspowerbrake.com

 

The dual diaphram booster is about 2 1/2" longer.

 

I ran a set up with wilwood disc up front, and factory gm drums in the back, with no booster.
I used a 1975 corvette master, would stop a 3600 lb car on a dime.

Later I put wilwood discs on the rear, not because it needed them, just to match the fronts.... and that little master handled that too. No booster.

What Im sayin is, sounds like a master problem.

 

ECI brakes offers a pressure multiplier that goes inline of the hydraulic lines. Might help your problem.

 

I don't get it.

The only thing I can think of is to pull the booster completely and manually make sure the master is making full stroke. On the bench if you have to and bleed that ****er there to make sure you are absofreakinlutely getting all the piston displacement you should.

The booster is there to ***ist only. I am talking manual mechanical movement.

After the bench test of the master is done, move it to the car and repeat, without the lines connected. Hook up that gauge to each port if you can and make sure you are getting the pressure there manually.
This will eliminate the master as an issue.

Then reinstall the booster and try it again, no lines just gauge. If it works and the clearance on the booster to master is correct, then it should soundly eliminate both.

lastly is the rod to pedal ratio.

Doing this you will find your culprit I guarantee it.

Once nailed and the pressure at each port is correct, then hook up the lines and move on down the road.

 

I have installed Brembo(similar style) brake systems a few years back. I remember a customer came in with a similar problem like yours.After a thorough inspection I found that the problem was in the front calipers.The guy installed the left caliper on the right and the right caliper on the left.The issue was that the bleeders were pointing down.He could have bled those brakes all day long and would have never got all the air out.The problem was that there was an air pocket in the upper portion of caliper that is not filling up because of the bleeders pointing downward.So while he was bleeding them.The fluid was going down straight through the bleeders.So after installing the calipers on there correct location and bled for the last time,the problem was resolved.
Willwood calipers are designed to fit many applications.Thats why they have bleeders on both ends.Depending on the set up,It can be mounted in front of rotor or in the back of rotor.
Are you bleeding the brakes from the the upper part of caliper?Also,only because it has 4 corner bleeders doesn't mean that you have go through all 4.Only the upper pair.
Check it again,Hope this info helps.
Frank