Disc Brake Conversion Failing

The car is 67, I did a 68 disc brake conversion up front. the brakes were stopping but not locking and really doesn't feel much different from drum/drum application and the pedal does feel pressure

  1. How did the car stop before the conversion?
  2. Are the front calipers Kelsey Hayes, 4 piston?
  3. We're the calipers rebuilt?
  4. How long have you been driving a manual brake car?
  5. Did you do the propper brake in of the pads / shoes?

I replaced the drum/drum MC with a disc/drum MC

I think we have established that the MC is a DRUM / DRUM. The drum / drum MC has a residual check valve in both ports. If there is one in the port you have attached to the front discs you might be dragging the front brakes heating them up causing them to glaze or just plain overheat.

also replaced the stock distribution valve for what I think would be the correct proprtioning valve

If you got a complete 68 system you will have the distribution / safety switch and a proportioning valve. No metering valve.

In the 67 thru 70 something KH system, the distribution block for disc or drum is the same. Down stream in the single line to the rear brakes is a separate proportioning valve. It takes the line pressure from (just numbers for example) 1000 psi and reduces it to 300 psi. That way the braking force for the front is in line with the rear. Otherwise the rear would lock up way before the fronts and you would be switching ends when you try to stop.

Welp after all of this only one wheel is locking and it happens to a rear one at that

The adjustment of the rear shoes could explain this. Or shoes not broken in propperly, the backing plates could have worn spots where the shoes ride causing them to stick. Air in the system, Lots of reasons.

Pleeeeaaase help. MC was bench bleed, no air in the system (I've bleed and bleed the system) new shoes in the rear, new pads up front, new everything and no locking

Locking up is not the benchmark you should be looking at.

When the wheels lock they are sliding and it takes longer to stop, plus you loose control.

You want the brakes to not lockup but stop the car in the shortest distance.

There is a lot going on here and a lot of good advice. as someone already said the braking system is a system. Take it one step at a time.

I know they are corney but watch this video

Good luck.