Problem with brake swap.

inertia said

I think you should first verify that the front calipers aren't seized, as that was a common problem with the "plastic" pistoned calipers.

Jack the front wheels off the ground, apply brakes and see if a wheel can be turned by hand. Spin a wheel and apply brakes and see if the front brakes will stop the wheel, then try the other side.

If the brakes will not apply and stop the wheel, with the brake pedal still applied, crack open a bleeder on either side to see if there is fluid pressure at the caliper.

If there is pressure at the calipers that won't apply and stop the wheels, the caliper is likely seized, and needs replacement.

Click to expand...

As above... if you have NO front brakes, then you have problems up front. No prop valve in the world will fix that.

If you don't get any pressure at the bleeders, then the rubber lines to the calipers may be plugged. When they get old, the inside liner falls apart and plugs them up internally; the front brakes then either don't work, or they lock on and never release.

The 67 MC was for a drum/drum setup, but should work the front calipers OK, BUT this MC has what is called residual pressure valves in each output, front and rear. These are designed to make sure the fluid does not back out of the wheel cylinders of drum brakes. This needs to be removed/punched out from the rear MC chambers outlet, which feed the new front disc brakes. Otherwise, they will tend to hold the front brakes on lightly all the time.

Another issue with the 67 MC will be as the pads wear out; the back cylinder of the 67 MC (which feeds the front brakes, will not have enough fluid capacity to avoid running out of fluid as the pads wear and the fluid drops. You will have to add brake fluid as the pads wear, and then remove it when you put new pads in. Putting in a 73-76 MC will avoid that.

With the front A-body brakes, and 11" rears, you will need to put in a prop valve eventually to get the rears to not be too strong. And BTW, the prop valve does not increase front pressure; it reduces rear pressure.