64 T-Bolt disc brake problems

I put 4 wheel disc brakes on my 64 Fairlane T-Bolt replica and have gone thru 2 master cylinders since. I used a 67 Galaxie dual master cylinder (disc/drum). I was thinking of trying a 86 Mustang turbo SVT master cylinder as they had 4 wheel disc barkes this time. Anyone have any input or know what will work on my car? Thanks

What vehicle donated the rear axle and /or rear brake hardware?

You cannot use a disc/drum MC, the pressures for the rear are different.
A MC from a 4 wheel disc Lincoln MkV (77-79) may be a better choice. You would also need a rear disc proportioning valve, ideally from the same vehicle as the MC, or an aftermarket adjustable one.

I used a narrowed 9-1/2" from a 77 ford van, it is a big bearing housing, moser 31 spline axles, aftermarket caliper brackets, Lincoln mark 7 rotors, 80 Monte Carlo single piston front calipers. On the front, aftermarket brackets so you don't have to change spindles, 78 Granada rotors and again 80 M/C calipers. I used 80 M/C disc brake lines on all 4 corners. I will have my local parts guy order a master cylinder for a Mark 5 and compare it to the ones I have now to see if it will fit. Did you use a Mark 5 cylinder or know someone that has with good results? Thanks

So you have used the same calipers front and rear, right?
Often, rear calipers have smaller pistons, so they will exert less clamping pressure on the rotor than in front, all other factors being equal.
I think that an aftermarket adjustable proportioning valve is a great way to reduce the pressure to the rear calipers so they do not lock-up prematurely. I do not think a factory (non-adjustable) valve will work well.

As for MC's...... quite a few Lincolns in the late'70's/early '80's used 4-wheel disc systems, including the MKV, Versailles and the Fox-body Continentals (82-87). Hopefully, from those you should find something that fits.
Good luck :)

Yes, I'm using the same size calipers front and back. Does it make any difference that the master cylinders you listed that I should use, are for cars with power brake boosters and I have manual brakes?

Normally you should be using a master designed for 4w disc brakes.

Mr. Wedge, can I use any 4wdisc M/C even if it is designed fore power brakes? Nice ride

When you find the m/c you want to use, see if there is a different listing for power vs non, on some vehicles there is no difference. Rockauto.com, has good listings showing both options and piston bore size, once you know what make and model source the m/c is for.