hot rear brakes

My 66 barracuda has a rear brake problem, I converted to front disc,
the car has an 8.75 rear axle 10" brakes new shoes, hardware, drums.
The rear manual proportioning valve is set wide open, you drive the car and
the rear pass side drum is scorching hot, enough that it toasted a set of shoes the drivers side seams to be normal temp and the front discs are also normal temp ? I have tried resetting
adjustments, doublr checked everything including the emergency brake adj and setting,
what am I missing.