rear disc brake question

[74calicharger]

i was wondering if anyone can tell me if converting to rear discs changes how far out the rear wheels are pushed or is it the same distance as drums. And do i need to change the master cylinder and distribution block. my car is a 74 with front discs and rear drums on an 8 3/4.

[John_Kunkel]

Since the axle flange is in the same position for discs/drums the only difference is in the thickness of the drum and the disc hat; the disc hat is usually a little thicker than the drum, probably 1/4" or so depending on who makes the disc so the overall width of the rear end would be 1/2" or so wider.

A '74 with front discs would have a combination valve that proportions the rear drums, whether or not it would work correctly with rear discs depends on the type of rear caliper. The residual pressure valve in the front port of the factory master cylinder would need to be removed when used with rear discs.

[74calicharger]

thank you for your response. everyone on this site is very helpful and i appreciate and thank all of you