rear drum to disc conversion...have factory front disc

[djais1801]

Considering changing the rears from drum to disc. Do I need to change anything under the hood...booster/master cylinder-if I have discs up front?

 

[Chryco Psycho]

Yes , drum brakes require & 10 lb residual pressure valve , disc do not , so if you want to use the same master you need to remove the flare seat , brass insert where the brake line out attaches by inserting a drywall screw & pulling out the insert , behind that there is a rubber 1 way cheack valve that needs to be removed , re-install the seat & you can use the same master . The bias will be off with the factory proportioning valve so I would also install the wilwood 5 port adjustable prop valve to balance the front & rear brakes .
i would probably install a newer alum master with a shared reservoir so you do not run low on fluid in the reservoir for the rear brakes but you still need to remove the residual P valve if the master had drum rear brakes .

 

[djais1801]

thanks!!