[sweetk30]

first thing those load valves love to go bad and freeze up . by pass it .

then looking up the 87 burb master cylinder part #'s .

11" rear brakes was aluminum / plastic tank master with small bore size .

13" rear brakes was cast iron master with bigger bore for more fluid flow .

so if bypassing and bleading the rear dosnt help the next step is bigger master to match the bigger rear brakes .

but also double check the brakes are adjusted in the rear . self adjusters dont do crap most of the time . jack up the rear so tires are off the ground and click them up till just starting to scuff the drum face .