Alum drums holding boost

[MSDGN]

On my 87 GN which is a street/show car only...I used to be able to hold 4-5 PSI boost on the brake...I recently swapped out the iron drums for aluminum ones(to help with frame clearance for the Nittos)...now I can't hold any boost...wheels start spinning as soon as any boost comes on...I'm suspecting since the drums had been turned and I used the old shoes that the drums just need time to seat with the shoes...the shoes are adjusted pretty tight...does this sound logical or is there a problem with alum drums holding boost?

 

[rastaz]

Do you have the big brake cylinders? Are you still running a Powermaster? I would change the rear shoes anyways as they're not that expensive.

I run aluminum drums with the big cylinders and I can hold 15 lbs with the powermaster system.

 

[MSDGN]

Nope don't have the big shoes/cylinders...really don't care as this isn't a race car but since you state you can hold boost with the alum drums I'll stick to my theory that the old shoes just need to seat to the new drums...guess time will tell...

 

[rastaz]

FYI, I couldn't hold more that 2lbs of boost without the bigger cylinders. This is back when I ran steel drums too.

 

[MSDGN]

Really?...on my 87 T(race car) I can hold 8-10 PSI with stock cylinders/shoes...iron drums and the drums have nice grooves in them...