Brake conversion help

[rattleon]

I changed my '70 from all drum power assist, to disc up front w/ original drums out back. I changed out the prop. valve and using original booster. My question is can I still use the original duel res. master cylinder or do I have to change it out also? Is there a volume problem with the original? Thanks for any help.

[Hottrucks]

subscribed I'm going to be doing this swap this winter

[oldblue1968chevy]

if you had drums 67-70 and went to disc 71-72 you need a 71-72 MC

[dwcsr]

The after market MFG's say you can use the original, But some originals have a residual valve in them and would make the front brakes hang. I would go with the 72 master to be sure. They only cost about $18 plus core.

[smn69]

I made the same change and the MC for Disc/Drum have larger resivors to handle the extra volume needed for the front disc. I would go witht the 71-72 MC.

[michael bustamante]

good question. I didnt know about this

[70 Suburban]

i used my 72 m/c but its still a 50/50

[smn69]

Originally Posted by 70 Suburban

i used my 72 m/c but its still a 50/50

Yes they are 50/50, but just bigger than the drum/drum MC

[70 Suburban]

I wouldnt know. I used it in a 65 chevy.. they have a single port.

[cparman]

I agree with old blue chevy. You need a disc drum master cyl

[Hottrucks]

nice to see we all agree...it's 50/50?????

[70 Suburban]

Ha

[rattleon]

Thanks for the input. It sounds like a volume thing more than anything else, so I'm going to play it safe and install a 71-72 m/c. $14.95 plus core and it's in stock at the local parts house. When it comes to brakes...that's cheap piece of mind, but damn!! that m/c top polished up so purrrdy!!!