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Upgrading B Body Power drum brakes.

Azmotorhead

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Jun 8, 2024
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Location
Peoria AZ
I'm in the process of upgrading the power drum brakes on a 70 GTX. Putting Discs up front. Leaving the 11"drums in the rear.
I can't seem to find a definitive answer to"Do I need a new master cyl and Prop valve?.None of the brake conversion packages that are being sold come with a master or prop valve. Some old threads here and other boards say yes you end to change the master. Probably a good idea as I dont think the original master has a residual valve in the front circuit. It would be too easy to call Pirate Jack or another vendor but alas its the weekend.
 
You will probably need a dual-diaphragm booster and larger bore master cylinder. You may need a different proportioning valve or an adjustable valve in the rear circuit. In my experience a lot of heartache could be on the way.
 
Thanks CKessel. Good article with valuable info. I'll have to check the booster to see if its a dual diaphragm or single.
 
I'm in the process of upgrading the power drum brakes on a 70 GTX. Putting Discs up front. Leaving the 11"drums in the rear.
I can't seem to find a definitive answer to"Do I need a new master cyl and Prop valve?.None of the brake conversion packages that are being sold come with a master or prop valve. Some old threads here and other boards say yes you end to change the master. Probably a good idea as I dont think the original master has a residual valve in the front circuit. It would be too easy to call Pirate Jack or another vendor but alas its the weekend.
Your factory booster is a 9" single. If engine vac is good it will be fine. Just change the master to the disc/drum master for your car RAYBESTOS MC36283
 
Since you're in Zoney land, you may have access to many of those needed items at wrecking yards. DVAP maybe or others.
 
Thanks it's been a decade or two since I hit DVAP.
Last time I went Mr Hoctor wanted gold for a few pieces of tin.
 
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