Upgrading B Body Power drum brakes.

[Azmotorhead]

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.

 

[gdrill]

Yes and yes

 

[yella71]

and yes

 

[ckessel]

This article should be of great benefit to you.
Disc-O-Tech

 

[Mackman]

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.

 

[Azmotorhead]

Thanks CKessel. Good article with valuable info. I'll have to check the booster to see if its a dual diaphragm or single.

 

[MIKESPOLARA]

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

 

[ckessel]

Since you're in Zoney land, you may have access to many of those needed items at wrecking yards. DVAP maybe or others.

 

[Azmotorhead]

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.

 

[ckessel]

I bet. Any other more reasonable sources around?