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Correct master cylinder

Sonny

It’s all fun til the rabbit gets the gun.
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I’m upgrading the front drums to disks on my ‘70 Belvedere. Not going to upgrade to power brakes. There are 2 disc/drum master cylinder bore sizes. Which one should I buy? Do both sizes use the same diameter push rod that attaches to the brake pedal?
 
The two most common sizes are 15/16 and 1 1/32 ". The small one will require less push from your leg, but will have a little more travel than the larger one. It is a personal preference, but the small one is the best bet if you don't have a big leg. Both take the drum brake pushrod, if they are machined for the retainer ring.
 
Is your old master cyl mopar?
What casting#?
and would you be interested in selling it?
Looking for a 2660009 casting #
Thanks
 
Is your old master cyl mopar?
What casting#?
and would you be interested in selling it?
Looking for a 2660009 casting #
Thanks
Nope. Napa.
 
I’m upgrading the front drums to disks on my ‘70 Belvedere.
I bought my new disc/drum MC from Napa. For your '70, should be able to tell them, you want a disc/drum manual brakes MC, and get the right one.
Be sure to get it for manual brakes, since for power brakes, it's a dif part number.

Don't know on the push rod. Mine was for my 64 conversion, and stock rod worked.
 
So, "original" doesn't matter?
I just went through this on a 67 B body.
A Diplomat master cylinder will work OK with a 1.031 bore.
(But you would need the adapter to go aluminum)
But I was unhappy with the A body disk and that master.
I would recommend upgrading to the 11.75 1978 Cordoba disk
(O'Reilly or Summit)
You would only need these if you have everything else.
https://www.doctordiff.com/disc-brake-slider-caliper-mounts-backets-for-11-3-4-rotor-upgrade.html

And this either way over the Diplomat master.
15/16 bore.
I believe that you have 1/2X20 and 9/16X20 lines?
https://www.doctordiff.com/aluminum-master-cylinder-kit.html
 
I bought my new disc/drum MC from Napa. For your '70, should be able to tell them, you want a disc/drum manual brakes MC, and get the right one.
Be sure to get it for manual brakes, since for power brakes, it's a dif part number.

Don't know on the push rod. Mine was for my 64 conversion, and stock rod worked.
That’s exactly what I did. Thanks!
 
So, "original" doesn't matter?
I just went through this on a 67 B body.
A Diplomat master cylinder will work OK with a 1.031 bore.
(But you would need the adapter to go aluminum)
But I was unhappy with the A body disk and that master.
I would recommend upgrading to the 11.75 1978 Cordoba disk
(O'Reilly or Summit)
You would only need these if you have everything else.
https://www.doctordiff.com/disc-brake-slider-caliper-mounts-backets-for-11-3-4-rotor-upgrade.html

And this either way over the Diplomat master.
15/16 bore.
I believe that you have 1/2X20 and 9/16X20 lines?
https://www.doctordiff.com/aluminum-master-cylinder-kit.html
Correct! This is a rr tribute and originality isn’t a concern. Napa is offering a $75 Visa card on all brake orders over $250, but I’m a little nervous mixing and matching brake parts. Will probably stick with a complete conversion kit.
 
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