73 disc brake install on 68 Dart

[zhandfull]

Just about finished mounted calipers in rear and had some brake lines made up.

Now I need a 73 disc/drum master cylinder and no one has one in stock. Thinking about one off a 1983 Diplomat everything looks the same bore and port size. Just need an adapter to mount on firewall. My concern is the original on the dart has that retaining clip that bolts to the master keeping the rod in. Not sure if that is needed or required for the diplomat master cylinder. See pictures on original and Diplomat style master. Will the rod be long enough after the adapter is installed?

 

[Jim Lusk]

I think the adapter needs an adjustable rod. I haven't used the late master on a disc swap so I'm not too sure what retains the rod. You can pull the residual valve out of you drum master and use it. I'm surprised you can't find the 73 master in stock in SoCal. Did you try any other year disc masters?

 

[zhandfull]

No I just called the local napa and autozone warehouse stores and asked for a 73 disc/drum master cylinder. Might have to order online from rockauto.

Never pulled out the residual valve, but now that you mentioned it aren't they just inside where the brake line plumbs in to the master. Might have to look in to that and see if the bore matches the disc/drum master.

Thanks

 

[Jim Lusk]

Yep, that's the location (or so I've read).

 

[jaws]

Get the adapter, and go with the Dippy, Grand Fury master. That's what I did on my Barracuda, and just use the old rod.

 

[abodyjoe]

I think the adapter needs an adjustable rod.

the newer 2 bolt master cyl. has a shallower push rod bore so the stock 73 style rod will work with the 2 bolt cyl and adapter.



oh and the newer master cyl. have a rubber bushing on the end of the rod that keeps it in the master cyl. the 73 an 83 will use it.

 

[abodyjoe]

here is the rubber. i know bill at RMS sells them..

 

[Rbob]

I did not want to spend a bunch so I cut mine in half, run a 7/16-14 die and bought an allthread coupler and 2 jamb nuts for about 3.00 from Tacoma Screw.

I measured before the cut and made it 3/8" longer.

Now the only thing I am unsure of is do I put the little rubber into the master cylinder 1st and then push the rod in?

 

[Rbob]

Well damn, I have been reading lots of posts about the adjustable pushrod before I cut my brake rod this morning and after reading this post again, abodyjoe stated:
"the newer 2 bolt master cyl. has a shallower push rod bore so the stock 73 style rod will work with the 2 bolt cyl and adapter."

So I go measure my old m/c and the new one with the adaptor installed and it is the same depth with the adapter installed. The last pic the tape is even with the adapter, just bad camera angle.

It appears that you can just use the old one. Good thing I have an Adjustable Brake Rod now!

 

[green1]

Just get a piece of vacuum tubing; use it as the rubber at the end.

 

[zhandfull]

Well damn, I have been reading lots of posts about the adjustable pushrod before I cut my brake rod this morning and after reading this post again, abodyjoe stated:
"the newer 2 bolt master cyl. has a shallower push rod bore so the stock 73 style rod will work with the 2 bolt cyl and adapter."

So I go measure my old m/c and the new one with the adaptor installed and it is the same depth with the adapter installed. The last pic the tape is even with the adapter, just bad camera angle.

It appears that you can just use the old one. Good thing I have an Adjustable Brake Rod now!

Thats nice to know. I ended up just ordering a original 73 style master because I didn't want to spend a extra $100.00 on adapter and adjustable rod. I really like the looks of the newer style like you have much better.