Just My Opinion: I would install it. Worst Case Scenerio:The circlip or piston go rogue(you have a leak) on your master cylinder and brake fluid squirts everything under your dash! Never has happened to me, but it seems like that may help prevent it.

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1964 Dart GT

I guess I could just install the flange, spring, boot and retainer with no screws holding the flange to the MC and it would be loose and pull away from the MC back every time. This is poor planning: I'm surprised at Raybestos.

I'm also surprised my MC didn't come with this rubber interlocking piece since you all are telling me I need one. What the heck??

That stock early boot won't work on the later master cylinder, you need one from a late car (like a '73'-76 Valiant), they have a different size and attachment. The mid-A cars (1967-up) sometimes have a plastic/nylon plate that the rubber boot goes into then bolts behind the master cylinder using the 4 studs on the firewall (typically these are cracked and disintegrated by the time you replace the cylinder in an original car).

FYI.

-D.Idiot

Hmm. I may drill and tap new holes in the MC to be able to use the old retaining flange and boot. Waiting around to get a new boot setup at this moment is not an option.

Got the rod out. Needed leverage. The bench vise and a hammer prying did the trick. Hope I can re-use that rubber piece - looks a little worn, but with luck it will pop back in and stay there.

Another thing - I'm noticing that on my old setup, the brake line from the MC to the junction block is bigger than 3/16". The fittings fit correctly the but pipe is bigger. Are the lines going from the MC to the junction block supposed to be 3/16" or bigger?

Don't reuse the rubber locking piece. Get a new one. Stall the job if you have to. These aren't available at parts stores separately unless you can convince someone to go through a bunch of MC boxes until they find one. You can buy them from www.doctordiff.com or a few other mopar places.

If the circlip or piston "go rogue" you'd have other problems to worry about besides a leak. Mainly how your going to stop the car. This is a dust boot to prevent any debris from getting into the cylinder bore when the piston is depressed. My 71 had the plate DI was talking about sandwiched between the firewall and MC. This plate had a ridge on it that extends into the cabin. An accordion style rubber boot fit over this ridge and the other end onto the rod. The plate was fine but boot was history. Didn't even bother

The lines - any mopar I've seen was 3/16". How certain are you they are 1/4" ? Then again I haven't fussed with single pot stuff. If it really is bigger then you'll need new nuts and lines. Heads up - front port is a mopar only oddball thread 20tpi

Everything has been put back together. Thanks for the guidance to those who offered some. Yet all is not well in the land of Oz.

Bench bled the MC before installing it, then proceeded to bleed the brakes. Made sure the chambers were full of fluid and kept checking to keep them full throughout the process. Started bleeding the rears, then the fronts, all in sequence as standard.

Ended up with a very spongy-feeling brake pedal that definitely doesn't define "high and hard". Should I expect spongy with the dual chamber MC or high and hard as per usual?

I think either I didn't bleed all the air from the lines, or I managed to suck air back into the lines through the bleeders because I didn't close them all the way before my passenger lifted the brake pedal.

Is there any differences I need to observe when bleeding a dual chamber master cylinder as compared to the single-pot?

High and hard for a manual. Power as well if engine's off. Does the pedal get any higher or harder when you pump it a few times in rapid succession?

I'm a fan of pressure bleeding. For bench bleeding - start with an empty reservoir and push fluid through the ports back into the master with a large syringe. Can bleed a unit quickly and more foolproof.

high and hard is what you are going for. someone is probably gonna say oh no thats not how you do it but ill let you know how i bleed a master cylinder anyway. bolt it on the firewall and put something under it to catch the fluid coming out. have someone pump the pedal slowly and use your fingers on the ports as check valves. you will know when its good. keep good pressure with your fingers on the ports. when they pump up you should be able to tell when the air is gone, it will come out in a smooth stream. if you keep good pressure on there you will feel the air. once the front or back start pushing with good pressure like its supposed with no bubbles, hook that line up and continue pumping till the other comes around. ive used this method a few dozen times. the only time it didnt work the master cylinder was defective. it works and its fast. it is also messy. you could do it on a bench and save your paint in case you cant catch the fluid coming out. when i was younger i used those lines that come with the new mc but that takes for ever and doesnt work as well. as far as bleeding the rest of the system when using a new mc i like to start with the mc move to the back brakes, mc then the front.

Thanks, both of you.

All the bleeding was done again yesterday. Stopped some leaks and the pedal is better now, but still not where it needs to be.

Realized the issues now are mechanical with my recent brake job. Posting about that separately now.