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Master cylinder piston hold in tab concerns

Started by Soflocudaguy, December 21, 2024, 05:24:55 PM

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Soflocudaguy

I Have a 70 cuda manual Drum brake car, I purchased reman MC . Is the small flimsy metal tab With one screw the only thing that holds the piston in ? What applications were the oval plate with 2 bolts used ? I see several old MC'S laying around a buddy's shop and some have the oval plate and some don't. Any Breakdown of when and what should be used is much appreciated.

pschlosser

I, too, am curious which models the 2-screw diamond-shaped retaining plate was used.

Keep in mind, the flimsy 1-screw retainer is just fine.  There is very little (if any) force ever pulling on the piston to pull it from the M/C.  The retainer just needs to be strong enough to counter the force of the piston return spring within the unit.

JH27N0B

For manual brake applications it's a retainer for the dust boot.
Not used when installed on a power booster.


pschlosser

Quote from: JH27N0B on December 21, 2024, 09:15:49 PMFor manual brake applications it's a retainer for the dust boot.
Not used when installed on a power booster.

Good call.  I think it's the same boot, be it on the back of the booster, or back of the master cylinder.  But that retainer may be manual-only drum brake master cylinder.   The dealer parts book  suggests the master cylinder (for front drum brake) was  the same for both manual and power.

JH27N0B

The master cylinder was the same either way.  You'd reuse the boot retainer installed on the old master cylinder, along with the pushrod, if you were servicing a manual brake car.
A new rubber pushrod retainer was supplied with new master cylinders to use to install and secure the pushrod in the master cylinders primary piston, which mechanics working on a power brake car would just discard.
They may have even included a new boot?
The rebuild kits had new boots included I'm pretty sure.  I probably have a NOS kit stashed away which I'll have to dig out and look at.

cuda hunter

"All riches begin as a state of mind and you have complete control of your mind"  -- B. Lee

Soflocudaguy

Dorman m71258. It did not come with anything. I never had an old set up to go by.
I have the correct rod with new rubber grommet. The piston did have the groove inside to hold the rod/grommett in place. I'm just trying to figure out if the Tab is all that really holds the piston in correctly/safely. Dorman shows it for manual Brake and a 1 inch Bore which shows correct for 70 E manual drum set up.


pschlosser

Quote from: Soflocudaguy on December 22, 2024, 12:26:36 PMDorman m71258. It did not come with anything. I never had an old set up to go by.
I have the correct rod with new rubber grommet. The piston did have the groove inside to hold the rod/grommett in place. I'm just trying to figure out if the Tab is all that really holds the piston in correctly/safely. Dorman shows it for manual Brake and a 1 inch Bore which shows correct for 70 E manual drum set up.

I have the same problem.  No boot retainer.  I'm hoping when I find a used one, it will come with  the retainer.  "The Ram Man" has used ones for sale at $35 a pop.