[Pops @ Tri-5.com]

Need to replace the M/C on my newly acquired '55....It is leaking and is actually the wrong one.....The car has drum brakes front and rear....Could order this M/C: http://www.classicchevy.com/chevy-dual-brake-master-cylinder-with-power-drum-brakes-1955-1972.html But don't want to wait for it to be shipped.

What replacement should I ask for at the parts counter? The Nova and Chevelle carry the same part # However, the Belair/Impala is different....Both M/C have a 1" bore with 1/2"X20 and 9/16"X18 outlets...So, I should imagine it makes no difference....Any advice would be most welcome.

 

[Rick_L]

What year for those cars are you looking at? Obviously anything 55-66 is going to be a single reservoir/single piston unit.

67-68 Chevelle/Nova/Camaro should be the same and should be good for your application. Not sure why the Impala wouldn't be either.

I'm assuming from your other posts that this is a no booster deal for drum brakes.

A drum brake m/c for the above cars should have residual valves but some rebuilds don't have them. You need them if it's drum brakes.

All 67-68 Chevelle/Nova/Camaro master cylinders should also have the deep cup for the pushrod, whether they are power or not.

 

[Pops @ Tri-5.com]

Rick...I'm looking at replacing the M/C on this booster: See link: http://www.trifive.com/forums/showthread.php?t=48833 with a 1970 power brake M/C for front and rear drum brakes.

If I need to go to a different booster I can....Also, I'm not sure what size bore that I should be looking at....The M/C for this application that East Coast Chevy sells is 1 1/8" bore....The ones I've been looking at are 1" bore :confused0006:

 

[Rick_L]

Several questions here.

You almost certainly have a shallow cup master cylinder. But I don't know.

What is the master cylinder bore now and does it work OK?

What you have is probably 1-1/8" bore.

 

[Pops @ Tri-5.com]

Rick....I will have to get back to you on some of your questions.....I need to get the car back to the house, where I can take it apart to examine things.

When I first got the car, it had good pedal but pulled severely to the left upon brake application...I took apart the front brakes and found that the PO had the primary and secondary shoes reversed....Also, the bearings were totally over greased....Which contaminated the shoes.

Now the car stops straight (if pumped), but bleeds down to the floor.....The complete brake system (front and rear), except for the M/C and booster has been totally redone....New shoes, wheel cylinders, hoses, and drums turned or replaced...Adjusted and bled the brakes as per the Shop Manual.

Today, when taking a photo of the M/C, I noticed that it was leaking on to the booster.

 

[Pops @ Tri-5.com]

Anyone know what size bore is right fo a car with power brakes and drums in both the front/rear? 1 inch or 1 1/8 inch :confused0006:

 

[Rick_L]

One inch.

Trouble is I don't know what model might have had a shallow cup m/c.

 

[Pops @ Tri-5.com]

One inch....Trouble is I don't know what model might have had a shallow cup m/c.

Is a shallow cup needed to match this booster or necessary for some other reason? :confused0006:

 

[Rick_L]

To match your booster.

 

[Pops @ Tri-5.com]

I believe I understand what you are talking about now.....The cup is the hole where the rod goes.....This is a photo of what Don think's is there:

Here is a photo of the 1" bore 1970 belair M/C:

To me they look like they are different....Could possibly take the cup from the old and transfer it to the new, if that's the only difference.....I have another booster (72 Nova) that I can use, if I have to.

 

[Rick_L]

The photos clearly show a shallow cup in the upper one and a deep cup in the lower one.

But who knows if the photos are of the product you would get? Generic photos are often used.

The problem you have is that drum brakes usually need the 1" bore. You might try the 1-1/8" bore m/c and see how it goes.

I'm sure there's a power brake (shallow cup) m/c out there that's 1" bore but I don't have a clue what the application would be.

 

[Pops @ Tri-5.com]

Rick....I was probably editing my post, while you typed yours....

As I understand it, the one inch bore will give me more stopping power than the one and an eighth.

Could I possibly take the part with the cup from the old and transfer it to the new, if that's the only difference?.....Also, I have another booster (72 Nova) that I can use, if I have to.

 

[Rick_L]

No, the cup is part of the piston.

CPP sells an aluinum master cylinder that has a plug for converting it from deep to shallow. But that plug won't work in a stock type master cylinder.

A 1" bore m/c will give you 27% more line pressure than a 1-1/8".

I suggest you call CPP tomorrow and see if they have what you need, or try Hotrodsusa.com (call them).

 

[Pops @ Tri-5.com]

Will do Rick.....Thanks for all your help.

 

[Pops @ Tri-5.com]

On second thought.....I think I will get a 1970 Chevelle M/C and change the booster, if necessary...Stick with all Chevy, easily obtainable, over-the counter parts.

 

[Tvia57]

No, the cup is part of the piston.

CPP sells an aluinum master cylinder that has a plug for converting it from deep to shallow. But that plug won't work in a stock type master cylinder.

A 1" bore m/c will give you 27% more line pressure than a 1-1/8".

I suggest you call CPP tomorrow and see if they have what you need, or try Hotrodsusa.com (call them).


Rick,
these are all good questions and answers because I am in the precess of finishing up installing a new front disc brake system from Heidts on my 55. I have the original drums in the rear and ordered a disc/drum MC from Heidts. The MC they sent is a deep cup but they also sent me the MC plug that you talked about here. My question is am I supposed to use it? When I install the plug and the MC to the power booster it pushes against the piston on the MC before I get it tightened up. Is this correct? Or will the MC be precharged before I even step on the brake pedal? The system from Heidts also came with a rubber cup that fits between the power booster and MC is this part also needed. If you need I can load up some pic's to show you what I'm talking about. Any advise would be appreciated..!! I may need to call Heidts on Monday.
Thanks!!

TV