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-   -   Problem with '74 'Vette master cylinder (http://www.hotrodders.com/forum/problem-74-vette-master-cylinder-199625.html)

hduff 06-01-2011 04:45 PM

Problem with '74 'Vette master cylinder
 
The master brake cylinder on my ride leaks, so I figured it was time to replace it. It's the classic '74 'Vette master cylinder. (the casting number on the body is 29969).

So I went to NAPA, got a reman m/c (with casting number 29969), but it's notteh same part.

The cup where it receives the rod from the vacuum booster is shallow, whereas the replacement part is deep. The other m/c's that NAPA has have a deep cup.

Is this a power/manual brake difference? Am I confused? Is NAPA confused?

Henry the 32nd 06-01-2011 07:14 PM

A master from a 74 Corvette won't work because it would have been disc disc. All corvette's 65 and later are 4 wheel disc, however in 65 they had a 4 wheel drum brake option,giving you money back. If yours has a top like the Corvette perhaps it is from a Camaro?

hduff 06-01-2011 08:54 PM

Quote:

Originally Posted by Henry the 32nd
A master from a 74 Corvette won't work because it would have been disc disc.

I have 4-wheel disc brakes. The leaky m/c is a '74 'Vette.

Sorry I wasn't clear.
My problem is the business end of the m/c.

There's a depression or cup where the pushrod from the brake booster pushes against it.

The "correct" m/c has a shallow depression; the one NAPA keeps trying to give me is about an inch deeper. they say it's the same part, but obviously it's not.

Bryan59EC 06-02-2011 07:13 AM

The deep bore is generally for manual brakes

The shallow bore is for power brakes only.

You can purchase an extension rod that will replace the one currently in your booster, or, sometimes there is a plug available for the deep bore that changes it to a shallow bore.

I bought parts froom Classic Performance products to deal with this on a couple of my vehicles-----but the plug seems to only want to work with the masters that they sell.

KUHL46 06-02-2011 09:44 AM

NAPA Master cyl
 
NAPA numbers may be wrong. I had a similar situation last week. I was looking for a manual master cyl for a Vette. According to their computer they brought in one that had the shallow piston hole for a power booster.
I got the right one from Advance Auto Parts. Their listing was correct

hduff 06-02-2011 02:13 PM

Thanks guys. Now that I have an idea of what is wrong at NAPA, I can get things straight.

artsvettes 06-04-2011 09:00 PM

68-76 corvette master cyl were the same. They changed in 77-82 along with the brake booster. There is a diffrence between manual and power brake master cyl

hduff 06-04-2011 10:17 PM

Quote:

Originally Posted by artsvettes
68-76 corvette master cyl were the same. They changed in 77-82 along with the brake booster. There is a diffrence between manual and power brake master cyl


All of the m/c sthey had in stock were manual and incorrectly identified as power brake m/cs. The new master cylinders were correct.

cobalt327 06-05-2011 07:18 AM

Quote:

Originally Posted by hduff
All of the m/c sthey had in stock were manual and incorrectly identified as power brake m/cs. The new master cylinders were correct.

Just goes to show you that "defensive parts buying" has to be done even at NAPA, who's considered by many to be a cut above the others. :smash:

artsvettes 06-05-2011 09:20 AM

New meaning to NARA know how"

T-bucket23 06-05-2011 04:52 PM

The casting number means nothing in this case as both a manual and power brake MC would have the same casting number. Only one of the internal parts is different.


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