1971 Master cylinder replacement

This isn't a build thread or anything, just a lesson learned on replacement master cylinders for the dual circuit MC in '71's and I suppose the other Dauntless years.

My MC started getting soft last week, I checked the front calipers and the rear wheel cylinders, bled the whole system, no change. So I looked around at the FLAPS, Advance auto parts, O'Reillys, etc. They all listed part no. 10-1292 as the standard replacement. I could see in there stock photos they were selling the same rebuild MC under there own house brand names, but they all used the same stock photo.

It was obvious from the pics the cylinder was different from the original Wagner which I still had installed. But I Figured for $26 I could get one and everything would work fine.

But, as you can see by the photo below there are quite a few differences that would require a new plunger/push rod at additional cost because the new one had a deep pocket for the push rod to go in. Also it will need new brake lines because the fittings were different size. Then I would have a non-stock rigged up master cylinder, probably spending $50 more than the cylinder on the required parts.

So my solution was: I bought an exact reproduction replacement MC for the Wagner from Crown for $111, free shipping. I bought through an ebay store, east coast jeeps. The extra cash will be worth it. I won't have to buy a bunch of extra parts to make it fit and it should be (hopefully) as solid as the original set up. I realize it is probably a Chinese repop unit, but the rebuilds from the Flaps were made in China too.

http://www.crownautomotive.net/product/J0945556.html

Old MC is on the left. I brightened up the top photo to show the .470 dia X 1.00 deep cavity in the new MC that prevents it from working with the old push rod.

 

I had the same issue with my 1970 recently. As recommended by some on this site, I sent mine to White Post Restorations in Virginia and they installed brass sleeves and completely rebuilt it. It is more expensive than the Crown but so far it has worked perfectly. Would be interested to know how the Crown unit works out.

 

I'll update this thread when I get it installed. Probably about 2 weeks.

 

yep they are the place for vintage/classic car restorations
White Post Restorations in Virginia

 

Is this the place?
http://www.whitepost.com/

 

Yes

 

The new MC arrived today from crown. The casting has a few minor differences, but overall looks good. Maybe this weekend I'll squeeze some time it to change it, but Probable next weekend.

 

Have you opened up the new Crown unit to see if it has a stepped bore like the original Wagner Lockheed?

Don

 

Focker: Yes, it has the Residual pressure valve, I removed the front one as you can see here. It is similar to the Wagner RPV, but not exactly the same.

Don: no I did not open the main part of the MC, I did not want to screw something up before I used it.

I got the new MC installed Friday evening and took it around a few miles, seems to be working fine. Very solid. One thing I did not like: the manufacturer did not do a good job of tightening all the fittings. The drain plug was just little more than finger tight, the port adapters need a little snugging down too.

 

Focker, (and anybody else interested in this) I have opened up one of these Crown MC and looked at the bore size. It has a straight 1" bore for both pistons, not the stepped bore size of the original Wagner MC. This ought to work fine depending on the size of the wheel cylinders. The original stepped bore would put higher fluid pressure on the front brake wheel cylinders to prevent rear wheel lockup.
Many of us have upgraded to 11" brakes all the way around, with a smaller bore wheel cylinder in the rear brakes. The Crown unit should work fine in that application. I haven't tried yet to see if it will push enough fluid for a front disc application.
Don