Topic: 1967 GT500 front disc, rear drum issues still

[kkupec02]

Looking for advice. Bought car a year ago with no brakes. Had master cylinder, booster and front fender apron mounted distribution block rebuilt. Got back brakes but no front disc. Had calipers rebuilt and installed with new rotors, turned, and pads. Dash brake light stayed on due to piston shift probably. Re-bled back brakes and got dash brake light to go off. Took car out. Still bad brakes. Fronts still don't seem to be catching and even rears catching less. I have a problem with getting any wheel to lock up. Got a little front left brake chatter. Anyone have a guess about the front left brake chatter/clicking or why I still have no front discs? I also have to replace rear axle mounted proportioning valve. Plumbing is correct. I have good firm high pedal when car on or off. The only thing that I can think of is a plugged shared right and left front disc line since neither side works, or a bad rebuild on the master cylinder or fender apron mounted distribution block which is centered as the dash brake light works and is not on. Front brake flex hoses were replaced by the previous owner just before I bought car so they are brand new. Maybe 100 miles on them and one year old. I have the original dual bowl master cylinder to the car for disc/drum with the original Midland booster all rebuilt professionally. 
 

 

[Bob Gaines]

Looking for advice. Bought car a year ago with no brakes. Had master cylinder, booster and front fender apron mounted distribution block rebuilt. Got back brakes but no front disc. Had calipers rebuilt and installed with new rotors, turned, and pads. Dash brake light stayed on due to piston shift probably. Re-bled back brakes and got dash brake light to go off. Took car out. Still bad brakes. Fronts still don't seem to be catching and even rears catching less. I have a problem with getting any wheel to lock up. Got a little front left brake chatter. Anyone have a guess about the front left brake chatter/clicking or why I still have no front discs? I also have to replace rear axle mounted proportioning valve. Plumbing is correct. I have good firm high pedal when car on or off. The only thing that I can think of is a plugged shared right and left front disc line since neither side works, or a bad rebuild on the master cylinder or fender apron mounted distribution block which is centered as the dash brake light works and is not on. Front brake flex hoses were replaced by the previous owner just before I bought car so they are brand new. Maybe 100 miles on them and one year old. I have the original dual bowl master cylinder to the car for disc/drum with the original Midland booster all rebuilt professionally.

Power disc master cylinder is different from a power drum master. Two different numbers. There is a long number on the bottom side of the master that will tell you what you have . Post it here .

[ruppstang]

The easy way to tell difference is that the power drum master cylinder has equal chambers, where the power disc has a large and a small chamber. 

[67gtasanjose]

Rubber hoses break down and clog up.
When this happens, you usually won't get much pressure or fluid out the bleeders. This condition also causes the brakes to be hard stopping and difficulty in releasing.

...but of course, rebuild that rear valve too.

[kkupec02]

I took these pictures before the rebuild. I guess I'll have to buy some pressure gauges. Unless the "newer" front flex lines both failed, I am at a loss.

[RoyceP]

Are the rear drums adjusted properly? Is the brake booster vent spacer in place? Is the brake booster pushrod adjusted properly? Does the person bleeding the brakes have experience performing that task and all the others above?

[67350#1242]

The MC pictured would not be the factory piece for your 67 GT500.  The factory casting number should be 2227161 and would look very similar to this reproduction:
https://www.deadnutson.com/1967-68-mustang-shelby-master-cylinder-with-cap/
The number in your picture 2227091 corresponds to a boss 429 application.  This is not to say that your brake problem is due to this, and brakes may work fine with it but you should check out the specs and compare to the correct one.  Original MC bore is 1" - am not sure about the one in your photo.
A good test for booster operation is to hold foot on brake while starting. When engine fires you should feel your foot drop toward the floor as vacuum builds.  I have had rebuilt boosters fail.
Also as mentioned make sure the length of the pushrod is adjusted correctly.
Kurt.

Edit:  The Boss 429 MC bore was 15/16" - not sure how this would affect your brakes.  Maybe some one with more experience will chime in?

[Bossbill]

I would take the lines off of the master and run the plugs and tubes that come with most rebuilt masters. These plugs and tubes will send fluid back into the bowl so you can verify that the master is operating right. That's step one.

[Bob Gaines]

I took these pictures before the rebuild. I guess I'll have to buy some pressure gauges. Unless the "newer" front flex lines both failed, I am at a loss.

The picture is of a much later service replacement master. The correct number for a Bendix master cylinder used on 67-70 Mustang/Shelby disc brake is  2227161 .The numbers in your picture are hard to read but don't look like all the correct digits. The Boss 429 master is 2227091 which looks more like the picture but I can't tell for sure. FYI to answer the question before it is asked given that it is a replacement master cylinder that doesn't look like the assemblyline unit if it is the same BOSS 429 number I suspect it would not have any desirability over what a typical aftermarket generic core would have.

[kkupec02]

Thanks all. It looks like I have a lot more to do, but not sure where to start other than going through the whole system. It is a Boss 429 master cylinder number. I wonder what it is worth if I am better off selling it and replacing it. I just had it rebuilt.

[Bossbill]

Thanks all. It looks like I have a lot more to do, but not sure where to start other than going through the whole system. It is a Boss 429 master cylinder number. I wonder what it is worth if I am better off selling it and replacing it. I just had it rebuilt.

By starting at the master?

[Bob Gaines]

Thanks all. It looks like I have a lot more to do, but not sure where to start other than going through the whole system. It is a Boss 429 master cylinder number. I wonder what it is worth if I am better off selling it and replacing it. I just had it rebuilt.

I supposed you missed the part of my post where I answered your question before you asked it. "FYI to answer the question before it is asked given that it is a replacement master cylinder that doesn't look like the assemblyline unit if it is the same BOSS 429 number I suspect it would not have any desirability over what a typical aftermarket generic core would have."

[kkupec02]

I got what you said. I was wondering if I should sell the Boss 429 master and buy an original master that would match the car.

[kkupec02]

ie, sell the Boss 2227091 that I have and use the money to buy a 1967 Shelby 2227161

[Bob Gaines]

ie, sell the Boss 2227091 that I have and use the money to buy a 1967 Shelby 2227161

If you can get anything for it would be found money IMO. People typical ignore aftermarket or service replacement ones like in your picture.The ones that are desirable are like assemblyline.  After market or later service replacements like yours are typically only have value as a core (15.00?) when buying a over the counter rebuilt replacement. Given it is the wrong application for your car I am not sure what kind of effect it has on your brake system. It may have something to do with your problem or may be not. It only makes good sense to have the correct master on your car while trying to diagnose a problem like your describe you are having .