Topic: Which GT Master Cylinder?

[MWM]

I have two different large single bowel brake master cylinders.  One of the MC's has just one brake line on the front, the other has two brake line fittings (one at a 45 pointing down).  Which bowel is correct for an early San Jose fastback with disc brakes?  Also, what is the difference between the two MC's and when were they used?
thank you!

[CharlesTurner]

First, no such thing as a GT master cylinder since disc brakes were a standalone option, although required on 65-66 GT's.

The answer to the question is that there should be 2 ports on the master cylinder.  Also consider that '65 typically are the style without flared inserts, so a brass insert with a flare is required.  Was changed for '66.

Have no idea what the single port version was used for.  Most likely an earlier Ford?

[jwc66k]

I thought that the disc brake master cylinder was originally used on a T-bird. That may explain a single port. However, my San Jose May build 65 GT Fastback has no adapter fittings on the brake lines, but my San Jose Oct build 66 GT Fastback has adapter fittings. The 66 is "relatively" unrestored.
Remember, for 65-66 disc brakes, the front port is for the rear brakes, the lower port goes to the distribution block for the front brakes.
Jim

[Bob Gaines]

Any service replacement stock after 1966 production started would most like be the flared type MC with any of the unflared type being used up in short order. With that said a out of sequence usage like a flared type MC on a May of 1965 car would most likely be a replacement at sometime by a PO. I think there is a later transition date in the MPC on the flared vs unflared MC part. Even a original owner might not remember a detail like that which could have happened almost 48 years ago. Just my thoughts . Bob

[jwc66k]

My 66 GT Fastback has the original master cylinder, not a replacement. The previous two owners stated that the brakes, except the pads and rear shoes, were not replaced. It may be that Ford was using what was available. I cannot answer for the 65 master cylinder as it's history is unknown.
The only changes documented in the Ford Car Parts manual was the transistion to a fixed push rod on 1/3/66.
Jim

[Bob Gaines]

My 66 GT Fastback has the original master cylinder, not a replacement. The previous two owners stated that the brakes, except the pads and rear shoes, were not replaced. It may be that Ford was using what was available. I cannot answer for the 65 master cylinder as it's history is unknown.
The only changes documented in the Ford Car Parts manual was the transistion to a fixed push rod on 1/3/66.
Jim

Your 66 GT fastback MC is consistent to what would be expected. The 66 was not ever a issue. The 65 MC with a integral flared fitting on a May 1965 built car however is out of the ordinary and it's MC is most likely is a replacement in my opinion and was the point of my post. Bob

[mgmradio]

Both of my June 65, Dearborn cars have the early master cylinder on them.

[mts]

I have two different large single bowel brake master cylinders.  One of the MC's has just one brake line on the front, the other has two brake line fittings (one at a 45 pointing down).  Which bowel is correct for an early San Jose fastback with disc brakes?  Also, what is the difference between the two MC's and when were they used?
thank you!

The disc-brake '65/'66 Mustangs and T-Birds and the base model '65/'66 Corvettes with 4-wheel disc brakes used near identical MC's except the Corvette MC had just the single port, like you are describing. 

[MWM]

After reading your post, I did some more reading on Kelsey Hayes.  Interesting what all they built!
Thanks!

[C5ZZKGT]

Guys, Is there any correlation between the Mustang Disc m/c and the one used on the '66 7 Litre Galaxies execpt the Galaxie is power??

[jwc66k]

It's difficult to tell from the Ford Car Parts book, but 65-66 full size Fords use the 65-66 Mustang master cylinder for power brakes as a service part and 66 Mustangs used 66 full size Ford's after 1/3/66. No direct cross reference for what you seek.
However, the 65-66 Mustang disc brake master cylinder repair kit has a T-Bird part number and is also used on full size Fords, and the replacement cap for full size Fords, T-Birds and Mustangs is a T-Bird part number as well. The service kit supports only 7/8inch, and the magic date seems to be 1/3/66 when Mustang switched to a 15/16inch bore.
Jim 

[C5ZZKGT]

OK, Jim Thanks!!  Someday down the road a bit I'm going to try & put a stock/original '65-'66 Mustang power booster including brackets WITH the DISC M/C on mine just for fun, I've seen something like this done and its pretty close though.