Topic: 1966 GT Master Cylinder replacement?

[jameslgleason]

Hi all, I?m restoring my ?66 GT coupe and a previous owner replaced the master cylinder with a dual bowl. I?d love to go back to the single bowl, but mine is a June build and all of the MC?s I?ve seen for sale are pre 1/3/66. Do you know of any place to source a new/refurb unit? It?s not a daily driver and the rear brakes/lines are brand new, so I?m not worried about failure.

[jwc66k]

I think the difference is that after 1/3/66, the push rod had a retaining clip to keep it in place. Pre and after 1/3/66 have the same piston 15/16 inch piston diameter. The biggest problem may be in finding a three port distribution block.
Jim

[Bob Gaines]

Hi all, I?m restoring my ?66 GT coupe and a previous owner replaced the master cylinder with a dual bowl. I?d love to go back to the single bowl, but mine is a June build and all of the MC?s I?ve seen for sale are pre 1/3/66. Do you know of any place to source a new/refurb unit? It?s not a daily driver and the rear brakes/lines are brand new, so I?m not worried about failure.

The typical single circuit/bowl disc brake master replacement looks identical for all practical purposes. The early style you mention had brass adapter fittings to go from the pipe thread of the bowl to the flared ends of the brake lines . The later 66 style like you are looking for is the only thing that is available new. If you simply have to have original then look for a core with the flared seats in the fitting holes and a "B" for Bendix on the bottom side .There will be a Julian date code also if that is important to you. If the used core is the route you are going then you are in luck because the later 66 style is the most common out there. Expect to pay about 250.00 for a rebuild on a original core. It doesn't make good financial sense to rebuild a pretty exact looking replacement given they are only 68.00 new. https://www.npdlink.com/product/master-cylinder-assy-brake/103652

[jameslgleason]

Thank you! Is there a trick to knowing which proportioning valve works?

I?m not so worried about perfect authenticity, but at least getting in the ballpark. It?s not a show car?yet!

You guys are awesome!

[OldGuy]

Thank you! Is there a trick to knowing which proportioning valve works?

I?m not so worried about perfect authenticity, but at least getting in the ballpark. It?s not a show car?yet!

You guys are awesome!

What type of proportioning valve does your car currently have? It should have a Kelsey Hayes cast iron unit (with a large adjusting screw extending forward) bolted to the inner fender panel below the master cylinder. Both the Ford-supplied assembly line and the service part replacement units look virtually identical with the exception of the top surface detail (where the fittings attach).

Frank

Frank

[Bob Gaines]

If there is no sign of leaking then that is a good sign that it "may" be good. There are not other visible tells on the outside. If it has never been rebuilt after 5 decades or so then more then likely it needs to be. I send mine off to a rebuilder to have it sleeved and rebuilt. There are rebuild kits readily available but if the bore is pitted then you have to have it sleeved.I error on the side of caution and assume the bore will be pitted.

[Scott302]

Jim,
3 port blocks are easy! 2B075-1A
https://www.npdlink.com/product/distribution-block-disc-brake/148101?backurl=search%2Fproducts%3Fsearch_terms%3D2b075-1a%26top_parent%3D200001%26year%3D
Regards,
Scott

I think the difference is that after 1/3/66, the push rod had a retaining clip to keep it in place. Pre and after 1/3/66 have the same piston 15/16 inch piston diameter. The biggest problem may be in finding a three port distribution block.
Jim

[jwc66k]

Scott,
NPD does it again.
Jim

[jwc66k]

Thank you! Is there a trick to knowing which proportioning valve works?

The proportioning valve looks like this (file photos). It is adjustable, and the instructions are on this forum somewhere. It's made by Kelsy-Hayes so it's on cars other than Mustangs.
Jim