Hello  Members   After a struggle to get new master cylinder I did. I put new copper gaskets (from NAPA) on both junction blocks (one on MC other on frame below MC. Both seeped a little. After staring at problem it appears new gaskets OD is a little larger than the little recessed area with machined groves where junction block bolts thru. This recess part is about .012 deeper(total) than flat part of block. Thinking gaskets are riding on the flat area will not allow gaskets to crush. Looks like both (1/2" on MC and 3/8" on frame} are special size both OD and ID. Fords books says MC gaskets are .70 OD X .51 ID. Will try to reduce OD but ID is still oversized the might not allow gasket to center. Any advice

i had the same problem, purchase two new copper gaskets from c&g ford parts in san diego problem solved.

thanks for reply.  Problem with frame junction block it is only 1/2 inch wide  at sealing surface with a little over 3/8 bolt hole in it.  Replacement gaskets  ID are 25/64" doesn't leave much sealing surface. I believe original gaskets ID was a few thousands over .375 instead of .390.  Anybody have original specs?  Had to reduce OD down also. May have leak stopped  but only by less than  1/16" of  sealing surface each side of block.

Am I the only one who is having a problem figuring out what they are talking about?............not sure why a hole for a mounting bolt would have a gasket (what I call a crush washer).
The only brake junction block (that I can remember) with a dual purpose mounting hole is the one on the differential housing that is a breather also.

Rich, I am with you on this. The junction blocks on my car have flared fittings.

Lynn

The og single circuit m/c has a brass fitting, or 'junction block' if you will, held by a hollow bolt that accepts the stop light switch. there are copper gasket rings between the flat surfaces of the brass block.
Like og poster mentioned, these tend to seap, when using modern replacement copper rings, that don't have the exact dimensions. been there done that...

OK, now I understand. Thanks Gunter!

Thanks for comments.  Follow line down in picture in post above, to where it meets left wheel cylinder hose. That the junction block Iam  having trouble with. . Don't know how to pictures up.

This help?

Quote from: mustang6984 on 2026-03-03 09:48This help?

mustang6984, what is that thingy coming off of the valve cover stud?

It's a vintage top oiler kit. The oil passages to the rocker shafts are very narrow and can get clogged with old oil sludge. (there is a Z bend in the head gasket area). An easy remedy on oil starvation in the top end (squeaky rocker arms) was plumbing down to the oil pressure switch (idiot light sender), with an adjustable valve.
Those kits can still be found NORS online.

I used this, because my og engine had a lot of sludge and I wasn't able to clean out the passages without disassembling the engine.

What G said. In the original design oiling of the top rockers was less than stellar. So there were a lot of options for "fixing" the issue.
My rebuilt 312 has better oiling now than original, and according to the machinist who did the work I'll not need an assist.

Leaking brake line fitting....


Lynn

Thanks Lynn. Still weeping a little, used a longer box end wrench on bolt, fear stripping bolt or treads in brake hose.

have you tried annealing the copper rings ?

Often the new copper rings are way to hard to settle correctly. You could possibly use aluminium rings.