Master cylinder replacement snafu - help

[CW4B]

Decided to replace 1/4” brake lines between MC & distro block. Couldn’t find prefab line with correct fittings for one of the connections, between the rear MC fitting (nearest vacuum booster) and distro block. So I searched around and found a “dual MC adapter” that, after everything connected and brake pressed, the “adapter” leaked like a siv(sp).
See pic. Sorry, puc didn’t work.
Evidently wrong adapter but that was the only one that would even screw into MC that also accepted the tub fitting.
Any suggestions?
Adapter = AGS BLF-25C 9/16-18
Prefab brake line = 7/16-24 to 1/2-20

[HO455]

A quick look up of the fitting you listed shows the female end as inverted flare but the male end as "straight". I believe it should be a male inverted flare.

https://www.rvautoparts.com/BLF-25C-..._p_299027.html

Is the leak from the male end?
Does the female part on the distribution block have a cone shape in the bottom of it like the first photo?
If so then the fitting you need will look like the second photo and third photos.
You have the correct thread pitches but the wrong style of fitting. Thank GM for making it that way so drunk UAW employees wouldn't screw it up on the assembly line.

[CW4B]

That’s it, I’m sure. What do I say I want to the clerk? Or what do I search for? These darn fitting sizes and numbers of threads and inverted vs straight has me going crazy.

[HO455]

The big end should to be 9/16-18 male inverted flare and the small end to be a 7/16-24 female inverted flare. To make it more confusing 7/16-24 inverted flare is commonly called a 1/4" brake line fitting. The link below may help.


https://agscompany.com/product/brass...6-18-inverted/