Question regarding the port on a brake booster

Not quite tractor-related but the Chevy C60 in question is a farm truck that hauls grain that is grown with the help of a tractor . . .

The brake booster on my FIL's 1975 C60 went out so we ordered a numbers-matching replacement from a name-brand auto parts store. Everything on the new booster was a direct fit except for one hydraulic connection. The steel tube coming to the booster has a flared end with what measures to be a 1/2-24 male threaded nut. This threaded directly into the port on the old booster. However, the new booster has a port that measures at 1/2-20 and came with an adapter installed in it. Our problem is that the female thread in the adapter is too small for our existing line and I've been unable to find a suitable adapter on-line.

Anybody have any suggestions? It is the 1/2-24 thread that has me confused since this would be the pitch for a compression fitting but the appearance of the nut and tube is the same as a typical inverted flare connection. However, an inverted flare thread is 1/2-20, not -24. Although I deal with hydraulic fittings all the time at work I don't know much about these automotive-style connections so I'm curious if any of you guys have any advice.

Thanks

I suspect the inverted flare "port" was damaged and the "rebuilder" bored it out and installed the (incorrect) adapter.

A couple of years ago I installed a "rebuilt" booster and it had a similar adapter that fit the brake line but wouldn't seal to the booster itself, a close look revealed a botched threading job.

Had to return the booster for another which was OK.

Suggest you try again, as well.

The other possibility is that the rebuilder didn't have a "core" for your type of booster and used a core that was originally made to accept a "banjo fitting" at that port and made a failed attempt to adapt it to build the part number unit you require.

Either way, they failed to provide you with a functional replacement for your specific application.

I would remove the adapter and see what's there.

It's just a plain 1/2-20 threaded port
with no inner sealing surface for a flared
tube. The female end of the adapter does
have a flared sealing surface but it it's
too small for our line.

I don’t think that will work even if you get the correct adopter maybe a tapered pipe thread could seal. Not the place for a leak.

Posing as a new customer.....
I would call the vendor or have a buddy email them.
Then inquire about the port asking them what size and style of port it has on that unit. Not mentioning what size type you need.

Maybe yours was screwed up like mentioned.

Got an update on this. As it turns out the thread on the brake line was in fact a 1/2-20, not a -24 like was first thought. This made all the difference in the world as that is a common size for an inverted flare fitting. We were able to find an adapter at the local auto parts store that joined the adapter shipped with the booster with the line. Thanks to all who chimed in.