[USMUCL]

I also wondered if it could be the GM nuts . . . or perhaps a combination, i.e. "tolerance stack."

Interesting that mine wouldn't even cleanly thread. That said, since the seal is made by the line flares being pressed against "crush" points in the new lines, I still theorize that imperfect threading has your flairs not mating flush.

Regardless, I'm not willing to try again. This was always just a bonus while I had the front calipers off for vented pistons. Plus, the GM crush washers are very specific and the track fluid expensive. I don't feel like chasing my tail.

I'm already having nightmares about the new pistons leaking, LOL.