They are a stop gap, but quality kit and ive used them often in heads that were a bit tired of having the guides often removed, split guide bosses happen after all, i also found they suck oil, probably down the join line, this may not be a problem on some uses, i had a blue smoke puff every time i came out a of corner on the circuit cars that used them.
Hmm. thatīs weired I/we have use "tons" of them in anything from Harleys to ACVW to V8 engines. I have never experienced oil consumption, yet. The K-lines are stronger than normal guides used in the AC world. I.e. they last longer than a regular guide replacement.
I tend to think that the blue smoke was caused by the rings doing overtime rather than the guides. If it was the guides, the blue smoke should be almost all the time and not just out of corners.
T