One thing no one has mentioned. Bronze valve guides have pluses and minuses. One BIG minus to me (and it's why I don't use them) is that they CANNOT run dry even for one second. If they do, you get the result you had. They MUST be lubrcated properly upon assembly. If they are not, kiss them goodbye. I much prefer a good old iron or steel guide over bronze. They can take more abuse and they generally last longer. Of course, they are more expensive to replace.