should valves rotate ?

Ok fellas.

Why is this the first time in twenty five years of dicking with cars that I've heard the term "non rotational valve train?

If every valve guide on the head is tight, guess what.... No rotate.

Op: your head builder fucked up and left the anti rotation key off one valve.....;-)

Please please please find a technical document (NOTa sales document, sorry) that covers non rotational poppet valve. I wanna see it.