Interesting thread. I was taught valves should rotate for the obvious benefits. Is that still true? Are there other factors that rotate the valves beyond the keeper issue? Am unaware of any valve issues due to them not rotating.
Im not a fan of letting the valves rotate. But that's what some of the keepers were designed to do. With multiple grooves and the keepers butting the valve will spin in the retainer like the knob on a shithouse door. That may be ok for a dead stock deal (I say don't let the rotate) but on ANY performance deal I don't want the valve moving. There is no reason to add another harmonic into the valve train that just doesn't need to be there.
Then grab a single groove lock that doesn't butt and put the retainer on and you won't be able to turn the valve.
Back in the day, the engineers wanted the valves turning to keep carbon from building up on the seats. Today, if you have carbon issues on a seat you need to fix your engine. Plus, engine speeds were much lower than they are today.
Also, multi groove locks with solid lifter cams is a disaster waiting to happen.
