Do Model A Engine Valves Rotate?

[Marshall V. Daut]

I'm pretty sure my Ron Kelley engine from the late 1990's had rotators on the exhaust valves. He said it keeps the hard-working exhaust valves from seating in the same place every time. It's supposed to keep the valve from getting too hot, although I'm not sure how that is effected. I don't recall if Ron installed stronger springs with the rotators.
Marshall