LOL!!! I did that to mine in about 1973!!! Pretty sure my first one was a KD.
I'm with the others you MUST "bump" the retainers to get them unstuck. I use a socket large enough to clear the valve/ retainers but small enough to not slide off the retainer. Don't hit it real hard, and have the head jacked up (if removed) on some rags and scrap wood. That way you won't accidently drive the valve heads against the bench