The only sticking valve I experienced was on my wedding day,(46 years ago), when my best man and I spent the morning trying everything short of removing the head to try and find the cause of the extremely rough running. If we'd only removed the head first we might have found the cause in time. The valve was sticking open as a result of a cracked tappet block possibly the result of over tightening the locknut during tappet setting in the long distant past. Needless to say I'm extra careful about tappet locknuts as a result. We had to go on honeymoon in a Mk1 HA Vauxhall Viva!
Fortunately I'd arranged the other wedding transport with the local undertaker (in the event, more reliable).......
Fortunately I'd arranged the other wedding transport with the local undertaker (in the event, more reliable).......