Steve, There are new intake valves for the Continental, also - suitable for 100LL, which still has more lead than 80 octane did.
I don't think there is a requirement to replace the older valves, but the shop will want to do so - at a significant price for the new valves. I chose to keep the older vqalves when I did a top overhaul..but you can only do this if the old valves will clean up within specs. I don't think the older valves are available. I believe the change only has to do with the face angle, creating a larger force on the interface of the valve and the seat, to "chip off any lead deposits". Regards Harry
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