[hamjet]

I'd be concerned using a block of wood to hit against. if its soft wood like pine you're liable to sink the valve stem into the wood and then when the wood makes contact with the retainer you're likely to pop the keepers out and the spring will pop out. Be carful you don't hit on the retainer, thats all. Worst case is you'll have to pull the head and get it cleaned up with valve job. Unusual for the intake to get gummed up.