[WHY can't you just keep adjusting the tappets/shims up to get more duration?]
Hi,
I'm new to the rollaclub and would like to have a go at your questions.
Like Nick posted, valve clearance is required for different expansion rates of the engine. Also when the valve wears deeper into the valve seat, then valve clearance/adjustment is required. If you have your valve clearance adjusted too tight, you may not close the valve completely. If you have no clearance, you are not allowing the valve spring to close the valve onto the seat, and closing force will still be applied to the valve stem. That itself can provide you with interesting problems - like a drop in compression pressure or the posibility that you will start burning valves.
[what are the advantages/disadvantages/tradeoffs of adjusting valve clearance tighter for more performance?
]
Adv - no tappet noise on cold mornings :hammer:
