I would appreciate any insight anyone can give me on typical clearance for exhaust valve stem clearance to exhaust guide. The exhaust valve stem mic's .3745 (stock size). The other heads good guide measures .380 ID. The heads are 10 plus years old so I am assuming these hav worn some. These are STD heads using cast iron guides and stem seals. The heads were purchased new and assembled and there was no accompaning paper work.