"Inside the valve guide"????? I don't think I've ever seen a guide with a groove for a seal like that. There is an aftermarket "umbrella" style seal that slips onto the valve stem before the spring and retainer is installed, but if you use that type of seal, DO NOT also use the O ring under the split keepers. It's possible to do too good a job of sealing oil and wear the guides out from lack of lubrication. Use either the umbrella seals (not included in a head gasket set) or the O rings, but not both at the same time!
Jerry
