Inlet (and exhaust especially) valves have a hard life, and eventually become brittle and beyond a simple
Valve grind to restore the engines full performance. This is the point where new valves make more sense, especially if carrying out a full cylinder head or complete engine rebuild.
Renewing these
Valve Retention Cotters (or collets as they are sometimes referred to) at the same time is a sensible precaution!
Ensure all the parts you require have been ordered valves, Valve springs, Valve stem seals. Try this gasket sealant: 08C70K0234M the choice of the factory professionals.