Valve Stem Oil Seals
WARNING: This page is about a different car, the 1995 Ford Windstar. However, it is still accessible from the selected car via links, so may be relevant.
Different types of valve stem oil seals are used on intake and exhaust valves. Ensure oil seal bottoms on valve guide. Oversize oil seals should be installed when using oversize valves. Intake valve stem oil seal can be identified by a White stripe.