Valve Stem Oil Seals
WARNING: This page does not describe the selected car, but rather 55 other vehicles, including the 1999 Oldsmobile Bravada, 1999 GMC Yukon, 1999 GMC Suburban, 1999 GMC Sonoma, and 1999 GMC Sierra. However, it is still accessible from the selected car via links, so may be relevant.
On 4.3L, intake valve uses upper "O" ring seal and lower umbrella seal; exhaust valve uses upper "O" ring seal. On 5.0L and 5.7L, intake and exhaust valves use upper "O" ring seal and lower umbrella seal. On 7.4L, intake and exhaust valves use lower umbrella seal. When installing umbrella seal, seat seal against valve guide boss on cylinder head. If equipped, coat upper "O" ring seal with engine oil before installation and ensure seal is not twisted when installed. A gap of.04-.08" (1-2 mm) must exist between edge of oil seal and valve guide. See Figure.