Valve Spring Shimming Procedure - Elimination
FILE IN SECTION: 6 - EngineBULLETIN NO.: 57-61-10
DATE: April, 1995
SUBJECT:
Elimination of Valve Spring Shimming Procedure
MODELS:
1993 Cadillac Allante
1993-95 Cadillac Eldorado and Seville
1994-95 Cadillac DeVille Concours
with 4.6L Northstar Engine (VINs Y, D - RPOs LD8, L37)
1995 Oldsmobile Aurora
with 4.0L Engine (VIN C - RPO L47)
Whenever servicing the cylinder heads of a 4.6L Northstar or 4.0L Aurora engine DO NOT use shims to increase valve spring load as stated in Section 6A2-Engine Mechanical of the appropriate service manual.
The tolerances of the valve springs at maximum camshaft lift do not allow enough clearance for the additional height of a shim. The addition of a shim will force the spring to "bottom-out" before the camshaft is at peak lift and cause serious cylinder head and/or valve train damage.
If low valve spring load is found during cylinder head service, replace the valve spring. Currently, the 1993-95 Engine Mechanical Sections of the Oldsmobile Aurora and Cadillac Allante, DeVille Concours, Seville and Eldorado Service Manuals contain the valve spring shimming procedure. This information should be omitted.