TSB's

Coated Cam Bearings

GM now recommends any cam bearing replacement in a Gen IV V8 engine (LS series) to use coated cam bearings in all five positions.

The new cam bearings feature a black polymer coating. Note that if the black coating wears off, this does not indicate a bad bearing. There is still a lead lining material underneath.

Of course, if the lining is damaged or worn beyond specification, replacement is required. The maximum cam journal to bearing oil clearance is 0.005-inch on engines equipped with AFM or CMP. Maximum oil clearance for engines not equipped with AFM or CMP is 0.006-inch.

Refer to the GM parts catalog for cam bearing part numbers, which will be different for positions (1 and 5 use the same part number, positions 2 and 4 use the same, and position 3 features a separate part number). Part numbers will also differ based on the use of iron or aluminum blocks.

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