Since your talking about a 3.5l 603 motor-


First, know that that engine is known to have reliability issues.

The only TSB on chain strech that comes to mind is excess oil consumption. Generally, you measure the chain stretch and replace it at about 5-6 degrees.

Rotate the engine around till the cameshaft is at the alignement mark, read the crackshaft.


Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E