if you are removing the heads and your timing chain rails are old - without a shadow of doubt renew the rails and chain too.

The procedure I have seen is timing case after the heads - there is a youtube video of a russian mechanic assembling an M272 - its the same procedure.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)