Originally posted by AZ-LSB-M3
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1. was the chain tight on the pulling side (opposite side of the tensioner), and between the two sprockets? A little slack on the chain can cause cam timing retarded. When turning the crank to TDC, never ever turn it CCW to adjust the position.
2. You didn't know or verify that the EX piston was at its max forward before tighten up the 2 bolts pulling the vanos to the head. If the pistons were not at their max forward then while tightening the vanos to the head, the pistons could move instead of the pretensioned hubs move, leading to retarded timing.
To ensure that the pistons are at max forward, remove the caps, push pistons protrude out about 5mm, then bolt down the caps to set the pistons at max forward.
As about setting the 5mm gap between vanos and head, I would set this gap 10mm to give you more chances of pushing the pistons to their max forward during tightening up the vanos to the head.

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