Chain tensioner is tensioned by oil pressure and spring pressure; and your mechanics are likely supervised to make sure they are doing things properly. There is little doubt they did a superb job -- just make sure your chain rails have been replaced recently (within 5 years), as this is the primary reason for engine failure on a properly maintained M116/117 V-8 engine. They should be white, or slightly vanilla/off-white; if they are brown or orange, plan on replacing soon, after you have verified the integrity of the right-side chain rail. And be careful turning the engine over w/ the starter while the valve covers are off -- even though you have a new timing chain and there is not quite enough slack to skip if the tensioner relaxes, the valve covers keep the chain on the cam sprocket from skipping if this is even a remote possibility, due to slack created by an old chain and/or tensioner.

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