Does a timing chain (as opposed to timing belt) need any specific maintenance? In particular I'm talking about a BMW Z4
While regular maintenance is not required, it is advisable to regularly check how much the chain has stretched, say every few 100K. If the chain stretches too much, the tensioner may no longer be able to perform its job. There's also the problem of the pins becoming a bit loose in the side plates.
The chain should also get a visual check whenever the opportunity presents itself to ensure there is no evidence of things like side plates starting to become loose. Rollers should be felt to ensure there is no discernible play between roller and pin.
Timing chains don't often break but when they do they generally take chunks of the engine with them, as well as allowing valves to get too friendly with the pistons, on most engines.
Regular maintenance is not needed. However, a "rattling" noise that changes with engine RPM may indicate a problem with the chain or timing gears. Usually this isn't an issue until higher mileage (150k +).
Next time you go by your dealership, ask them if they've had any problems in particular with your year model. If you hear of instances of chains commonly being replaced at X miles because of some problem (and you trust your source), then you may want to take preemptive action.
BMW timing chains are engineered for the life of the engine and never need maintenance or replaced. To prove that point BMW has always performed several long distance tests on its new engines before they are put on the market. Back in the 90s they took a e34 (5 series) and ran it over 2 million miles, just performing the standard maintenance. When they took apart that engine everything measured to spec.
Enjoy your Bimmer and just make sure to get the regular maintenance performed but no need to worry about the timing chain. Now if you're a e30 guy like myself, you're stuck with the single worst decision (sorry second worst, after hiring Chris Bangle) Bimmer engineers made and that was to go with a 'quieter' rubber band timing belt. Argghh!!
Long chains will get loose sooner, hard shifting will knock it around and shorten its life, infrequent oil changes will interfere with lubrication as the carbon builds up on the chain. Most engines either have an automatic tensioner, or a good guide to help it from slapping. Belts are good, but some are very hard to change. Too bad manufacturers don't try to make the belt easier to change as it is needed to be replaced at some significant expense.