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You can implement VVT with gear-driven cams. The mechanism for variable timing is in the gear on the camshaft, anyway, and doesn't care whether it's belt, chain or gear driven.
But those systems are complex and noisy. Almost completely maintenance free, though.
Chains are lovely. Have hardly ever had one break or heard of one breaking, except as a freak accident. If I recall right, manufacturers started going back to belts for reasons of noise, as chains are a bit noisier than belts... but given direct injection is so clattery that they've resorted to using more insulation around the engine, I don't think the extra noise is much of a problem, anymore.
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