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Smoother surfaces, less friction, less wear, increased longevity.

So generally a better engine. Why aren't all that way?

Cost

> What does polishing the timing chain accomplish? Or is it more “accurate” timing?

I’m also curious, in terms of idling and the longevity of the engine. It has to be said, those old Crown Vics are still on the road.

Likely the cop/cab version uses a roller timing chain, which is lower friction that the typical stock chain.

The timing chain is splash lubricated and at idle there isn’t enough oil pressure to produce much splash. The high polish reduces friction particularly when there is little oil.