cold engine start clicking noise, what is it?

I replaced my fuel filter on my 2003 2.4L tacoma 2wd. 65k miles. At the same time I checked the valves. No valve adjustment needed. Now I hear 4 to 6 rapid metallic clicks when i start the engine cold. Once it happened when it was warm. This fuel filter is not original equipment.

ideas?

tks,
pa

Could be the lifters ticking till the oil gets back to the top of the engine

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