Thanks for the comments.

Its never run low on oil or eaten anything that I know of. The air filter is in place and relatively new.

I have only started the engine briefly since the problem onset to record the noise. At idle of about 600 rpm the noise is a single knock that repeats roughly 6 x per second or roughly 360 beats per minute.

Thanks for the tip about car-part.com. I found a complete used engine locally but if i replace i'm thinking of a crate long block.

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