the other night i was driving down the road, and all of a sudden around 4k rpms my motor started to knock really loud.
so took it home. tinkerd with it a bit and gave up. no clue. next day i messed with it and if you pullout num. 1 plug wire it doesnt knock at all even to red line. put plug back on and starts again. thought num. 1 piston gone. did a compression test and 140-150 in all 4. so thought bearings so yanked out motor, and pulled oil pan and num. 1 rod moves alittle more than the others. so no clue. any help would be great.

 

spun rod bearing.

I am in the same boat.