if you have a bottom end knock you are wasting your time with that engine.
replace it.

bottom end knocks are rare in b230 non turbo engines that have never:

1. been run after blowing the head gasket until all the oil is also gone
2. been run with very very low oil pressure (single digit) for a long time
3. obscenely over revved in low gears

the amount of square inches of the 5 main bearings make a bad main nearly impossible. the usual suspect for a low end knock is rod bearing. still very unusual.

i have seen only 2 among a multitude of b230 repairs.

number 1 above was the first and second was moron/sleaze in vermont who hit a rock with his oil pan breaking off the oil pump and then drove the car for another 2.5 to 3,000 miles before selling it to me with the oil pressure light of course disconnected.........who me?
the amazing thing was the oil pressure was still 12psi and the main bearings were fine. it was the rod bearing which showed wear.