Doc here,

imp:
Get a Stethoscope, and start and IDLE the engine to warm..
If you don't have one you can make one from a 1/2 PCV pipe..just put an end cap on the end that goes to your ear..make it about 4 feet long..
Place it at the lower end and LISTEN, If you hear knocking..move the end rearward until the knocking is loudest..not what cylinder it is..If not sure of the bank..Pull the plug wire on one bank and listen..If it still knocks, replace the first wire and pull the opposite bank wire.. until the knocking gets quiet..That's your offender..
Pull the plugs, drop the pan and pull the big end cap. Inspect the bearing for wear..Then inspect the Journal..If it looks like it will play on an Edison phonograph, you'll need to pull the engine, disassemble the WHOLE engine, remove the crank and get it to a machine shop..
it must be turned under-size (provided it isn't past runout) Bring the stripped block, rods, and heads with you , have them all hot tanked, Rods checked for straightness, and stretch, Have the machinist Fit the bearing set to the crank.
Have new cam bearings installed..Take the engine home, Hose it down with a pressure washer, paint or "pretty"it up or whatever you want to do, make a 100% CLEAN working area..and re~assemble your engine.. Make sure you check clearances, and use proper torque specifications. Get a rebuild kit..cheaper then one part at a time, HAVE your machinist select it for you so he can match / install the bearings.
you need to be absolutely SURE the engine is pressure washed before you assemble and paint to remove any machine dust..and any metal chips that may be hiding in the gallery's other wise you'll be doing it again soon..
Low oil pressure, dirt and low oil as well as OVER~REVING can cause this ALL of which are under your control..
Doc

imp: