I over rev'd engine ,collapsed a lifter ,motor began to knock at about 2000 rpm,when idling motor does not knock but oil pressure drops to almost zero & low oil light comes on , when starting motor it knocks bad for about 5 sec.replaced lifter still does same thing.Could it be cam bearings?

 

"Sounds" like a rod bearing. If you have a serious real knock, there is nothing to do but pull the engine and start tearing it down.

 

Thanks shoebox,but my buddy and myself listened to bottom end with screwdiver on oil pan & block while rveing motor & sound is up top Thanks again.

 

Never heard a cam brg knock.But wrist pins,broken piston skirts,rod &main brgs DO.I have explained how to tell a rod knock in several previous posts,mostly posts about oil pressure. If your existing knock is there all the time you may not hear a light rod knock and rods DON'T knock at idle unless they are fixing to window the block. Don't believe you will hear a rod by reving the engine either,but all the others you probably can.

 

This one I can answer bu personal experience! I am actually in the process of rebuilding my engine right now. I had a knock that sounded like valvetrain noise and after repeated valve adjustments and having the intake off numerous times replacing the lifters (all of them) I decided it was time to pull the engine. I got it out last night and I had smoked all of the bearings. No sh*t, ALL of them!!!! Looks like a main baering went bad and sent particles all through the bottom end wasting all the other bearings. I'm going to have to do the rod, main and cam bearings. Weird thing is, i had about 5 different people listen to it and everyone thought it was in the valvetrain. I replaces all aftermarket parts in the valvetrain with stock (known good) parts and it was still there. We started by taking off the heads and everything looked good.......so out the engine came. Not to try and make your problem sound worse than it might be, but................might be bearings!