I recently purchase a 1 ton dulley that had a bad cam. Removed heads and had valve job and replaced three bent valves and bad exhaust guides, installed new cam lifters and timing chain. Started truck to break in cam ran good for about 3 minutes with 60 psi oil pressure. Oil pressure started vibrating between 30 to 60 then went to 0 I shut the engine off. Talked to several people the consensus is I have a spun rod bearing and that starved the cam of oil causing the cam failure. Before I pull the engine does anyone have any other ideas?