my 99 chevy suburban had valve train noise so I changed the engine and it still has valve train noise. Could it be the remote oil cooler ? That is the only thing that was not changed when I installed a new engine. It only has the noise for the first few minutes when it is cold then after that it runs great

 

Did you put in a brand new motor? You probably replaced a motor with piston slap with another one that also has it. This common for motors from those years.