1999 Suburban Ticks cold

Hello, I bought this Suburban several years ago Some specs on the vehicle it is a suburban k1500 it now has 175k miles engine replaced at 143k Shortly after the purchase of this vehicle I had to overcome some serious problems with the intake manifold gaskets leaking antifreeze, this eventually ended in a major bearing failure and engine replacement. I went out and bought a crate long block and after minor bugs I found this motor had a valve tick on its right bank. I tried resolving this by removing the valve covers and tightening on the rocker arm making the noise. My mechanic thought it was a collapsed lifter so we went ahead and replaced all of the lifters. Since then I can say the tick is still there, I know all the push rods were intermingled, all I can think of now is that the cam lobe on the cam must be cut too low. I really could use some suggestions here. I tried to call the motor builders for the long block but of course they fumbled the warranty as expected and by now it is null and void. I don't like the sound of the engine as it sounds like a sewing machine on start up. My mechanic tells me there is some bulletin that states you should add some bottle of some additive to reduce this noise. My theory is that nothing you buy in a bottle to fix a problem ever works. Please let me know what you think. Thank you in advance.