I know this is a common problem on modular engines but could this be one of the problems with my V10? I know it saw some hard use over its life at the railroad as well as alot of idling and Im wondering If thats the almost knocking sound im having, At about 1:44 the sound seems to quiet down but is still there

 

Mine also does this for a minute at starup. Is it common? Is there a fix?

 

i would say exhaust leak but that sounds like piston or crank slap. Ive heard ford's mod motors are know to get piston slap, id check the header bolts first but that sounds internal. I vote for the mod motor piston slap myself

 

your second video sound more like header bolt breakage, and it looked like you have the factory exhaust manifold still. Id check the header bolts first like i just said, im in the process of getting parts to change out my header bolts soon myself