Sound from valves or rods???

[TDK08]

I am doing some research for my dad. The Motor is in a boat, if that matters. It is a 2007 5.7 Vortec series motor.

At WOT there is a noticibable ticking noise, but it doesnt do it at low or mid rpm's...

What do you guys think?

[TXsilverado]

does it sound like your pieces of rice onto a sheet of aluminum foil?

[truckinL33]

Detonation?

[gm327]

if its the tick tock , sewing machine sound.. you could have a valve float.