If your 5.3-liter engine is ticking, there are several possible causes. The most common cause of engine ticking is worn valve lifters or rocker arms. If the valve lifters are worn, they can't properly hold the valves open, causing them to tick. Worn rocker arms can also cause similar problems.
Another possible cause of engine ticking is a loose spark plug. A loose spark plug can produce a misfire, which will cause the engine to tick.
Finally, low oil pressure can also cause an engine to tick. If the oil pressure is too low, the moving parts in the engine will not be properly lubricated, causing them to wear out more quickly and producing a ticking sound.