Define knocking. Is it knocking as in a deep thumping, or a tapping clacking higher pitched click?
Worst case scenario, deep thump MIGHT indicate a spun big end Connecting rod bearing which allows the connecting rod to knock back and forth on the crank. Mucho worst case.
Best case scenario, ticking might be as simple as a dirty fuel injector.
There are at least a dozen other things in between.
130 total pounds of Pitbull ruled by 8 pounds of cat.