Ticks often occur at the uppermost part of the engine, namely in the lifter and valve train components. There may be a little exhaust leak. Typically, knocks are caused by issues with lower end components such as main and rod bearings, or even a larger exhaust leak. Search for conspicuous soot marks in the vicinity of the exhaust. Occasionally, it is possible to detect the presence of a leak by physically feeling it with your hand. I would elevate the vehicle and inspect the underneath.