Exhaust leaks was the reason for the work. I had to remove the heads to plug those little smog holes.
I have pinpointed the tick to one of the number 3 valves with the red-neck stethoscope (wood stick).
If it's a hydraulic cam with non-adjustable valvetrain, it might be an exhaust leak. Re-check your torque on your exhaust manifolds or headers to cylinder heads, you'll probably find one or two that loosened up.