Thanks for all the input on what was causing the "knock". I tried compression tests, pulling wires to "isolate" the cylinder, checked the rod bearings (OK), removed the side pan (nothing amiss). Couldn't get to / solve the problem. Got tired of working under the carport in the WV, December (cold) weather and had the truck towed to a local garage / trusted mechanic. After engine removal and a complete teardown, the fiber gear on the camshaft was found to be missing 5 teeth! Don't know how it started and ran under that condition, but that was the cause of the noise. No damage to cam, crank or vitals, but a rebuild is in the works. BW
