Changed wires, plugs, dist cap and rotor two weeks ago. Yesterday the engine started making a loud knocking sound. Sounds like the valves are tapping. I checked all fluids and everything is at the proper levels. It doesn't make the noise in park only when you drive it and put a load on it. Was told possibly water pump but checked that and it's not loose.

 

Only thing i can think of would be a mis aligned plug wire. maybe double check them to make sure they are going to the proper plug. Also i have had a distributer cap come loose and the rotor was tapping the pegs in the cap and sounded alot like what you are talking about. just some things to check