Sorry about that! Didn't mean to turn your question into playtime here and I understand your situation. When you say "wide open throttle," is that with the governor operating (3600 RPM) or is your engine ungoverned? If there is excess wear on the connecting rod you'll hear knocking when the engine is under a load. You can hold the brake and give it throttle at the same time to really load the engine. It could also be piston slap, that makes a knocking sound. If you're running it at much higher RPM than the engine is designed for you could be getting valve float.