Last night I adjusted the valves on my 73' "F". I timed the engine by ear (first mistake). I was dri ving a long today and started to get a bad knocking on my way to the trail head. No matter which way I adjusted the distributer the knocking persisted. I re cheched the valves and they where good. I ended up towing it home in fear of blowing a rod. Did I really mess it up? What do you think the knocking is? What should I look for if I take the engine apart?