My engine developed a ticking noise similar to loose rock arms only not quite as loud at RPMs of 3000 and higher. Basicly, at 3000 and above it sound like the whole valvet train went loose at the same time or it's pingin realy loudly. I've adjusted the valve-train countless times and they are new heads. I thought it might have been worn valve guides at first so I had them rebuilt and opened up a bit too. The motor is fresh too. Could this be a timing issue? or too cold of a spark? I am thinking of trying hotter plugs. Has anyone here ever had a similar problem?