Ticking noise coming from passenger side, front under valve cover.

I bought my truck new in 2007. I don't put many miles as I live a mile and two tenths from work. Actual mileage is a little under 27,000 miles. Over the past year it has developed a tick/knock on the passenger side front under the valve cover. I did a lot of research and decided on cam phasers. I ordered all the necessary parts and tools to replace them and also a repair manual. I got as far as pulling the valve cover off to discover that it does not have cam phasers. I have also read that the VCT solenoids when it goes out causes a tick but I read where to look but are also not installed on my truck. Very confused and what steps do I take next to solve the problem. I have read there are a lot of problems with these motors built from 04 to 08. The truck still looks new no damage dirt or rust. Any help you can give me on tis would be deeply appreciated. It is has been parked for five months. I don't want to cause any additional damage to the engine.