Hey i have a 2003 Ford f150 with the 4.6L. it has roughley 135k miles. i went to crank the other morning in about 40 degree weather and it made a heck of a noise. i pulled the driver side valve cover and found that all the exhaust vavle rockers were snapped in two. pulled passenger side and all was in tacted. if anyone has suggestions or commets about this problem please let me know. could it have been the oil? weather? etc. also how hard is it to change and replace and were is the best priced parts. thx to all. Justin of savannah

 

Sounds like for some reason the exhaust valves stuck closed on that side. I have no idea of what would have caused that. I would look at Jegs or Summit or a local parts distributor. As far as changing them, if the cam is underneath it should just be pull and replace. I would look and see if a manual has anything on it.