This truck belongs to me and I guess thats a good thing, would not want to see this happen to one of my customers so here is the situation. 491000 km and working fine except having so detonation ping upon acceleration some times but not always. After carefully checking engine oil found a slight buildup around 5000 km, and after checking oil with paper towel I decided I was getting some fuel in the oil. So after checking injector balance at idle found them within limits next I decided to pull the injectors and have them checked. 1,3,5,7, went as normal , this is an LLY, went to do 2,4,6,8, OH 6 & 8 would not move-----try everything within reason, finally by using a long pry bar with the handle removed and the air chisel I was able to get #8 out, ruined the injector but it is out, injector hole packed with carbon and copper gasket black with carbon. # 6 could not get at it to get it loose but after welding a nut that matched the injector fitting to a heavy rod I was able to move the injector the few degrees that valve cover would alloy . After doing that for hours and raising blisters on hands and days of soaking with penetrating oils of different types and combustion system cleaner no success. Pulled engine today and after 3/4 hour with air chisel and bar on fitting I got the remainder of the injector out , Packed solid with gray carbon that mostly broke away and became powder when injector came out. I have not cleaned the injector holes completely yet but after using a small vacuum tube and looking at the injector seats in the head they look fairly clean and shinny and I don't see any cracks . Has anyone had this problem before and what is your experience concerning these heads--- no injector tubes on LLY. Thanks for your time and hope you had more fun reading than I had doing the work. Gary.

Gary Vernon
Owner/Technician
Gary Vernon Garage
Amherst, Nova Scotia, Canada