I recently had head gaskets replaced in my 99 F 250 LD 5.4. The shop that did the repair recommended planing the heads to correct the twist in one. The manual at the machine shop states that you CAN plane to a maximum of 10 thousands , but no more . All that was needed and milled was 5 thousands. The job completed and every thing appears good. Just before this repair was done i had fault code P0174 Lean Bank #2. So now the gasket repair is completed i take my truck to a Ford dealership and ask them to scan and see what needs to be done to correct. I inform them i have a K&N cold air intake and the heads were just planed and new gaskets put in. After about 4 hours of diagnostics they tell me there was a piece of thread on my MAF and it is not in spec,but might not be the problem. So they phone Tech hot line and they say check Fuel Trims at steady RPM's. If readings go opposite of each other on each bank then likely a timing issue. So now the Dealership says the heads can NOT be planed and shouldn't have,this could cause timing prblem. They recommend replace the heads at $$$$$$$$ expense. My question is Can these heads be machined or not..is this the cause of P0174??

 

i dont think .005 inch off the head face is noticable. the dealer or his rep is full of crap. i can not be that touchy. now .100 might be another story, but not 5 thou.

 

5 tousands is hardly anything. You will have a little more compression but not enough to tell. Are you using 87 octane right now? Try going up a grade and see what that does, it should change the timing.