Yes, agree with using bio rather then petroleum based. I have not taken anything apart yet, but is it feasible to soak inside of Plug with biodiesel? Will it damage to the head/cyl/rings? Would imagine best to vacuum out an crank to expel as much as possible.

Any thought on worth it or not to try this? On the flip it may actually make matters worse. It may loosening up the carbon weld/build up which secures the gp tip to the head. If the gp breaks at the thread. When you drill out to remove, the tip may fall into the head .

I also agree heat/expansion works in your favor. Do you prep the intake manifold before warming up? Loosen the lower intake hose bolt prior to heating up engine? Try to minimize the amount of work needed to take of manifold once engine is warm/hot. Any suggestions to prep removal steps prior to warming up engine? Or, do you just remove the intake as normal when engine is hot/warm?

Thanks in advance.