Glow plugs are 1/4"-32. Your not going to find a Helicoil kit for them at the hardware.

I must ad here that 1/4"-32 is a unusual thread dimension. 1/4"-20 is the standard course thread and 1/4"-28 is the standard fine thread. The 1/4"-32 would be a special size in a tap or in a Helicoil. I do have one, I cannot remember where I got it but it was at a hobby shop or from Tower?

Send the head to C.F.Lee. His address is in the back of RCM. I don't have one in front of me right now. Perhaps someone else can chime in here and give us Clarence's address? He caharges about $8.

Jim