glow plugs SXI vectra 2.2DTI what tap

[jimmy495]

hi to all just got all my glow plug's out of my 2.2 dti with out them snapping great used lots of WD40. but when i got them out and looked at the threads they are damaged went to put the new ones in and they are tight. so stopped the last thing i want to do is snap the new ones putting them back in. so got a piece of alloy plate drilled a hole in at 8.5 mm and used a m10-1.25 pitch tap then a m10-1.5 pitch then a m10-1 pitch tap.
now then does any one no what tap i should use i think the m10-1 pitch is the best fit. would like to know before i tap the head tomorrow
many thanks jimmy

[jimmy495]

any one no