A question for the locobuilders collective braib..

So assuming a "normal" car IE ford KA or VW polo.... that sort of thing.... is there a standard thread size and pitch for the sparkplug thread?

Most but not all car engines are M14x1.25 the normal reach (length) is 3/4". For thread repair first option is a special chasser repair tap, dosen't cost much and is usually enough to do the job. If the thread is beyond repair there are helicoils or solid thread insert kits available.

However some plugs are 10mm, 12mm or 18mm threads and plug reach varies.

You can check the thread on your engine by going to spark plug manufacturers web sites and de-cyphering the spark plug part number code letters.

Here is a link to the NGK downloadable car PDF catalogue Link to NGK Plug Catalogue
Page 9 has the info you need.

That is seriously useful! I can now select the ideal plug for the job Thanks for the link!