Spark plug size ???

[DAVE C]

looking for spark plug size for 0540 lycoming for cht sensor they list them for 10mm 14mm and 18mm denso plugs Thanks

 

[Slidin Gator]

18 mm spark plug threads. Note that I have found the spark plug base temp readings (using laser heat gun, not ring CHT) to be 50 to 100 Deg F less than the bayonet CHT's that Lycoming specifies.