Here's a question

[02GF74]

Would the rear pair of cylinders run hotter than the front pair?

Assuming the water jacket and water flow is equal to both pairs, the front pair get cooling air from the radiator (air will have absorbed heat but would still be cooler than the water) and the front exhaust headers sit in the air flow.

So could running different heat rated spark plugs could be beneficial. (I suspect the temperature difference is too small to be of consequence).

 

[Fire-medic]

I suspect so, rears hotter that those in the front. Throw an infrared thermometer on 'em and find out. About the plugs being different heat ranges, I cannot answer if it would do any good, but I have heard about that being done, though I cannot recall for what vehicles. Maybe more of a thing on air-cooled engines. Think of water-cooled engines, and the first cyl in an inline-6 mounted longitudinally, having the same heat range as the rearmost.

 

[one2dmax]

That is the nice thing about water cooled. The difference is minimal so even tuning for all cylinders.