Originally Posted by
Caddyshack
isn’t it the other way round that a hotter plug is actually cooling the engine as it acts as a heat sink…pretty sure that is the case on 2 strokes anyway, when a 2 stroke makes more power you go up a number to help cool the engine.
Nothing like that.
Quite simply a hotter plug runs hotter, it's irrelevant to engine cooling. Only plug temperature itself. But a hotter plug in the chamber may be more prone to detonation....but compared to most engines, 9 is bonkers cold.
I've run other 4cyls close to 1000hp and wouldn't use 9's. But obviously Ford/Cosworth felt the need for such cold plugs for some reason.