Originally Posted by stevieturbo

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.