As I recall from stories about the older GM 454/455 and the Ford 460 (I had an '85 460), the manifolds can get to a cherry red color when climbing hills at full throttle and low speeds. That's up around 800 Celsius if I remember my engineering heat treatment numbers correctly. There's a fair amount of air blowing through there, but the radiant heat must be tremendous.
Frank Damp -Anacortes, WA,(DW- Eileen)
ex-pat Brits (1968) and now ex-RVers, as of 08 Dec 14.