Carbureted cars built since the 70s have an alternate air inlet controlled by a vacuum motor which in turn is controlled by a thermostatic switch or valve placed in the air stream. The alternate air is drawn across a stove built onto the exhaust manifold. Older models had a bimetal spring controlling the alternate air valve.
Put succinctly - Automatic Carb Heat.
and there is a longer length of exhaust system, allowing more heat loss before the gases get dispersed in the atmosphere.
Exactly ! - also aircraft engines tend to have a hotter exhaust than their automotive counterparts. Silencer contains numerous passages/baffles to collect moisture after shut down - errm - turning the car off and it is this moisture that turns to steam once the engine is restarted. This is why a standard (non-stainless) exhaust system on a car driven on the highway will outlast its city driven counterpart.
I used to have a zooped up mini
Must've been loads of fun !
