I've had cars with summer/winter settings on the air intake that you had to swing around yourself. Summer air came from up front somewhere beside the radiator - winter air came from next to the exhaust manifold. One vehicle had an automatic valve that did the job for you. Another motor had no adjustment at all and the intake was from near the exhaust manifold - and in summer it suffered from vapour lock when the fuel boiled! I fixed that once I found out what it was. ...And I had a carb. freeze up running on the summer setting in winter! ...Anyone remember water heated intake manifolds? All these things done to get the engine up to - and keep it at a stable operating temperature - as quickly as possible.
I mostly remember the heated manifolds used as a common coolant port for the thermostat mount. and the exhaust as a source for choke control, and thekaz is right on, they were a were troublesome. You just hinted your age with the description of intake systems.
I used chickens for heating my engines, the best laying temp for them is 19C to 20 some degrees so I put several on top of my motor and it is warm in the morning and serves breakfast too.
