[beatr911]

Have not done it but have some info.

Many old carbureted (and early EFI ) vehicles have a vacuum acutated heated intake that regulates temp at about 100*F. These have a bimetallic strip valve mounted on the clean side of the air cleaner. There is a vacuum diaphram controlled by the strip that regulates hot air from the exhaust manifold and cooler air from outside. The bimetallic strip bends at a certain temp and bleeds vacuum air to the diaphram thereby regulating the intake air temp. These are really simple devices and in my experince very reliable too. Sorry, don't have a diagram available.

The beauty of this is that at low vacuum (wide open throttle) the vacuum is not enough to pull the diaphram to feed warm air, so full cold air is fed when most needed for power. When vacuum is restored at partial throttle it's back to 100*F air. Best of all, the exposed versions of the bi-metallic strips are actually tuneable so you can play with the regulated intake temp that suits your engine, within a certain range of course.

The two vehicles I had that had this were: '72 Datsun 510, '95 Dodge Caravan, but they were also widespread on other vehicles from the early 70's to late 80's. If you see a vacuum diaphram on the air snorkel of a suspect vehicle, you've found one of these systems.