The Stovebolt Site Forums The Shop Area Engine Shop Heat riser or heat drifter??

I don't know if the engr's back in the day discovered they could improve the ICE's efficiency by heating the intake manifold directly under the carb by individual trial and error or if someone had documented it and they all subscribed to it but it's clear the American and German ICE engr's back in the day believed it did and implemented exhaust heated intake manifolds into their ICE designs.

Even tho the Stovebolt 6 has a temperature sensing heat to manifold regulator and the ACVW boxer 4 doesn't they both utilize heated air primarily at the junction where the downdraft carb meets the intake manifold and splits directions to improve ignition efficiency.

Since the ACVW doesn't have heated coolant circulating throughout the engine it's understandable why heated exhaust is used but the Stovebolt 6 has both heated sources and the engrs used heated air.
Was it cost or efficiency that drove that decision?
It's pretty Obvious that single carb'ed engines w/long intake manifolds work better when heated at the carb to manifold junction.
As already posted I would think heated air will heat up the manifold quicker than heated water but heated water would still be more desirable than having no heated manifold.

How about dual or triple carbs? Do they need manifold heat?
On the ACVW that goes to dual carbs the consensus is no. The manifolds are much shorted and very close to a heat source (the head) so warm up time is greatly diminished. Also of note is most of the duals are 2 BBls and don't even require a choke to start a cold engine. So after a very short warm up period dual carbed ACVW boxer 4 ICE's work very well without manifold heat and chokes....

In a Stovebolt 6 w/dual carbs we're still looking at somewhat long intake runners that are open and exposed to the cooling air of the radiator fan. In this case it seems to make sense that intake manifold heat will improve the engines efficiency.
Air or water is again more desireable than not.

What about 3 carbs? With each carb mounted directly over the intake runner that feeds the heads intake port?
This would almost seem to be the best method of increasing the engines efficiency and perhaps doing so without heating the manifold.
The engr's must have thought this back in the day when they designed the Blue Flame 6 for the 1st Vetts.

Course finding new carbs that will work w/the Stovebolt 6 in the tri-mount is the question and problem. There are several small venturi/adjustable jet 1bbl & 2bbl carbs widely available for the smaller ACVW boxer 4 and I wonder if anyone has tried any of these newer carbs in a Tri-mount Stovebolt 6 config?
And if so did they find it necessary to heat the intake manifold?

Anyways I'm rambling, good topic.
Dave