For a long time, carb'ed auto engines would run an exhaust passage through the intake manifold with the purpose of heating the air fuel mixture after the carb. The advantage is that heating helps to better atomize the fuel, with more even air fuel mixing, and provide smoother running engines, especially in cooler weather. The down side is that warmer air contains less O2 for a given volume than cooler air, due to differing densities and therefore slightly less power production for a given displacement.
FI engines can better atomize fuel and this practice generally went away with port-based, FI engines.
200* oil constantly flushing over the intake plenum will add a decent amount of heat to the air fuel mixture.
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 04-14-2021 at 01:33 PM.