[blucar]

There are two factors at work with the heat risers on any engine...
Stock, or near stock engines love the heat risers, the fuel is properly pre-heated for complete vaporization..
Speed freaks love to block/eliminate the heat risers because the exhaust makes more noise, which givers the impression of more power.
In the real world, elimination of the heat riser will make an engine run rich.
When I was young and foolish we would block off the heat riser ports in a Ford flat-head by sliding a piece of shim stock or thin metal from a pipe tabacco can between the intake gasket and the block... When the weather cooled, or we were tired of the added noise of the pipes, we would loosen the manifold bolts, with-draw the metal and re-tighten the bolts.
The whole subject boils down to.... do you want reliability or do you want noise?