Since the basic design of a stovebolt engine dates back to the late 1920s or early 30s, there's a very limited number of options for improving the performance. These old boat anchors are more or less glorified tractor engines, mostly designed to pull heavy loads at moderate speeds with long stroke crankshafts at low RPMs. The only viable performance improvements are going to happen in the low end of the RPM range, with moderate increases in compression, and/or more cubic inches. I've been working on various methods to increase the stroke on 235 crankshafts, up to about 3/8" or slightly more, and adapting connecting rods and pistons from other engines to make up for the difference in dimensions that changing the stroke involves. That requires some pretty sophisticated machining modifications, involving using non-original parts from other brands and years of engines- - - -flathead Ford V8 connecting rods, rod bearings for a Jeep 4 cylinder engine, and pistons from Japanese Diesel engines, etc.
External modifications such as multiple carburetors, dual exhausts, etc. look good, but they can only offer a very limited improvement in performance unless some pretty extensive internal engine mods are also done at the same time.
Jerry
