Oversquare Motors Build, (Shorter Stroke, Bigger Piston Build) Options

[tjtryon]

Good Morning!

I'm looking at a rebuild of my 1973 2.0 Motor. When I raced motorcycles, I was constantly rebuilding my motors, chasing the speeds I want, and putting the power where I wanted it in my motor RPM. One thing I (and most that I raced with) did was rebuilding with an over-square motor build. The 2.0 914 Type 4 motor has a stock stroke & bore of 94mm (bore-cylinder width) and 71mm (stroke - piston travel). By moving to a shorter stroke, such as 68mm, the piston would move less in the cylinders, which would allow me to run a bigger piston with less stress on the piston (rings move less causing less friction and less heat) allowing me to run a bigger piston, and would move max power higher up in the RPM range, and allow for a higher max RPM. Less movement for the piston would cause less movement on the rods and crank as well.


My thoughts are to run 103mm pistons, and a crank of 68mm, allowing for a displacement of a 2.3l (2266 cc). I've been looking into a Falicon forged crank, Carrillo Titanium Rods and JE forged pistons. I think this could allow for a much stronger engine than any other I would have.

Does anyone here have any experience with a short stroke, big bore motor? How about those engine builders reading through this? Any thoughts or experiences?