Oversquare Motors Build, (Shorter Stroke, Bigger Piston Build) |
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Oversquare Motors Build, (Shorter Stroke, Bigger Piston Build) |
tjtryon |
Oct 26 2023, 10:04 AM
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#1
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Newbie Group: Members Posts: 20 Joined: 15-June 16 From: Indianapolis Member No.: 20,112 Region Association: None |
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? |
Superhawk996 |
Oct 26 2023, 10:21 AM
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#2
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914 Guru Group: Members Posts: 5,903 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Heat rejection and deformation of cylinders is a big problem with cylinders larger than about 96mm.
Look into Nickies for any big bore projects. |
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