Finally, we get to the main reason for this engine build. Cleveland heads that feature a closed combustion chamber design for good compression and an effective squish pattern. The 57cc combustion chambers combined with the 3.500-inch stroke will produce a 12.5:1 compression ratio. Make sure to look for the “2V” heads that were designed for a two-barrel carb. The larger 4V heads have intake ports that are too large and will leave you with poor throttle response.