The old piston dome looks like the one for the SD engine. (thought they had a different part #?)
Most though end up milling those bumps done which would look about like the new piston you have.
The old SD piston had a .476" dome but don't know what the cc is. Supposedly 10.12 at standard bore and 111cc head chamber.
Since you know the new cc's use that in the calculator to see what the CR would be. The old set would be approximately .25/.50 more CR I'd say?
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John Wallace - johnta1
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