2 When we add the piston and connecting rod in, we’re including all primary elements of stroke. To get optimum displacement, both rod and piston dimensions must follow accordingly to get the piston deck height just right and clear crankshaft counterweights. Wristpin location and connecting rod length determine fitment as it relates to crankshaft rod journal throw. It doesn’t work if there’s conflict at bottom and top dead center. Rod length must be such where we get maximum dwell time at each end without contacting the crankshaft counterweights and cylinder head. This is known as rod ratio.