I have some old 2 cylinder industrial engines, newer than "hit and miss" engines but not a lot newer. One make, LeRoi, has pistons that both travel up together, and the other, Novo, has one up one down. They're both reasonably smooth and run nicely but the one up one down engine jumps around less.

•1951 GMC 250 in the Project Journals
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•1952 Chevrolet 3800 pickup
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