ORIGINAL: Flyboy Dave
You would need increased port timing on the transfer ports,
I've got a couple of engines that might suit if it was only to have the transfer port timing closer to the exhaust. By eyeballing them (I haven't used a degree wheel yet) the transfers on both open at virtually the same time as the exhaust port. I've never seen any other engine like this. The engines in question? Believe it or not, the ST G20/15 and ST G15....hardly what you'd call wimps

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