Maybe this is Deja Vu...I'd swear that I (and others) answered this question a week or more ago. You need to lower the cylinder in the crankcase and shim the head to lower the compression back to where it was (and beyond). This will lower the timing and it will make a torquier engine. You can bore the top of the crankcase or you can turn the lower side of the liner flange. The latter is the simpler way from a machining standpoint and also less financially ruinous in case it is botched. Another way to do the same thing is to make a longer conrod, in which case you are raising the piston relative to the cylinder, and again, you need to shim or machine the head to reduce compression. If you make a
rod, you can leave it unbushed until you decide if it works as you want, then bush it. Use 2024-T6 alloy. Steve