A "typical" 509 is built with a 4.500" bore and a 4.000" stroke crank. I've been considering doing a 509 build using a 4.500" crank instead and a smaller bore size (4.240")... 508.3 cubes. A couple of reasons: I am seriously contemplating the use of an aluminum BBC block (Bill Mitchell Merlin-X) which supports a maximum crank size of 4.500"... if I simply go to the max on the bore size (4.600") it will end up at just under 600 cubes. This may be a case of "simply too much" engine, even for a heavy K5. My thought was to use the 4.500" crank (and only have to buy an expensive crank once!) and use the "factory bore" of 4.240" to build up a much smaller 509-inch motor. I could run it in that configuration for a while and if I didn't scare the bejeezus out of myself, I'd always have the option of boring the block for more cubes.....but re-using the rods and crank to build a 600-inch monster. The main question is really what the effect would be of building a 509 with this "oddball" configuration (small bore, large stroke)?? My suspicion is that the torque curve would move substantially lower in the RPM range (more torque sooner) which would be a welcome thing. I'd love a big FLAT torque curve that reached it's peak VERY early and would stay flat all the way out to something like 5000RPM (or more). Has anyone run a DesktopDyno on confgurations with exaggerated stroke lengths? Dyno charts? Real World experiences?? Right now, this is still in the early planning stages....but Bill Mitchells shop is only about 5 hours away, so the temptation to have him build me something and watch it run on his dyno is very tempting!!