4.390 bore x 4.300 stroke. I'm not too worried about the combination. We're using the parts that Kaase recommends and he has built a ton of these engines. Once we get some dyno time on it we'll start trying different things but the first build will follow the Kaase plan. The cam is his "small" one since we have a smaller engine, but the duration at 0.400 is 91 degrees so the intake valves are open more than 0.700 for a quarter rotation of the engine.