The Non-tuned crank has a bigger internal bore compared to the tuned but the tuned has alot more intake timing. There are pros and cons to both. The bigger bore slows the mixture velocity so the case doesn't pack as well so the engine will be smoother on the bottom and have less overall power. The Non tuned crank intake is small in diameter with a very short duration which will accellerate the mixture for a very short period of time to help maintain the velocity in the crank bore. The tuned crank has a smaller bore to keep the mixture velocity higher and with that needs more intake timing to get a better case fill. On the Non-tuned engines I have modified, I increase the intake timing beyond what the tuned version has and because the crank bore has a larger ID and the velocity will be a little slower, the extra induction timing gives the engine the case fill needed to perform well. To help round out the performance, I increse blowdown timing to give the engine a little more time to burn the increased cylinder pack and with that comes increased torque, peak horsepower and more rpm and depending on how you configure the timing will dictate he personality of the engine whether you want to hit hard and like a light switch or roll on power nice and smooth keeping the power to the ground. Thats a big reason why the two engine's have different running characteristics. The sleeves are the same, the stock port timing is the same, the compression is the same, the carb's are very similar, the cases are the same. The backplate's are slightly different but doesn't affect a thing and the rod's are slightly different also a non contributing factor to performance. Both team engines run side by side, hold the same temp and have the same milage. One with a knife edged rod and one without again proving an old myth wrong.