A 170 will rev higher then a 225, or a 198 for that matter. The 170 has a shorter stroke then a 225, or a 198, or even a 170 made into a 198. The 170 crank is lighter, then the 225 or 198, as are the rods (stock) and the pistons all weigh the same (stock). If using after market "race" parts that can change. Just remember the old saying, "speed costs money, how fast do you want to spend".
