I agree a heavier motor on a rough or slick track will be as fast as the light motors. Unfortunately the importance of the light motors shows during qualifying when the track is sticky and can take all the power you have. This is especially true in WoO competition where a bad qualifying attempt will bury you for the night. There is one sanctioning group (http://www.nosasprints.com/) which has a bit of a compromise for the engine weight debate. I believe their rules are setup for steel based 410's but allow for aluminum blocks if they bolt on weight in specific areas of the motor plate. This allows people to run cheaper steel motors and also allows those who choose to run at other tracks with open 410 rules the easy switch of unbolting the weight.