Most bang for the buck.

The K&B should get me about 12,000 RPM with a 11.5x7 prop ($135.00). The tuned pipe should raise the RPM to 13,000 ($110.00). Tower Hobbies .75 ABC should give 15,000-16,000 RPM (as they state in their catalog) for about $100.00. There is a small weight gain for the tower engine but it seems to have a lot more power. I know Clarence Lee Modified K&B .61 engines have a good rep...however, I am looking for the best bang for the buck with speed being the main factor.

Which way should I go?