Jeff,

Depending on what kind of money you want to spend and how much power you need, there's no engine's out there that can come even close to a Jett engine. Check out his .46, .50, and .60L (same case as a .40) with Dub at http://www.jettengineering.com/ and you'll find out why. Also, you can read some of Dub's personal comments on each engine to learn more what's best for your application. Hope this help.

Sam