From the reading I've done, the smaller OS LA engines are good. I've also read good feedback on Thunder Tiger and Magnum engines. Some specifics include the OS .15LA, it gets really good reviews. I saw one in a combat mustang a couple weeks ago. Faster than anything else out there. I've got a Thunder Tiger Pro-36. It's got good power and weight, and a reasonable price. I've also got several older OS engines, 25FSR, 25F ABC, and 32FSR that still run strong and have comparable power to today's engines.