Thank you for explaining the actual differences between the two engines. My original post was actually posted out of excitement that there may be a means of "pepping up" my 35_GT and I love the engine but it will not perform in the aircraft I want to fly that physicaly sized engine in. AeroWorks has a new [link=http://www.aero-works.net/store/detail.aspx?ID=308]35cc Extra 260[/link] that I thought would be ideal for a pepped up Evolution engine thus my excitement for the possibility. Due to the cost of purchacing a new 40cc and still not having anything to put my 35cc into (that I like) my excitement diminished in the second post