Duration is how you shift the powerband either lower or higher. If you want lots of torque at low RPM and don't care about high RPM (that's us), you want short duration rather than long. If you've upped the displacement of the engine by boring and/or stroking, you'll probably need to compensate for the lack of valve area by increasing the lift. The stock cam with high lift rockers is a step in the right direction, or the mildest of "street" cams. Lift is a good thing, but too much of it can lead to accelerated valve train wear. I don't think valve train (cam, lifter, rockers) is the big wear item on aircraft engines though, so that wouldn't be my determining factor, personally. You can just bolt on some higher lift rockers and get the higher lift, but there are other ramifications (that's for Dan's sake).
Stock cams are something like 226 degrees of duration with .315" inches of lift at the cam, and the mildest Engle 100 is 276 degrees of duration with .374" of lift at the cam. The Engle 100 would probably make a pretty good cam for a 2180 airplane engine, but I'm just guessing. I would think that Steve Bennett at www.GPASC.com would have a pretty good idea what cam works best for aircraft use, and if he sells them, I'm sure there's not much of a markup. His prices have always struck me as being very reasonable. I've been told that Webcam makes something called the P-100 that's good for aircraft use, but I just pulled that out of some pretty deep recesses, and there may not actually be any such thing. I think that's what was in the Type 4 that I bought from Mark Stephens. I just ran across this website at http://hometown.aol.com/dvandrews/cams.htm that pretty well explains the relationships of duration and lift. Mark Langford, Huntsville, Alabama N56ML "at" hiwaay.net see KR2S project at http://home.hiwaay.net/~langford
