Guys, expert input needed below. [Ed]
Stan wrote: >>>>> Thanks a lot for your reply. The reason why I had asked the question is because I have a C85-12F engine in my hangar that has 400 SMOH, and the engine on my Forney F1 has 2200 SMOH on it. The engine swap would be fairly simple and inexpensive compared to an overhaul of the C90. Do you think that there would be much of a performance difference with the plane with the 5 less HP? On another note, do you know if there is approval basis for installing an O-200 in a Forney F1 and do a step up?<<<<< Stan, I'm not an expert and there are experts here on the list who will, I hope weigh in. >From talk I've heard over the years, the FAA is usually not too difficult about engine power changes unless they are too extreme, i.e. putting a much more powerful engine in a plane originally certified much lower. I heard an FAA rule of thumb, once, and my memory on it is vague - 130% of original might be that number. Changing from a C-90 to a C-85 might be frowned upon by them since you are making the plane less capable. But, you could point out that all the C, CD, D, E, & G planes, structurally almost identical, had C-75 or C85. Before you turn a wrench, you'd want to have your AI write up the form 337, submit it and get it signed off. It might not get approved. But going up in horsepower to an O-200 is a smaller change for your plane than it is for the many Ercoupes on which that change has been approved. Experts! Am I remembering right that the C-90 and O-200 share the same engine mount and that it's different from the ones used by the C-85 and before? I'm thinking that moving down to a C-85 would be a big cut to your resale value while moving up to an O-200 would increase it some. But, you already have the C-85 so cash out of pocket is a big deal. Maybe you could change a 400 hour C-85 and a run out C-90 for a freshly overhauled O-200. Let's see what advice shakes out of the tree. Ed Burkhead http://edburkhead.com ed -at- edburkhead???.com (change -at- to @ and remove "???")
