Hi all. I am putting together a 60 size Great Planes Matt Chapman Eagle 580 nitro version airplane and am wondering how the engine needs to be installed in order to use a Pitts slimline muffler setup. I am new to these types of planes. The book calls out to use a OS81FS and shows the engine mounted sideways with the exhaust exiting out the right side of the cowl. I am installing my OS91FS for an engine and was wondering if I can install it inverted. Correct me if I am wrong, but isn't that the only way you can use a Pitts style muffler setup? I tried calling Great Planes tech support today, but they are closed. Any help with this would be greatly apprecited. Thanks...

There are Pitts style mufflers for both inverted and side mounting configurations. If it were mine, I would try side mounting the .91 and seeing how the stock exhaust exits out the bottom. Maybe you can do that without buying any sort of aftermarket muffler. You might be able to do the same with the engine inverted too.

My buddy got one of these to turn the muffler to a position that made the engine mounting easier.
http://www.rcuniverse.com/market/item.cfm?itemId=669061
I use the Slimline Pitts muffler on my Saito 180 in a Cap232 mounted on its side and it works very well, and sounds good.