If the engine is already mounted we need to know what position it is in. If it is 90 degrees like DB said then a pitts style muffler is what you need . Bisson and Slimline are 2 good brands to get.

If the engine is straight up or upside down then you need a muffler for a verticle application. Slimline and J'tech have mufflers for this. If you have not mounted the engine, give DB's suggestions some serious thought. One of them should get you fixed up right. Good luck.

Mark Shuman