I am building an Ultra Stick 40 with an OS55 ax.I like the idea of the sideways mount because of the carb to tank height and the exaust pointing down but I have never ran asideways mounted an engine. If you have some experiance with this could you weigh in your opinion, and list some pros and cons of the two different configureations.

Either way will work just fine. Do whichever you feel is best for the application.

No cons to it. To the side or straight up will work just fine either way you install it.

Ken

Sideways installations have some advantages, consider where you want the muffler to end up on your particular plane.

I would also add be sure to balance your plane laterally with all equip either installed or in place(in case you need to move anything around to get balance close befor adding additional weight)especially if you mount engine sideways.add weight to light wingtip.this will ensure that your plane flys true.also mounting sideways will allow installation of tuned pipe down bottom of fuse if ypu want later on.thx.

Anothere very good pro for the sideways mount. thanks

With tuning there isn't much difference, unlike with an inverted install. So pick the one that puts your carb in the right place in relation to your fuel tank height.

I also often use 135 degree mounting to keep the muffler centered, w/o any problems. A nice compromise between inverted and side mounting.

Inverted mount tuning is NOT problematic nor different, but your tuning windows seem to be slightly smaller, as if you were running a lower nitro content fuel... but that's about it.

Hi!
Sideways of course!
Otherwise the carb will be too high!

I have had very good success with sidways mounted engines. I prefer it.

Looks likesideways is the way to go, I do like one feature of the OS 55ax that is not that common. The the low speed needle is on the same side as the high speed needle. This will make adjustments much eaiser, they will be right there on top.