I decided to change engines to an OS 55 with a pitts style muffler and mount the engine sideways. Was starting to cut the new cowl to fit over the engine when it occurred to me that I won't be able to install the cowl because it won't slip over the cylinder and muffler pipes at the same time. I am too tired to think, so I took some pictures, hoping that somebody has done this already. I figure (in my less than awake state) that I can either cut the entire cowl bottom off (don't really want to do that) and slide it past the pipes. Or, I can remove the muffler mounting screws, cut the proper slot (or holes) in the cowl for the pipes, place the muffler in the cowl, slide the cowl/muffler into place, and then re-install the screws. This would mean that I would have the drill a hole in the top of the cowl to slide the screw through and install the muffler. I think the screw closest to the carb would be close enough that I could just make the carb opening big enough to install the screw. Does this sound about right, or am I just too tired.

It looks like a pretty big chunk will have to be cut from the bottom of that cowl to accommodate the muffler. Pitts mufflers can be a pain when the cowl is a tight fit. I would make a cardboard template of the holes needed for the cylinder head, muffler and needle valve. Make these on pieces of cardboard that are fairly long and take the end back on the fuselage behind the cowl. then remove the muffler or entire engine, put the cowl in place and mark the area to cut through the holes in your template. Then you can just cut the cowl to your marks. I bet you'll have to make the muffler opening quite a bit larger though in order to get it to slide on. Your idea of installing the muffler after the cowl should work too. Just drill a couple holes to access the mounting bolts.

If it were me, I would just cut out a large enough opening in the bottom to slide the cowl over the muffler. On the bottom of the plane, it wont stand out much. You will also want plenty of exit area for the hot air. General rule of thumb being that the air exits should be 3 times as big as the intake.

Yup that doesn't look like a big problem.

Using the aforementioned cardboard technique cut a hole for the cylinder head.

Then cut a "U" shaped area for the Pitts muffler.

The "U" will not be very large and it will also help cool the engine.

To install the cowl you will start by looping the cutout hole over the cylinder head, then getting it past the prop bolt, and then in place.

You may also need a hole or two for the needle adjustments.

On mine, I made a horizontal cut at about middle of the right side, behind the cutaway for the engine. This allows for the cowl to spread enough when you are putting it in place. There will be a small amount of cowl between the cutout for the head and the carb. Be sure to reinforce that section with epoxy and a small dowel like a bamboo stick or wire.

I just noticed that the centerline of the engine does NOT look right.

The markings on the firewall line up with the upper part of the engine retaining tabs ( with the holes ).

The markings should line up with the bottom part of the retaining tabs, which corresponds to the engine centerline.

The engine appears to be too far over to the side closest to it's bottom ( opposite the cylinder head ).

The engine centerline needs to be to port (left) side of the firewall. The built in right thrust will position the prop at center.

Heh, yes I'm fully cognizant of how thrust lines work.

However his centerline is offset too much.

The engine is not aligned with the marks on the firewall for the engine it seems.

It appears that the engine is too far over.

Check it out. The normal setup for a glow engine on the Pulse is to align the engine centerline with the firewall marks.

The firewall marks are not the firewall centerline, rather they are representative of the proper offset for the engine.

The engine centerline at it's base should align with the firewall marks.

You can see this in detail on the Pulse manual which can be downloaded from Horizon.

It looks like he aligned the engine prop bolt with the centerline instead... not good.

i fitted my SC46 sideways with exhaust underneath.
heres a couple of pics, dont thinks its much help to you as ive just got the one big hole for head and muffler
it does give it a better look

opjose,
You had me a little scared there for a minute. I think the picture fooled you from the bad angle. I had to remove the stock blind nuts, fill the holes, and then install new blind nuts in the correct position. I double checked everything before drilling the holes for the new blind nuts. The motor is installed correctly. Even this picture looks a little off, but the engine drive washer is in the center, 4" from the firewall.

V8mini,
Thanks for the pictures. I am going to have to go to plan "B". In case anybody wants to know, the OS 55 with the bisson muffler will not fit on the Pulse XT 40. At least, there isn't very much cowl left.[X(] Since I did all that work to mount the engine sideways, I am going to have to stick with the stock muffler with an extension on it. Means I will need to order another new cowl, and I will have to figure out a way to grind out some of the interior of the extension. I asked about it in another thread. http://www.rcuniverse.com/forum/m_7171452/tm.htm
Too bad, I really wanted to use the bisson muffler. Guess I will have to buy a plane that can use the bisson muffler. Wait, that means I will need another OS 55!
I really like the way the Pulse XT flys. I was thinking maybe this for a next step up in planes.
http://www.hangar-9.com/Products/Def...ProdID=HAN2650

Any suggestions?

Sorry, I thought you were referencing the firewall centers.

Yeah it looks fine in that picture, and you can see the slight right thrust.

Sorry, the other pics looked like the engine was too far over.