I have recently rediscovered this hobby and got back flying after a 2 year hiatus (college and spending nearly 2 years worth of grass mowing money on a midwest extra 300s and being to scared to fly it)

Well I have an almost 4-5 year old morris knife thats never been crashed. The stab is crocked by a few degrees and the pull pull linkages need work, and I'm thinking about taking it off the moth-balls.

I was thinking of doing a recovering job and while I'm at it fix up what 3 years of crazy funflying does to an airframe and my rushed building. I have a .91 os 4 stroker and got the crazy idea to mabye put this engine on this plane. do you guys foresee and disasters with this setup?
The plane was built when I had no planes in the air so parts of it are a little rushed (the center section is a disater area of wires and balsa).

I was also thinking of relocating some of the servos to unclutter the center section. Move the aileron servoes out a bay or two on some bass rails or something mabye move the elevator servo out back infront of the stab.
I might just pull out the plans and rebuild a whole new airframe from them its not to hard I just regret not building the plane straight enough to do what I wanted to do with it the first time (I never hovered even tho back then hovering and tourqe rolling where basically all the 3d you did). However no matter how squirrly it flew it was always a fun plane.

Anyways what are your opinions?

I think an OS91 is not only a waste but it's gonna take away from the lightness you want in a profile plane. Sure it will fly the plane but your going to increase the wing loading so much it's going to take away from the fun factor. A Saito 72 is a perfect match weighing in at only 16.6oz.

I acually first flew the plane with a .46 and a long tuned pipe which is probably a similar weight to a .91

Either your 46 was extremely heavy, or the long pipe was made from lead, or your scales are broken. I can't understand how a 46 with a header and tune pipe can come anywhere close to the weight of a 91! I agree with the above statement of Wreckman2. Don't waste your time putting a 91 on a 40-size Fun-Fly. As stated, it will fly, though the torque of the 91 will probably break the fuse eventually. The wing loading will be so high that its flight characteristics will absolutely SUCK!!!!. Too much power has its penalties. You'll have to add so much weight to the tail just to get it to fly correctly, or anything close, that the wing loading will just be way too high. I hear of people putting a 91 4-stroke on 40-size Fun-Flys and claiming that they fly great. Then that few that you can convince to try a good BB 40 -50 on the same plane come back a state that they can't believe how much better the same aircraft flies with the lighter motor. How much more it is acrobatic, recovers so much better, etc. I've convinced a couple of my customers in changing to a smaller engine that they still thank me for that suggestion to this day. If the 91 is the only engine that you have available for this aircraft, either trade the aircraft for something that is more suitable for the 91, or trade the 91 for a good BB 40 - 50 2C or a 60 -70 4C. You won't be sorry. You will be if you put that 91 4C on that Fun-Fly!
My 2 cents!
Kevin

Ok you guys convinced me I'll make sure to make my repairs lightweight and continue using my .46 sf.

anyone have an experience with one of those tower mufflers and a .46 sf engine? (older version of OS engines before the FX and LA)

Kallikrates, Do yourself a favor and buy a MVVS .40 exhaust system. I have Knife and Spinsaion with an OS46SF and the MVVS exhaust and this combonation is unbeatable!!! You will have to file (elongate) the holes in the header but it is only a small amount on each side.

With this combo you have instantaneous throttle response. :thumbup:

Kevin

I run the tower mufflers on my OS 46, Irvine and TT motors... Really helps give a little more in terms of performance.... Just make sure you either pop rivet the middle tube to the two cast ends or glue it together with hi-temp silicon and locktite the thru bolt..... Works great... good for 500 - 750 rpm and the throttle response is a little more crisp.