I have a chance to purchase a Webra Speed .55-P5 Heli Engine, Competition AO 1063HC engine. My question is .. Can this heli motor be used in a speed plane.? And if so, what sort of mods would be needed? I have always heard Heli's are faster due to the porting and they have a longer shaft. Is this a problem for a plane, or is there an adapter? Would like to put this in a Phoenix Strega .40. Any help would be appreciated. Thanks,MG

Well I see nobody had stepped up on this one lol. I'm going to advise against it. RPMs do not mean usable power. The average aerobatic helicopter runs a rotor RPM of between 2,000 and 2,200 RPMs. With an average gear ratio of about 9:1 that puts the engine at about 18,000 RPMs. This is pretty much where the engine port timing is set. So far this sounds great, 18,000 RPMs WOW!! OK the down side, to get the heli engine into it's high RPM powerband, you would have to run about a 8.5X7.5 prop. Now put that on an airplane with aveage drag and the end result would be an airplane that makes plenty noise but dosen't go anywhere. The airplane just wouldn't get going fast enough to unload the engine/prop combination enough to get the engine into the meat of the powerband. You could put on a smaller prop to get the RPMs into the powrband but then you wouldn't have enough prop to overvome the drag of the airplane.

If peak power is developed at 18k that is not radical timing. I would call that peppy sport timing. Such an engine should have no trouble spinning a 9-7 APC up towards 17k and that will pull fine. A West .50 is a little higher timed yet, and will spin a 9-6 APC at 20k, which pulls hard on the ground and a pitch speed close to 120mph.

The major concern I have heard with heli engines, apart from shaft adapter issues, is that the 2-needle carbs are set up to run relatively rich through the midrange.

I disagree....... bvm 96 ducted fan on 40% nitro in a 60 inch stiletto
mustang better than 204 mph - radar, eagletree pitot and gps verified.

OK thats almost double the displacement on an airplane with only 6" more span. I stand by my statements. A high RPMengine swinging a small prop installed in a draggy airplane is not going to go fast. Now if one was to put that engine in a Mantney models Q40 kit it would be a screamer. Imagine if someone suggested a Ferrari engine in an SUV.

My Webra .50GT is a similar engine. I raised the exhaust timing to 180 degrees and set the closing of the intake window in the crank at about 62-64 degrees. It runs a Macs header and pipe.
On a Screamin' Demon Delta the best prop I've found is a 7.5x8 [a cut down 8x8 APC sport prop]. The engine turns it into the low/mid 20s on the ground and the plane does over 170 mph.
The .55 might not get spectacular speed in a Strega but it'll be thrilling to fly and a crowd pleaser in a plane like the Demon. 170 and up on a budget combo is pretty cool.

But a 9" prop is not really a small prop - it will pull a reasonable size airframe. I grounded my old Hots after buzzing the ailerons on a 9-6 on a Picco .40 - tell me that ain't draggy! Below 9" sport props you have to think about the combos a little harder, sure. Spin a 9-7 or 9-8 in the high teens on something like this and it will move out fine, you don't need a pylon racer or paper-thin delta. I am not saying top speed will be in the 150's, no way, but an engine that peaks in the 18-19k range is not as high timed as the example CP points out and I say it can do the job. Whatever.

I guess it depends what you consider fast. When I first jumped into warbird racing I thought the PM Strega would be a good way to go. I still had a couple Webra Q500 engines on hand. I stripped all the covering off, made a new thinner tail section that actually looked like a p-51, took a bay off the root of each wing and recovered silver with invasion stripes. The Webra was turning a 9X7 rev up pylon prop at 16,800 on the ground. End result, the airplane never saw 100mph. One of the guys I race with has a Kyosho Spitfire with a YS 91 heli engine in it and was hoping to run in our gold class. Can't get enough speed out of it. Ihave been running a Rossi .45 in a Wing manufacturing Macchi that tops out at around 130 with an APC 9X7 but when that engine was put on a WMT34 I was gutting passed by the OS.46 powered airplanes. I couldnt get the airplane fast enough to unload the prop so I didn't get into the power band. For someone set on a Strega who wants to go fast I would look around for a good used YS .91ACor a 110. If you really want speed out of it go with the new 115.