OS FP40 RC to C/L conversion

For control line I read where Randy Smith, a highly acclaimed CL engine tuner says the .35fp venturi is best for the .40fp. I believe the NV(spraybar and needle) are the same part in .25 thru .40. I buy mine at Omnimodels' eBay store. The ,40 is not as user friendly as the sweet .35, but the venturi change might solve its runaway tendency. I'm 99% sure the Tower will fit, however I don't know if it's steel or ABN.

I've only flown my .40fp one time and it ran fine on 10/22 Powermaster, my fuel of choice. Next in line is Sig 10/20 plus another dose of castor to make the total oil 22%. I've never met an FP I didn't love.
Rusty

Mark beat me to it, but I'll post my thoughts anyway. He knows more than I do about these engines.

Mark Boesen wrote:The .40FP is/was a very popular stunt engine and can be made to run very well. How much is a new piston/sleeve going to cost you? If its a high time engine you might need a conrod as well? If your trying to get by cheep, you might shop feebay for a nice used FP. I wouldn't try to set it up for a 2-4-2, instead use a 11.25x4 apc and go fly, i think for this set up a remote needle would be fine, you may also want to buy a couple head gaskets...i'd surf Stuka Stunt or any Control line forum for more info.

http://www.ebay.com/dsc/Airplanes-Helicopters-/34056/i.html?_nkw=os+40+fp&_frs=1

https://www.rsmdistribution.com/index-2.htm

Yeah that's what I've heard It still runs btw it just cuts out after it warms up, a sure sign of the P/S worn out (Has very little pop too once warm). The rod is ok I pulled it apart and checked it before taking the pic. It's been religiously run on a castor diet and when I was still flying it, I always set it a little on the rich side (ie) peaked it out then backed it off about 3 or 4 clicks. It flew for years powering my RC trainer plane (Goldburg Eagle63) that I used to use for the club. As far as pricing a new P/S set, I haven't looked too much as of yet. Last time I looked they were around 35 dollars for the stock OS ABN set but that was years ago. I'm interested in trying a true ABC setup  which is why I asked about the tower 40. (Bandit)

lol, IDK, my Magnum is only 20% done after 10 years, you're flying one! When i was flying stunt, half or better were flying 40fp's....i also can't tell you how much time i spent trying to set one up for a 2-4-2 break, even learning how to re-port the sleeve. I finally stumbled onto just running them in a rich 2 cycle, about the same time many others did, thats why i suggested Stuka Stunt or Stunt Hanger, i think the hot set-up is something like a .265-.270 venturi, like Rusty was saying about a .35 size, and big prop(APC) with smaller pitch, 12x4 cut down to 11.25

Why would you worry about a ABC vs. ABN? How may hours do you have on your FP?

I'd also look into a .46LA

http://www.ebay.com/bhp/os-46-la

Mark Boesen wrote:lol, IDK, my Magnum is only 20% done after 10 years, you're flying one! When i was flying stunt, half or better were flying 40fp's....i also can't tell you how much time i spent trying to set one up for a 2-4-2 break, even learning how to re-port the sleeve. I finally stumbled onto just running them in a rich 2 cycle, about the same time many others did, thats why i suggested Stuka Stunt or Stunt Hanger, i think the hot set-up is something like a .265-.270 venturi, like Rusty was saying about a .35 size, and big prop(APC) with smaller pitch, 12x4 cut down to 11.25

Why would you worry about a ABC vs. ABN? How may hours do you have on your FP?  

I'd also look into a .46LA

http://www.ebay.com/bhp/os-46-la

Just want to try it and how many hours? too many to remember lol. It's been a real reliable engine and has trained may RC pilots and I would like to resurrect it and put in a new home (Bandit)

A lot of people think that ABC is the way to go and ABN is junk...but your FP seemed to do ok.

ABC defently does have it's advantages. lean run resistance for one. IMO ABN (Aluminum, Brass, Nickel) there is nothing wrong with it provided that the plating is applied properly if not, as with some of the cheaper manufacturers, it peels like a banana. Some of the early OS ABN sleeves had that issue if low quality fuels were used. First signs of peeling started around the ports and once it began, it spread fast. Also I believe that the FP has better lean run resistance than the LA due to the FP having a real bronze crank bushing cast into the crankcase whereas in the LA the crank rides in plain aluminum. I've never had any issues though. It's all in how you care for your engine feed it good quality fuel and it will be happy for a LONG time. (Bandit)

My club runs them exclusively. I have 3 of them with the Tower .40 assembly in them. Essentially it doesn't do anything more in terms of a power advantage. The Tower .40 though does in my opinion run stronger than the stock FP.40. The Tower .40 also uses a slightly different head combustion chamber than the FP. Many of my Fp's have the heads hemi'd to allow for better tuning due to it taming the engine. The FP.40 was also made in a iron piston version. Yours appears to be the ABN. However it becomes easier to detect my findings by seeing the exhaust side. Run with the proper fuel Powermaster GMA 5/22 the engine will never wear out in your lifetime using the stock assembly. The problem with the FP is it has a very bad attitude at times. Vibrations on a poor airframe will relinquish the run into a frustrating day. Typically the engine starts out breaking nice back and forth in and out of a wet 2 cycle and then all of a sudden its off to the races with a screaming lean run to the end. The stock venturi o-ring is very susceptible to leaking due to being compressed over time which sometimes requires doubling it or using the proper RTV on it. Air leaks in tanks and the venturi assembly will cause nothing but a headache. Be certain it's installed when the new venturi goes in. A properly fit venturi might require a Quick grip clamp to squeeze down the venturi to insert the spraybar assembly due to thumb pressure not being enough.

Here's the solution to some of those problems. Seeing your on a quest to find the proper venturi, this is also relative. A stock LA .25 venturi is about .265". Personally that's too small and while the economy will be greatly improved, the power will be way down. .280" is too large so keeping your venturi size about .270"-.273" works well at least at sea level. Your elevation is under 600 ft so therefore I see your setup being similar to mine aside from the temperature differences in the hotter months. Cowling this engine in can lead to other problems and requires a bit of finesse to provide proper cooling. This allows enough fuel to keep the engine out of the overheating stage triggering the engine to runaway. Adding a additional stock OS head gasket .010" is also in order as it will lower the compression and soften the engine transition from a 4 cycle to a 2 when the nose is pointed up but will leave plenty of power to keep things moving along nicely without making the plane go too fast.

To answer your question, yes a stock LA assembly will work . I would use the LA.46 venturi and the stock up front OS needle. Lately, I've found the OS assemblies to be very crappy and the threads are either too loose or the plating is done poorly making for a rough assembly. Remember the spraybar size is relative to your venturi throat size. Randy Smith as Rusty mentioned provides the best needles on the planet. However, Randy is out of needles currently.

Running the proper plug which is a hot plug like the Enya #3 or a Thunderbolt r/c long. Stock OS plugs are ok but they do have a different reach than the above so therefore you will receive a different or slightly different run from them  due to a slight timing change.

Prop is a major factor and seeing that the FP.40 is a high timed engines it wants to run fast so holding it back only results in overheating. One prop we found that gives you a wide choice of airframes to use is the AP 10.5x4.5 which is a free flight prop. This prop is a bit pricy almost nearing $4.50 when compared to most sport props they offer at 1/2 the cost.

Mufflers are something else to consider. Take the stock muffler and pretend like you don't own it. It's too heavy, not to mention too restrictive. It can somewhat be made to work by taking all the guts out of it like the cone inside. Personally, the Randy Smith tongue muffler is the solution. The Randy muffler comes with holes too small, open them up to the next size drill bit which is 3/32". If this becomes problematic open only one row of holes up to 7/64" and try again. This engine heavily depends on not having heat trapped and a free flowing muffler is in order. Ken

Ken Cook wrote:My club runs them exclusively. I have 3 of them with the Tower .40 assembly in them. Essentially it doesn't do anything more in terms of a power advantage. The Tower .40 though does in my opinion run stronger than the stock FP.40. The Tower .40 also uses a slightly different head combustion chamber than the FP. Many of my Fp's have the heads hemi'd to allow for better tuning due to it taming the engine. The FP.40 was also made in a iron piston version. Yours appears to be the ABN. However it becomes easier to detect my findings by seeing the exhaust side. Run with the proper fuel Powermaster GMA 5/22 the engine will never wear out in your lifetime using the stock assembly. The problem with the FP is it has a very bad attitude at times. Vibrations on a poor airframe will relinquish the run into a frustrating day. Typically the engine starts out breaking nice back and forth in and out of a wet 2 cycle and then all of a sudden its off to the races with a screaming lean run to the end. The stock venturi o-ring is very susceptible to leaking due to being compressed over time which sometimes requires doubling it or using the proper RTV on it. Air leaks in tanks and the venturi assembly will cause nothing but a headache. Be certain it's installed when the new venturi goes in. A properly fit venturi might require a Quick grip clamp to squeeze down the venturi to insert the spraybar assembly due to thumb pressure not being enough.

Here's the solution to some of those problems. Seeing your on a quest to find the proper venturi, this is also relative. A stock LA .25 venturi is about .265". Personally that's too small and while the economy will be greatly improved, the power will be way down. .280" is too large so keeping your venturi size about .270"-.273" works well at least at sea level. Your elevation is under 600 ft so therefore I see your setup being similar to mine aside from the temperature differences in the hotter months. Cowling this engine in can lead to other problems and requires a bit of finesse to provide proper cooling. This allows enough fuel to keep the engine out of the overheating stage triggering the engine to runaway. Adding a additional stock OS head gasket .010" is also in order as it will lower the compression and soften the engine transition from a 4 cycle to a 2 when the nose is pointed up but will leave plenty of power to keep things moving along nicely without making the plane go too fast.

To answer your question, yes a stock LA assembly will work . I would use the LA.46 venturi and the stock up front OS needle. Lately, I've found the OS assemblies to be very crappy and the threads are either too loose or the plating is done poorly making for a rough assembly. Remember the spraybar size is relative to your venturi throat size. Randy Smith as Rusty mentioned provides the best needles on the planet. However, Randy is out of needles currently.

Running the proper plug which is a hot plug like the Enya #3 or a Thunderbolt r/c long. Stock OS plugs are ok but they do have a different reach than the above so therefore you will receive a different or slightly different run from them  due to a slight timing change.

Prop is a major factor and seeing that the FP.40 is a high timed engines it wants to run fast so holding it back only results in overheating. One prop we found that gives you a wide choice of airframes to use is the AP 10.5x4.5 which is a free flight prop. This prop is a bit pricy almost nearing $4.50 when compared to most sport props they offer at 1/2 the cost.

Mufflers are something else to consider. Take the stock muffler and pretend like you don't own it. It's too heavy, not to mention too restrictive. It can somewhat be made to work by taking all the guts out of it like the cone inside. Personally, the Randy Smith tongue muffler is the solution. The Randy muffler comes with holes too small, open them up to the next size drill bit which is 3/32". If this becomes problematic open only one row of holes up to 7/64" and try again. This engine heavily depends on not having heat trapped and a free flowing muffler is in order. Ken

Cool thanks for the advice man and yup you are correct, it is the ABN version.
I plan on using the MC59 since it too is a hot plug and I still have quite a few of them. I just about exclusively ran it on them during it's RC career and it still has a fairly new one in it. I plan on mounting it on a profile model BTW (Bandit)