Our recent swap shop purchase landed me this little Nelson.  This is my first Nelson so I am unfamiliar with what
they have produced over the years.  It looks like a .15 but I have no idea when it might have been made nor it's
original use...Like speed or combat...Whatever it was I will use it on a c/l plane of some sort.  What I want to
know is...does it need a pipe?..or just straight. Anyone care to enlighten?

Thanks Paul....just so happens I have a .15 carrier project on the bench...what would you suggest for nitro/oil content to make this
little jewel purr?  I also have a Perky in kit form still and that sounds like a match too.  I'll have to tinker around to fit a carb but that
shouldn't be too hard.  If you get a wild hair to let one of your .15's go let me know.  Looks like I have two planes and only one engine. 
Sounds like the 60's again when I had to swap engines around to fly what I had.  Thanks for the response.

Nelsons are why the FAI invoked the 10% rule.  It was fun while it lasted.

     I purchased a Nelson .15 from Henry around 5 years ago with side exhaust. At the time I was running a RJL Conquest in my .15 carrier planes. I was making the .70mph OK but was concerned with how long the Conquest would last (especially the lower end of the connecting rod) and as they had the same mounting dimensions and knowing the longevity of the Nelson it was my choice.
     After doing some testing with the props (APC 7/4) fuel (SIG 10%) these are the numbers.
          RJL Conquest turned 19.5 to 19.7k
          Nelson .15 turned 22.3 to 22.8k
     On the conquest I used the stock carbureter that came with it which looked like a Perry (but I don't think it was) and on the Nelson I used a Perry # 2400 that had the ID shimmed down to .220 and the OD filed down to .500. The Nelson came with a beautiful little carburetter that had a ID of .295 (it had a large spray bar) but as I have always been fond of the Perry's and the supplied carburetor (with the Nelson) had such a large ID I used the Perry.
     So far I have not used the Nelson in a carrier plane because I got a couple of MVVS reverse rotaion engines at about the same time so am using one of them on my current .15 carrier planes. The MVVS "just makes it into the very low 70s" so some day I will probably build a plane for the Nelson. That Nelson is so pretty I just like to get it out and look at it sometimes and that is only surpassed when I take it out and run it, man it sounds so great.
     Another thing I have found with my Nelson engines is that they run faster and faster over the years. When I started running the heavy case Nelson .36 in profile back in the mid 90s I was turning the HS portion of the flight in the mid 20s and now with the same engine that has never been touched since new it is turning as fast as the high 17s and almost always in the very low 18s. This is done with 10%fuel and the ultra thrust muffler with a APC 9/6 prop. I cant say enough good things about the Nelson engines I use. eric

My rear-intake, rear-exhaust Nelsonis went about 112 mph on 40% nitro, as I remember.  They'd go even faster on crazier fuel.  He says he can't make anything to compete with the Russian engines with the current rules. 

Re reply 3 = Maybe  File or machine down the OS Carb spigot dia.

Henry might not talk to you if you take a black and decker to his engine.

Lacking a 'machine ' a fine B file counting strokes and rotating carb on flat solid surface ,
if the change is a mm or less its not difficult to maintain circularity.

Some of the OS 21 Marine carbs are high duty contraptions .

Thanks for the responses Paul.....and all those who took the time to reply. The Nelson is now
in my new Perky that will fly in a week or two when the weather clears up.  Buz Johnson was
here for this years SMS in Perry last weekend and has suggested I come to the April Speed
event in Florida and race it...so that's the plan now.   My .15 Carrier Wildcat will get one of
my Supertigre .15's that is already equipped with a carb or an FP .15 w/carb.