Sig Chipmunk Engine selection

[dave siegler]

I have a lot of good choices

1) Big Art G21 ST 46 used, a gift, has run I have not
2) Fox 40 silver fox I think.  Ran on bench runs strong
3) Several FP40's well broken in and some un run, one with stunt timing
4) LA 46, used, never run

I am leaning toward the LA FP 40/ 46.  I can swap if I have an issue.

Oh the wood in this kit is super hard. 

[Tim Wescott]

If your goal is nostalgia, go with the ST 46.

I'd build it so that I could change back and forth between an FP 40 or the LA 46, then if I had time I'd try all three.  The tuning for each engine is going to be individual, and the tuning for the "stunt timing" FP 40 is going to be markedly different than the unmolested FP 40 or LA 46.  If you optimize for one and then use that combination on the other two, they'll run like crap.

If I were going to build for just one of those, it'd be the unmolested FP -- but the only reason not to use the LA is that it's a bit big for that airframe.  It'll tone down just fine, though -- it's the one engine of all of those that I can say you'll definitely have success.

Use a stock OS E3030 muffler, or a muffler from a Tower 40 if you can get it (the Tower 40 muffler seems to work the same, and it's lighter).  I haven't tried a tongue muffler, but when I look at the guys who are sorta-winning without tuned pipes, they're either running engines like the Retro, or they're running LA46's with stock mufflers -- so I take my guidance from them.

(Or sell all of those engines to enthusiasts and use the money as a down payment on a PA -- but I digress).

[Gary Dowler]

Tim is probably on to the right idea, but I’d suggest a little harder look at the LA.  It’s just such a proven, reliable, repeatable stunt engine. 
It is a little “big” for this, but in his letter to another flier (can be located here on SH) Dave Fitzgerald state’s that the 46LA would do just fine, with a few changes to the kit.

Any of them will work, but I’m a fan of stock, unmolested engines.  Still going to agree with Tim, with a little preference given to the 46LA.

Gary

[Skip Chernoff]

La 46 for sure,but be prepared to add some tail weight if stock muffler is used....IMHO