Not familiar with  the 46LA engine. Why do so many choose the ST NVA over the standard OS NVA? I am an old time sport flyer, new to todays type flying.

Thanks, son

Thanks Brett, now for my next question. Why do flyers lower the compression on the 46 LA with washers or removing material. My experience with motorcycle and auto engines is, lower compression is a bad thing. Lower power when climbing during loops and so on. It apparently does not give the 4-2 run much desired. I have read all this being done but haven't found the reason behind it.

David Fretz

I cheated and asked questions too... BUT my advice is to jump to the engine set up side of this forum and a search of OS 20 or LA 25 or LA 46

This has you spending hours of reading to finally conclude=----that many many of these, very still available engines, can run just fine right out of the box with the recommended NVA, Glow plug, Muffler, Prop, and fuel tank set up for a wide variety of models

All the work has been done to determine the appropriate CHOKE area (Venturi vs spray bar diameter)....several vendors will sell you the correct parts for not too much $$

Randy Smith sells OS LA 46s Blue printed
There are guys who swear a metal back plate is mandatory and others that learned how to live with the plastic back-plate

I have been slowly replacing all my old skool 4-2-4 engines (Fox/Enya/K&B/Veco/Johnson) for the slightly more modern OS or ASP/Magnum engines

I fun fly and do not like fiddling with props, tanks, fuel mix.....all the planes converted to ASP or OS start predictably, are set to forum recommended RPMs and fly my quirky- sport fly -NON pattern-without ANY drama....

IMO trying to make a modern High RPM engine behave like a older low RPM engine with a distinctive 4-2-4 break is achievable BUY WHY....you want 4-2-4 buy a NIB Fox 35/40 and have at it....hundreds still for sale.....better yet a $200 Enya .35 new edition if you can find it

With a slightly more modern OS, or clone, You can Stick the right fuel in it, apply the proper low(ER) pitch prop, set launch RPMs and go fly.....too easy

For a good read on a lousy weather day, look up Dirty Dan Rutherford's  very lengthy description of a OS 20 in place of Fox 35 and the now ubiquitous Brett Buck Tune Up (BBTU) a euphemism for leave the damned thing alone and go fly   with OUR recipe of Engine, Fuel, Prop, Tank!

I still have a Fox 35 powered RingMaster...but my others are OS 20 powered....more gooder IMO

I also highly recommend you explore the NOW no longer produced Evo .36 CL engine and if you think a larger plane some day the Randy Smith Magnum .52 is a solid easy engine to set up for something like a SV-11

I am total hack fun flyer but a top end piped Rojett is in my future to just HAVE one

Good to be king
Competing?....electric or Piped RoJett....

    I don't know. The ST NVA is quite inferior to the OS, and unless you do something else,  given the much larger diameter, you lose ~15=20% of your power. As a bonus, you also get to permanently damage your (unobtainable) crankcase by having to drill it out. Leading at least on on-line wise-guy to write forum posts like "Don't drill holes in your new engine", which you would think would be self-evident. the ST also has a long-known issue with vibration, usually it works OK, but sometimes it doesn't unless you really crank down on the collet.

    You also need to get a set of replacement venturis with the larger hole to find the one that you need once you start modifying the engine.

    Brett

I have learned the hard way not to meddle, the OS Needle is actually very good as long as you run a little cyano on the spring to stop the end coming loose. Don't drill the case unless you can't get an OS assembly and then get the advice of someone like Randy Smith who can guide you about venturi choice. As usual Brett is right on the money with his advice.

Thanks guys, sometimes you fall down the rabbit hole reading all these posts.

    Indeed. The first and most important thing to remember is that a lot of the "common knowledge" in stunt, particularly with regard to engines, is either only conditionally true, or not true at all. Compression/head shims is a classic example - changing the compression can have very useful effects in controlling exactly how much power change there is from a 4-stroke to a 2-stroke in 4-2 break engines, and slightly adjusting the operating point on other engines. So, .003-.005-.008 either way can be used to great advantage. Of course that requires a mostly-working system to start with, and the necessary refinement and knowledge to know whether to do that, or go up or down by 2.5% in the nitro, or shave a flat spot on the LE of the prop, or add 1/4" of pitch at the tips of the prop. 1/16" - .080" (which I have seen MANY times, including people whose names you would recognize and should certainly know better) is VASTLY too much of a change unless you have also radically changed something else.

   Same with a lot of other stuff. Particularly with engines. There seems to be some strange school of thought that stunt engines are supposed to be pathetically gutless like they were in 1951. You have the best stunt engines ever available in the history of model airplanes RIGHT NOW, and they are radically better than even 25 years ago. For the last 30 years, there has been no real debate over what works the best, we have had essentially standardized systems with totally complete information about how to set them up that have proven nearly bulletproof, even for the inexperienced - if they just follow the directions. Almost any of them will fly an appropriate airplane in air you can barely stand up in, even if they are a little "off".

   But many beginners, retreads, and even fairly accomplished fliers fall into this world of ancient engines, or current engines designed to run like a particularly weak McCoy 35 redhead, or modified to work the same way. You can easily beat them with a $49 RC economy engine, but no one even tries them as intended, and immediately starts trying to carve them up, or get someone else to carve it up for them. Even if they succeed in coming up with a reliable run, the performance is still terrible.

This is not a new topic:

https://stunthanger.com/smf/engine-set-up-tips/stock-means-stock-and-don't-take-a-drill-to-your-new-engine/msg452220/#msg452220

Brett