I was wondering who might be able to retune the LA46 to make it a good 4-2-4 motor. Thats the style I like better than the high rev low pitch style.

ADD A HEAD SHIM?

I mostly ran mine on a MAC's Muffler setup, but one Labor Day, I flew half a dozen flights with a full 12-5 APC and a tube muffler that is probably a Big Art product. The 12-5 was a bit too much, but cut to 11.5, it would have been sweet (FWIW, my Dirt/Aldrich tune ST G.51 also doesn't like the full 12-5, but trimmed to 11.5, it's very good). While I liked the 12-5 on the .46LA, my test subject (Humongus) didn't like flying that slow, and the fuel tank wasn't big enough for the 4-2-4 run. I'll try it again, maybe in a Profile Cardinal with a 6 oz. tank.  Steve

Hi, Will - I have not done anything with the LA for three years but, if memory serves, the venturi ID was .290. That, in conjunction with the OS NVA (.156 OD) really did the trick.
By the way, the venturi was my own design, not thee one supplied by OS.

Also, I ran the plastic backplate without any problems. I simply removed the backplate gasket (as I do in ALL my engines) and sealed it with Anaerobic Gasket Maker - Loctite 51817.

Bob Z.

Thanks Bob,
It sounds like I'm in the ballpark on my 46 with the ST51 NVA.  Now for spring!  By the way, I also, (though they say ya don't have to,) use the same gasket goody on my tuned pipe headers.  Good stuff!
Blessings,
Will

"""Hi, Will - I have not done anything with the LA for three years but, if memory serves, the venturi ID was .290. That, in conjunction with the OS NVA (.156 OD) really did the trick.
By the way, the venturi was my own design, not thee one supplied by OS.""""


HI Bob

Isn't the OS  NVA  a  .136 diameter?  This has been one of the problems people have setting up these engines
Most All of the standard size spray bars we used were .157 OD. The older  OS  types from the 35  and  40s used to be .157 same as the Super Tigers and  PA , KK  etc.   When OS made the newer FPs  they went to the  small NVA diameter. People were used to running  a  .285 venturie in these type engines, but when you put in a .135 NVA  they .285 venturie  acts  and  is  Much MUCH  bigger, helping  add  to teh  "runaway" problem

Regards
Randy

Hi, Randy - the one I used was a very old one. From the 60s as I recall.
Same diameter as the ST.

I have not used the newer ones.

Bob Z.

HI Bob

You most likley  used one from the older  FSRs ,   40 or 45, good NVA , It keeps the same  area inside the venturie that people are  used to  using in their motors.   Too bad OS  doesn't make them any longer or kept them at least the same size when they went to teh FP series

Regards
Randy

thanks for correcting that Leo,,

hey guys, and to think Leo judges me most of the time,, heck now I want to go back and readd my scoresheets,, lol,,