I am after any info I can get on reworking a engine from R/C to stunt I have a HP 40 Silver Star and would like to make it run in a stunt model. I have been told to take a little off the liner and open the squish band up to drop the compression a little.

Or if there is somewhere I can send it to be reworked that would also be good.

Randy Smith, Aero Products, mod'd them years ago.
I have one that he modified, I bought it off a table at the KOI many years ago and it runs great, has for years.
Roger Vizioli

It really doesn't take much to make the Silver Star run for stunt providing it's in good condition and has descent compression.
Replace the Carburetor with .280-.285 venturi and a Super Tiger needle valve assembly obtained from just about any of the aforementioned folks.  I personally would recommend Randy Smith at Aero Products or Jim Lee.
As for the compression a .007 to .010 shim would be all that is needed in any case.  I would probably just try it with the stock head gasket first.
Use an APC 11-4 or or 11.5-4 prop at about 9600 RPM (ground launch) on 65 ft lines.  Should work fine in a 575 to 620 Sq in airplane.
I used one in a Wooley Cobra with that setup and it was great.  Shortened the nose of the Cobra by 1 inch to accomodate the extra engine weight.

Randy Cuberly

Thank you all for the info Much appreciated 

It really doesn't take much to make the Silver Star run for stunt providing it's in good condition and has descent compression.
Replace the Carburetor with .280-.285 venturi and a Super Tiger needle valve assembly obtained from just about any of the aforementioned folks.  I personally would recommend Randy Smith at Aero Products or Jim Lee.
As for the compression a .007 to .010 shim would be all that is needed in any case.  I would probably just try it with the stock head gasket first.
Use an APC 11-4 or or 11.5-4 prop at about 9600 RPM (ground launch) on 65 ft lines.  Should work fine in a 575 to 620 Sq in airplane.
I used one in a Wooley Cobra with that setup and it was great.  Shortened the nose of the Cobra by 1 inch to accomodate the extra engine weight.

Randy Cuberly

Agreed, before you go spending money try a head gasket first.
Good luck  

    Why do you think it won't work as it is?  This engine should run just fine if you put a regular venturi in it.

     Brett

Hi Brett,

I read all the posts and no one asked Craig if he meant a 4-2 run for "Stunt".  If that is his question I would suggest that he simply run it in a wet 2 with a 4" pitch prop and take advantage of the power it can produce in "stock" trim.

BIG Bear
RNMM/AMM

   The Silver Star should do a nice break with no mods if you should want to for some reason. In either case there is no reason to immediately go do rework without trying it first.

     Brett

Hi Brett,

I have 3 Silver Star .40s and two Gold Cup .40s.  One of the GC;s is NIB and the other is well broken in.  I just put new rings in all of them (the NIB GC was shipped from the factory with no ring! LOL!!)

I have never tried to run any of them with a 4-2 break, didn't even think they would do that.   Just 11"-11 1/2" X 4 props and a wet 2 run.  I remember Robby Hunt using a HP .40 with a pipe in his Europa.

Bill

I have bench run the engine with a home made Venturi it has a 7mm hole and a OS needle from a FSR. No Exaust as yet and it runs well rich flat on the bench with a 11 X 4 prop when you put the nose in the air it turns up the revs to warp speed and will not return to a nice wet 4 stroke for about 25 seconds. any thoughts

Send it to Randy!

W.