Hello, Robin, we had an opportunity to try a ST 40 GS reworked by Byron Barker(CF Slattery Co). Outstanding 4/2/4 style run, with nice power, easy starting and easy on fuel...just under 4 ounces for a pattern. Looks like he hemi's the head, better venturi and ST nva, and angles the ports slightly.  I'm far from an "engine man", so you might contact him for better info. We've seen good success with Byron's engine rework.

I have a ST GS .40 that I'm using on a Brodak P-40.  I installed a ST .51  C/L venturi and one of Randy Smith's NVA's.  Other than that, it's stock. 

I'm pretty happy with the way it performs.  The engine has a lot of power.  After trying several props, I settled on an APC 12/4.  Had some trouble with the engine run when the plane was inverted but adding muffler pressure solved that problem.  I don't get a strong 4/2 break with this set up but the engine run is smooth and consistant.  Did I mention it has a LOT of power?  Quite a bit more than my ST GS .51 control line version, in my opinion. Makes me wonder if converting a ST GS .51 RC engine to control line use might not be a bad idea.  I'm somewhat disappointed with the power my ST GS .51 C/L (factory stock) engine offers.

I neglected to mention that I added a Big Art's tube muffler to the ST engines.  The factory muffler looks like it would be better suited for use on on a lawn mower!

Joe

Hello Robin,

The tank I'm using on the P-40 with the ST GS .40 is a Sullivan, 4 oz., plastic clunk tank.  I've had good luck with this tank set up and use them on most of my planes.  The pressure line from the muffler goes to the tank overflow tube which is positioned (bent up then straight out the stopper about 1/2") to near the top of the tank. Fuel fill tube end is near (bent down, opposite of the overflow and straight out1/2") the bottom of the tank.  Just curve the flexible fuel fill line and the overflow line up and down. I secure the fill line on profile planes with a strap mounted on the fuselage. The overflow just plugs on to the pressure fitting on the muffler.  The fuel supply tube goes into the tank 1/2" and extends out of the stopper 1/2" with the line going to the engine.  You'll need to make the fuel supply tube about 1 & 1/2" long.  I use a sintered bronze clunk.  Use the flexible fuel line supplied with the tank for the clunk connection.  I have found this type clunk reduces air bubbles in the feed line and acts as a filter. Make sure the clunk is close to the back of the tank but not up against the tank.  It should move freely in all directions. I don't like using the wire supplied with the Sullivan tanks for securing the flexible fuel lines to the tubing.  It has a tendency to cut through the soft line.  I cut off some 1/8" long pieces of the clunk fuel line supplied (there's more than needed) and slip these pieces over the ends of a needle nose plier.  Spread the plier open enough to allow the piece of tubing to slide over the lines.  Slip the lines over the tank fittings and slide the small tubing over the connection.  It will hold firmly without cutting the flexible line.

Probably more information than you wanted but thought I would explain the whole tank set up in hopes that it might be of some help.

Good luck with everything and let us know how the ST .40 works out for you.  I'm happy with mine.

Regards,

Joe