When you run the engine or fly the airplane, plug the over flow tube, and then put a short piece of fuel line with a 45 degree cut in one end on the fill tube. Make sure the cut angle faces the prop wash. That will cut your siphoning problems and actually pressurize your tank just a bit. Have fun with the "big" engine!
  Type at you later,
   Dan McEntee

   A couple more things I thought of after my last post. Since you had to tinker with the spray bar assembly already and have an idea of what is going on there, you may want to take it out and put the needle valve on the other (inboard) side. This will let the fuel line make a nice straight run from the tank to the spray bar fitting. When you put the spray bar in, try to have the hole at a slight angle towards the back of the venturi. Kind of where it is just out of site if you were looking down the venturi. This is the area where it will get the best fuel draw. Make sure that you get the nut secure. I find that a couple of nut drivers, one for each side, makes this easier. Jim Lee makes some neat little socket wrenches for this chore also.
  With the tank that you have, you will notice that the engine will pick up speed as the tank runs down,more noticeably at the last 1/4 tank probably. This is because it is a normally vented tank, and as the tank level goes down, there will be a bit of a vacuum left behind in the tank that will decrease fuel flow, thus leaning out the engine. If you had a muffler, that would minimize the affect some what. The cure for that is a uniflow tank, which can be made from a plastic tank, or made from tin stock, and it doesn't have be a clunk style tank. Search uniflow tank here on the list and you will find volumes on the subject.
   Again, have fun with the "big" engine. You will find that they act a lot like the Cox, and can be easier to get good steady runs from them. I imagine a 7-4 to 8-4 prop will be what you want for the engine, and given that Enyas can take a while to break in, I would run at least a quart of fuel through on the bench with the 7-4 prop.
   Type at you later,
   Dan McEntee

Ok. So just a little update. I did look at switching the needle to the other side, but, I would then have my hand in the exhaust, so I did abandon that idea till I can make a tongue muffler for it. Number two. I did fill the tank, immediately plug the overflow line. I then made a 45 degree cut on a couple of pieces to put on top of the fill tube. It fired right up with no problems and ran just fine. Just that it still had the tendency to pull fuel out of the tank and spray it back all over my floor. I will either look into uniflow and or clunk tank now. For some crazy reason too, it would now only run for about 1 - 1 1/2 minutes with the mods and befor it was closer to 2 1/2 - 3 minutes. I wanted to run it again today, BUT, we woke up here to white stuff falling from the sky and 2+ inches all on the ground. I did cut my grass twice already in the past couple weeks....

Do a search on balloon tanks. End of siphoning problems!   

Really. I do not need to search for them, as I use them on a couple of my Cox engines. I had just never thought of using one on anything bigger. Well, it now looks like my problem may be solved. Testing to come later this week! Thank you Larry.

Why don't you plug the fill line and put a 45deg cut tube on overflow line?

Aki

Because I did not think of that. I had plugged the overflow and put a 45 degree cut tube on the fill line. Well, if the weather gets nicer here soon, I will try that method too before I unmount it in favor of a balloon tank. I got nothing to lose. Thanks.