ORIGINAL: ululi1970

I am looking for a 4-stroke engine to power a small bipe. The complete airframe minus the engine weighs 42 oz.
Right now it has a Magnum .30 4-stroke, which weighs 10 oz and balances the plane just right. However, it is severely under powered. It can't pull it through a loop even
diving before entering the loop to pick up speed, and flies dangerously slow. I am not sure if this is a problem with the engine it came with (swings a 9x6 at about 10,800 rpm oon 10% nitro), or this type of engine
is not the right one..
I think I would like to get about 45 oz of thrust (90% thrust to weight ratio).
Is there a 4-stroke engine in the 10 oz range that can deliver 45 oz of thrust with props in the range 9' to 10'?

Thank you
Alberto