When I dropped a savage .21 into my maximum st, I had to make a custom manifold for it because the exhaust pipe would have pointed side to side on my truck instead of front to back because the original duratrax engine had exhaust output in the side of the engine, where this engine's exhaust output is on the back of it. So I bought a few 1/2" copper fittings, one elbow and one extension and combined it with the existing savage manifold to get the exhaust to point where I want it to. It fits good and it hasn't costed me any power. Surprisingly these copper pieces fit so snugly together and to the existing manifold that there was no need to sodder them together. I can upload a pic of what I'm talking about it you want.