Nitro makes power. But the question is why. Partly due to it's ability to burn in heavy fuel/air mixtures. The thing that moves the piston is pressure and mass. If you pick up a can of 65% fuel and compare it with 15% fuel you will notice the 65% is much heavier. When I was flying Formula One, I would break in the engines on 15% before running the 65%. The difference in needle vavle setting was that the needle was turned one full turn out for the 65% compared to the 15%. So a much higher volume of heavier fuel doing the work. It worked out to be around 3 oz. of fuel per minute in a .40.

You generally need to raise the head for the higher nitro. Plugs we used were the K&B 1L plugs, then later the Nelson types. Plugs only last for one flight, so expect $6 to 8 per flight for plugs and fuel. And the piston tends to go away with the slightest of lean run. Deck height become more of an issue with changes in air pressure, temperature and humidity. You have to learn to "read" the plug. It should be shiny wet looking after a good run with slight distortion of the element. If the element pushes in or pulls out the compression is wrong. If it is gone and/or the plug body is dry, you were too lean. If you were way too lean, the black stuff on the side of your fuselage will be a mixture of oil and metel from your piston.

It is better to start off with the head too high and a light load for the prop. With this set-up, the needle will be very broad and easy to set. As you come down on the head, you will find the needle starts to get peaky and hard to set.