This engine will detonate if you use nitro. When Duke designed this engine during the time when nitromethane was getting expensive, he meant it to be run on Zero nitro. That was his sales pitch. If you were having trouble with transition it was the needle settings. The carb on these are finiky at best and there is a mod to do on the needles which involves modifying the point to help on transition. During this time frame Duke was even recasting heads on the .19,.25 engines to boost compression, allowing the use of Zero nitro.