All engines are designed to turn up to a specified RPM range. Before we take this conversation any farther, we need to point out that making any modifications to your engine which causes it to rev higher than its designed wide-open throttle speed usually voids the warranty. As a result, most people who want to make their engine faster don’t do so until an engine is already out of warranty (though if money is no object, have at it). The second fact to consider is that manufacturers design their engines and all the parts attached to them with this RPM range in mind. Push past it and there’s a very good chance something – or everything – will break. Catastrophic failure is not an unreasonable expectation and people who strive to make their engine faster need to understand that they may well get a very short period of enjoyment before the spring you put into that engine’s step is completely sprung. The bottom line? Fine tune at your own risk, and understand that the risk is quite significant.