Any one that comment about this, I ran my <font color="#000000">OS</font> 91 FX with 14X6 <font color="#000000">prop</font> to get 11 krpm +, instead of 16x8 that I was using before (8 krpm). Now I heard a metal knock, too metalic, at the beginning was somekinf less lowder and less frquent, at the end I decided to land after 3 or 4 mins of flying to chech id muffler or something was loose. Nothing all in the right place.

Have you heard something simiar in your engines? colud be some called "Knocking" due to the fuel?? Thanks in advise for uour comments and advise. <span class="info"></span>