My engine is the NGH GT17 and it has the 1/4-32 spark -plug cap. NGH provides and small spring that goes on the very end of the cap to provide some extra tension when you lock it down. The problem was with this little spring in place I could not rotate the cap 1/8 of a turn to lock it down. I contacted Jim at Agape Racing and Hobby and he is sending me a couple more of these springs. He says they do help keeping the cap locked down when while the engine is running. This is the only engine I have that uses this type of cap so I don't know it the EVO 10 has this spring in place.