the other day i was going up a hill at a low rpm and i heard a popping out of the carburetor. i than pull the valve cover off and it broke a screw in stud. i replaced it and put it back together after checking everything. again today i was backin up a hill same thing happened and the stud broke and on the valve next to it it bent the pushrod. what could this be it has sportsman II heads the springs are not coil binding. it has a lunati voodoo cam and it is set dot to dot on timing chain. it also has the correct installed height and 1.5 ratio stock rocker arms. p.s the stud breaks in the same spot where the threads start.