i have a fiesta 1300cc with an endura-e engine 2001.number 6 push rod keeps jumping off the tappett.i have changed the push rods and rocker shaft & it still jumps off. is it possible it could be a sticky valve or a cam follower. if it is a cam follower do they go in the top or the bottom of the engine.when the engine is running it sounds perfect, when it jumps off you get a popping through the injection box on the top of the engine. can anyone help. cheers