is it possible to change a cylinder head equipped with 136mm long valves with shorter valves (130mm)? if ever, what hardware needs to be done also? valve springs, camshaft, etc? in short, i'll be using the same head. only the valves needs to be done if ever. whats the effect on compression ratio, hp & torque band, starting (hot & cold), etc? btw, it's a mitsy 4d56 turbodiesel. i know you guys can shed light on this. thanks