These are genuine Toyota so massive quality The should be fine without machine work on stock cams but your engineer would need to check for coil bind as bring stiffer and thicker they will bind sooner than stock. But that is no different than the difference between 4efe and 4efte (thicker and bind sooner) Only reAson I'm not running them is I'm running speedvision billets, and I don't fancy putting any extra pressure on them! Phil