IDK carbide does not cut chrome plating overly well.....most timing changes require not much more then just removing the chrome plating, IMO using a carbide would be next to impossible to get a clean cut when removing as little material as needs to be removed.........A fine diamond bit works well but I Most definitely would never ever recommend using a Dremel for cutting ports..........Dremels are also not a very good choice for cutting ports. because their motors are so amll Dremels need to use excessive RPM to make any power. too much RPM causes vibration and bit runout which makes cutting cleanly very tricky......... I use a Jewelers grade flexible shaft tool which works extremely well....however I still dont think using a carbide works well at all, even in a flexible shaft...