Re: angle fire or not to ange fire that is the question
when the slant head was first brought out, i remember seeing somewhere that it was designed for bikes with limited space, where a straight-plug wouldn't fit.
soon after that, someone got the idea that they'd claim "better performance" and the myth began, and that's about all that's available in new motors.
in my experience building really fast bikes, the straight plug head is the way to go.
i've built motors with all the same mods, and the slant heads aren't as fast, plain and simple.
they're also more prone to warpage, as they don't have a properly designed squish band, causing uneven heating, and they're usually a thinner head, too, providing less cooling and structural integrety.
my advice, if it fits, (and you can still find one,) get a straight plug head.