I told the ubuntu installer to use the same /boot drive - it errored, and after i selected another drive (the one it suggested), continued.
Once booted, i only had my old fedora and windows entries in grub.
Run this in a root shell to get ubuntu loaded - note, you must have mounted the ubuntu / partition before executing it.
grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.14.4-200.fc20.x86_64
Found initrd image: /boot/initramfs-3.14.4-200.fc20.x86_64.img
Found linux image: /boot/vmlinuz-3.13.5-200.fc20.x86_64
Found initrd image: /boot/initramfs-3.13.5-200.fc20.x86_64.img
Found linux image: /boot/vmlinuz-3.13.4-200.fc20.x86_64
Found initrd image: /boot/initramfs-3.13.4-200.fc20.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-5a03a6d41476417baf5f18f5d1eec2af
Found initrd image: /boot/initramfs-0-rescue-5a03a6d41476417baf5f18f5d1eec2af.img
Found Windows 8 (loader) on /dev/sda1
Found Ubuntu 14.04 LTS (14.04) on /dev/sda5
done
** tip **
in case you don't like the distro you added, you can remove the partition you installed to, and then run this command again, and the grub entry will be updated accordingly :D