So Pyroak makes for a poor defensive/support option with Celebi on the field.
Offensively, he does have access to Mud Bomb, which allows him to hit Heatran, freeing up his Hidden Power slot to hit dragons with Ice.
Modest with Life Orb will do 98% minimum to a 0/0 Heatran. Of course, LO seems counter-intuitive on a slow, bulky creature like Pyroak, but without the boost, the damage is more like 75-88%.
It isn't much, but it's something that allows him to compete with Celebi's Earth Power option when taking into account his Fire STAB.
If you're going for a Specs set, note that Mud Bomb isn't compatible with Leaf Storm.