Battery sparked on this noob

[mumbles]

Ok, here's the deal. I upgraded my alt to a 120 amp from eagle on ebay, redid all of my wiring between the alt, junction, starter, battery, and ground, added a chassis to engine ground on the alternator pivot bolt, and added a cable from the alt to the positive battery terminal, all with 2 and 4 ga wires.

Just went to connect the terminals and when I did the ground it gave a good spark, and I heard something pop somewhere else. Looks like it started to melt the points where they touched and the sound may have come from the voltage regulator.

This seems pretty bad, so can anyone help me from blowing myself up?

Thanks.

~bri