just caught the biggest Eevee i've ever seen ... 813

If you haven't used the naming trick on Eevee you can pick the evolution. If you have used it, then just evolve it and see what you get.

Don't you have anything to do instead of bragging?.

If you already have enough good Vaporeon and Jolteon, then hold on to it and hope for a Gen2 nickname trick to evolve into Espeon.

Would you use sparky Trick to get a jolteon if it has max Atk ivs.

You can either try to evolve it and hope you get a vaporeon... or save it for gen II to and hope we get a way to influence the outcome of the evolution at least once for Espeon and Umbreon, note that barring some gym/stats/CP rebalance, vaporeon will still be the eeveelution with the highest CP (this is certain), and probably with the best moveset (this depends on what moves Espeon and Umbreon get).

I would evolve it and hope for another good Vape.

Eat it. No, wait... save it for Gen 2.

I caught an Eevee with around 650 cp and 95.6% iv. I was very excited until it evolved to flareon with heat wave...
So it not yet the time to be happy now.