James Franco & Zachary Quinto -- Locking Lips And Checking Packages

James Franco is teasing the Sundance premiere of his new film by teasing co-stars Zachary Quinto and Charlie Carver in a steamy hot shirtless pic of them sucking face and going at it.

If you somehow missed it, James will assume the position of Michael Glatze -- a former gay magazine editor turned anti-gay activist in the upcoming flick, "I Am Michael."

He just posted these pics on Instagram to give us all a taste of what's coming ... but if this is just the tip of this NSFW 3-way, we can assume things will get even steamier.

One thing's certain ... if you see this at the festival make sure you bring a tissue.