160 CFM enough

I am in the process of making my own sealed grow room and was planning on exhausting through my air-cooled hood. the problem is i have 2 80 CFM fans from a previous grow, my thought is if i had one fan just out side the fan pulling air from the hood and the grow room and then use the other fan to help pull air and run that fan into a carbon filter would that work?
the room is 2.5'x2.5'x6.5'

Yes.

First, those duct fans suck for moving air. They are for boosting already moving air, back pressure will rapidly take that 80 cfm to 0 especially through a thick carbon filter.

You need to buy one of THESE (dont second guess, cheapest price on net)

The 4 or 6inch blower will be really effective at exhausting air AND cooling a HID light if you eventually go that way (sealed hood air cooled lights are awesome). You will be amazed at your temps but most of all, if you were using crappy fans with a carbon filter its massively boosted effectiveness will make you think you bought a new one.

so your saying just use that one to exhaust the grow room or could i use the other fans to maybe boost the cfm so that there is more CFM exhausting.

Use it, as for your other fans, circulation, boosting or intake, but you need an active air exhaust, try a blower, you will not be dissapointed.