7 meter wheels? jeebus those are huge

ok seriously now. (you mean 700c)
you can replace 27's with 700c's. just keep a couple things in mind.

a 700c wheel is 8mm smaller than a 27"
given the same tire profile (height) you'll be dropping your BB height by 4mm. so watch out for pedal strike

if you use brakes, they might not reach anymore. make sure you can lower the pads by 4mm.