Two minimum bro, and at your weight I'd start with three. For pain I've used as much as 6 at once, but that was after several days of consecutive use when I had already built a higher tolerance. The thing with vicodins (and all painkillers for that matter) is that one builds a tolerance to them almost instantaneously, so that by day 2 or 3 of consecutive use, you won't feel any pain releif or euphoria from the dose that seemed ideal just several days before. That's why it's best advised to use it for no more than 2-3 days in a row, and it would be ideal to follow that with a 4-7 day break, so that you don't get dependent upon them and when you do use them again, you can use a similar dosage without having to use more to obtain similar effects as the initial one. With all that said, the first time I was prescribed vic's for pain about 2 years ago following surgery, I took 2 and felt great, but at that time I was only 190 lbs. And the following day after taking two, the effects were blunted already!
Recently, I disclocated my thumb and was prescribed some more once again and after taking 2, felt hardly anything. Bumped it up to 3 and all was well. So bodyweight is indeed a factor in dosing, since I am now around 215 lbs.