Some boars can live in 2x4 others..not so much. My cage is 3x4 with a 2x3 upper level and I swear if it was any smaller I would have had some serious bloodshed.
Did you follow these rules:
http://cavyspirit.com/sociallife.htm
Guinea Lynx :: Companionship
It is not common for them to fight so intensely that anyone gets injured beyond a "butt scab", however for young boars a 2x4 is a bit small. Males will push and push at their territory, and if the passive pig has no way to get away, he will get it until the aggressive pig gives up, or kills him. It depends on how aggressive the aggressive pig is.
The way I chose to deal with an overly aggressive baby boar, was to allow for plenty of space, and about 6 various hiding spots in the 2 level cage. I made sure that all hideys that have multiple exits (so that no one gets trapped inside and attacked) I made sure that there was unlimited hay, pellets and water in two locations as well. I also never separated them at any time. Floor time was together, lap time was also together. Everyone told me that separating them and putting them back together makes them have to re-establish their place each time.
I credit the success of my pairing of these two boars to the fact that the habitat was so large and had so much to do that they would lose interest in the fight after the loser ran upstairs to cool off when the aggressive pig was in a bad mood. Essentially, I think they were fighting over the "level" instead of the cage. In addition, the loser could always get away from an attack. I have two identical hideys and bent grids for tunnels etc. Then everyday I moved it all around to keep their minds occupied. I used fleece cage blankets to lay over sections so that had places to play. Stuff like that. I used everything I could to keep them occupied. They still bickered and had occasional fights, but no serious bloodshed
One important element was also that they normally got along. Shared the same piece of lettuce, hang out in the hay bin etc.. They did rumblestrut ALL the time during adolescence with the occasional head butt. However, they only got into "fisticuffs" on a few occasions, and I did find several butt scabs over the weeks and one time had an ear get bit or cut. No serious injuries so I left them together.
Any fights happened so fast that I didn't even have time to separate. I attribute that to having plenty of room. The loser would go upstairs and wait until "the old man" settled down. Of course, the aggressive pig was the baby, only 5 weeks old when introduced!
My passive pig LOVES to be with the aggressive pig and that is when things would get tough. After a few months they stopped almost all aggression and now they only rumblstrut. They even sleep near each other a lot now.
Have you tried buddy bath?
Are there females in the room?
In my case, I chose for larger habitat. Some folks do find that the divider thing works others say it didn't.