running hot right after starting engine

The engine right now, Has a four core alum. rad, thats made the exact same as a slant six rad. Builder made it wrong and won't take it back long story, Anyways, The car was driven home after getting alignment, about a 45 minute drive, On the highway it was around 180 degrees, with 180 themo. in it, When I hit the city part it hit 220 for a bit then got out the city and it started to fall again to 190. This trip was done with a four blade fan.
So I put on a new 6 blade clutch fan and also but on a shourd to keep it cool. Started the car up today and when about 6 minute drive if that and it hit 280 and maxed the gauge so pulled over and it boilded over. So I added water and checked to see if the themo was working, it was, and checked to see heating lines had water they did, The fan was working too.

So what do you think the problem is?