Originally posted by inspyral
If your definition of "fully built" includes new sleeves, I would go with the B18C1, hands down. You can take a B18C1, sleeve it to 84mm, put an LS crank and LS rods in it, and you'll have the displacement of a B20, plus VTEC with OEM block girdle, VTEC oiling components, and OEM reliability. A B18C1 resleeved to 84mm would also be a lot stronger than stock B20 sleeves. If you're trying to boost on stock B20 sleeves, you can't run all that much boost before structural integrity becomes an issue. The B20 sleeves are one-piece and at a glance would seem more sturdy than the induvidual B18 sleeves, but the areas between the cylinders on the B20 sleeves are the weak points. This would lead one to conclude that, in order to run anything beyond moderate boost on a B20 block, it is necessary to have it resleeved. If you're going to be getting new sleeves anyway, why not just sleeve a B18C1 to 84mm and have all the VTEC components as they came from the factory, rather than trying to add them to a B20 block.