Well I recently did a trade with a friend and come to find out he dropped off with me a low mileage b21 block, so I do what any other inquisitive individual would do and decide to tear it down and see what makes this so different, the biggest thing I notice right off the back are the cylinder walls, I have torn down, rebuilt, or at least seen the internals of every honda engine, and this version of the FRM sleeves are the most interesting and unique of the bunch. I can honestly say that this is the only block I have seen with the sleeves like this. The honest and only good thing I can see of this block is that it will have fast ring seal and break in period. In all honesty if I was aiming to build an engine that would only last 50k at the most under a life heavy abuse and pushed to its maximum performance this would be the block bar none and I wouldn't touch the sleeves. Also I have some jdm B20A piston and rod combos, I'm taking one of them along with the b21's to get a weight comparo to see if the necessity for the lowered rev-limit on the b21 is really that necessary, or did Honda just freak out. Also I noticed that the block is stamped as a PK1, and the rods are stamped PK2, only the pistons and the IM are stamped PK3, the head may have PK3 as well but I didn't notice nor did I look into it. Also I will be dynoing this setup to see what I can pull out of it, and then I'll be doing the same port and wolish work to the b21 head so if anyone would beinterested keep your eyes on Ebay, becuase I know you bastards would just dance around the issue of actually buying it, lmao JK.