The walls are fine, on a closed deck motor. But it's the FRM lining and the softer material used on the pistons that cause the pistons to melt and/or the block to seize when you put boost onto a H22 motor. When you put forged pistons into the closed deck H22 motor, you need to either resleeve the block or reline the cylinders with some iron sleeves (generally cheaper and easier) or the forged pistons will seize up with the FRM walls.

However, H22 closed-deck motors can take a lot of NOS if you put in on that