Hi can any one on here point me in the right direction or have done this,

Im looking to get a new oem subaru sti ej257 block,and was hoping as you can in america replace the very poor pistons in the block with good quality forged 2618 ones.

I carn't find anyone in uk to supply the type A and B pistons that will replace oem ones these are fitted to get the correct piston to wall clearance for correct operation, as just putting a drop in forged piston may be a little loose and to get the approx 3 thou gap required.
The reason for doing it was to have a new oem block with uprated pistons and without splitting a new block and a cheaper option to buying a rebuilt block from a company and less hassle.

 

As performance should be able to answer your question

 

the block requires stripped and honed to get the correct clearance due to not only differing tolerances but the likely hood of bore ovality even on new blocks!!