i have an sti 7 and have already put a piston in the right hand bank,on firing up the engine for the first time we now have a tap from the other side,a mate of mine has stripped the engine down today and the front piston has picked up,my question is what does the "A" and"B" on the pistons denote,is it size or which bank it goes in,would it be possible to put a "A" piston off one side into the other and vice versa,who would be the best person to speak to regarding this?

cheers
jon

 

A & B are the sizes. A being bigger than B.
the block is stamped with the bore sizes in A or B on the top center join

cheers
Steve