OK, now where getting somewhere. BUT, what comes to my mind, is that you told me your teacher has mic'ed your block and said it does not need to be bored. He also suggested to use Moly rings on a re ring job, which is a no no, and I have back up now to say the same thing. So here is where I lose all credibility with your teacher. If he measured your block for you, why didn't he tell you this this block has already been bored .030 over??? Did he really KNOW what he was measuring and what spec was he using and where did he get the spec from?
On another note, if the motor has been rebuilt before, now you have to wonder how much use did it really get, and there is a good likely hood you don't need a bore. How does the crosshatching look in the cylinders? Does it go all the way thru the cyliders? Is there any kind of ridge whatsoever at the top of the cylinder where the top ring lands? If crosshatching is present and well definded, no ridge to speak of, then I'd use a ball hone and freshen up the crosshatching, REPLACE THE ONE PISTON YOU BROKE, and I'd put it back together. For real, its OK to replace one piston. It might even be a hair different than the rest, but just so long as it its got the same dish, or flat top liike the rest of them, and ring groove sizes and run it. No need in buying a full set of pistons when you only need one. If you needed, 3 or 4 pistons, then yes, I'd probably go with a whole set cuz buy the time you buy them at singles pricing, it woudln't be far off from a full set anyway. You're not the frist one to break a piston. Its common for a builder to have one fall out of the block off the engine stand and break a skirt off. Some guys even run the piston with part of the skirt broke off. I won't do it, but point is, it's not big deal to replace 1 piston as needed.
