Someone locally is selling a set of LY rods that have new ARP bolts and have been resized. I was thinking of buying them if I can get them for a good price.

Question is, if I wanted to get these rods shot peened, would the heat distort the size of the machined hole?

There isnt a ton of heat during the peening process itself, the heat generated,is from friction at that point. If they were to be baked, then they get to 600+ degrees. But, to answer where you atre headed here, NO, you do not want to shot bast them after they have been resized. It will not only ruin the honed finish of the bore ( the hone finish is critical for both sizing, and heat transfer) , it will also ruin the precision sizing of the bore which was set with the hone, Shot blasting will raise the surface, and ruin it. Some will argue you could put an old set of bearings in there, and do it that way, but not my suggestion. You can however, protect the bore with duct tape, and glass bead the rods, but ypou will need to remove the rod bolts, because too much grit will get stuck in the rod bolt holes, which you will never get cleaned unless you take the bolts out.

will taking the bolts out cause a need for resizing anyway ? that has always been my understanding.

Thanks CompWedgeEngines! That makes a lot of sense of what you wrote there.

Have them WPC'd, it won't affect the sizing, send all your parts if you have the budget...