re-sizing rods

i was wondering what this is?? i heard that when you rebuild and put in new rod bolts that you should have the rods resized. what does this entail???

Resizing rods means grinding the rod/cap interface and re-boring the bearing retaining surface. The rods get a few thousandths shorter in the process.

thanks for the info. but why would do this when installing new rod bolts? or do you not really have to??

Yes, you have to. Rods will take a size when the caps are on and torqued, new rod bolts will change the relationship between the rod and cap and your rod big ends end up egg shaped. Consider it essential when replacing the rod bolts.