Hi Dave, well, ideally I would replace all of them with new ones, as I prefer not to reuse bolts in such critical applications. Second-best would be to replace all of them with better-looking used ones, as most of mine have some amount of damage to the shanks. At the very least, there is one bolt that looks particularly bad, so one would be the minimum I would need. You also never know when someone may have overtorqued them at some point.
So I guess it's kind of up to you and how many you are willing to part with and what condition they are in. Are they all used or are any of them new/NOS?
Most of mine got scraped and gouged up quite a bit when they were installed into the rods during prior rebuilds. Maybe it's just fine to file down the damage and use them, but it makes me nervous. Also, the heads on several got pretty mashed up, and the only thing I can figure is that someone was beating the pistons and rods out the bottom of the engine (not me). Most of the piston skirts are broken off to varying degrees, so that may be further evidence of this. The one that is the worst has shank and thread damage, too.
and have an overall length of 2 9/16.
