question about con rod fasteners...

i'm pretty sure i've read that the clamping force of studs is superior to bolts, otherwise... why use 'em? another bump

consider what the bolt is threading into. cast iron? stud is a major improvement. threading into 4340? a bolt will do just fine. and you're not relying on the fastener for alignment of the cap. the rod can also be profiled for more clearance without a notch at the base of the beam.

I'm not a fastener engineer, but I'll take my best guess at it.

First of all you need to think about the total length of a rod fastener vs. a main cap fastener. If you use a bolt on the main cap, a large portion of your torque is actually twisting the bolt itself, not threading it in further. So the force is transfered through the large shaft of the bolt, before it can get to threads. Since the main bolts are very long, this creates a twisting problem (think torsion bar). If you put a stud in it, the force is immidiately put on the nut to tighten the fastener. It doesn't have to go down the shaft of the stud to get to apply the energy to tighten it.

Rod bolts are obviously much shorter, and don't have to deal with this problem. Also, if you think about putting studs in a rod, the top portion of the stud is actually fairly thin. That thin section is the only thing preventing that stud from pulling through the rod. Also, this creates a very high stress concentration at that loading point. Where as if you put a bolt in it, the threads help distribute the load through the rod more evenly.

Lastly as mentioned, the profile of the rod can be trimmed down (lighter, more clearance, etc...) if you use a bolt.

Like I said, I'm not a fastener engineer so someone may tell me I'm wrong?

But that's how I see it...

interesting. i've also often wondered where material is removed from the newer style rods for balancing as there is no pad at either end like an oem rod. as you can probably tell i'm still in the dark ages using the orig. LY rods and std orig cast pistons in what is probably a horribly out of round barrel shaped bore. but i digress, so to balance an h beam material is removed from the area that the bolt head on an ly rod would be? btw i'm still not sure how a cap screw is stronger than a nut on a rod bolt but maybe i'm just

material is removed from the ends, same as i beams. i've only seen very small amounts removed. my guess is that manufacturing methods are much more accurate these days? even overseas? stand by for imbroglio!

On the subject of aftermarket h-beam rods, does anyone NOT re-size their rods with bolt replacements when they have dowels to locate the caps?

That doesn't sound right to me, most high dollar bolts with partial thread lenght are necked down to the small thread root diameter anyway, to even out stresses anyway, if I understood your comment correctly.

Doesn't that area need to be "broached" regardless if its a bolt or a stud/nut?, and therefore not a factor regarding the better solution?

No the cap still needs to be broached but the rod is not..

Yes, you absolutely correct, guess I was only looking at one "side", pun intended