Anyone have a rod bolt they could loan me or know their measurements?

brianp454 said:

I've seen lots of speculation about the rod bolts here, but never any data. I tried in vain on one of those threads to get someone to properly document a failure, provide samples for a blown engine, take measurements on the non-broken rods of the blown engine, etc. I'd like to see one or more of the of the White\Herc\Cont. pulled on a tensile test machine to see if there is an issue with the bolts themselves.

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mark salanco said:

Guess everybody is to busy to take the time.

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I must have missed something. Do I need to send a rod bolt to one of you? Please send me a PM if there is something I can help with. I would love to think my motor has something stronger than "stock" in it.

Tensile test

Wow! At hit! I recall a thread where a guy showed a pic of the hole in his block, but he never provided more info. I'll have to find the thread and re-read my own thoughts. I'm curious about the torque required to remove the nuts, friction\quality of the threads, stretch test, or if possible a full-on tensile test to failure. I'm AssUming that if the bolt comes out it is due to stretch or that it wasn't preloaded properly. If you poke around ARP pushes for using their own lube to get more consistent preloading when tightening the fasteners. I think I put a link to it in the other thread.

Let me poke around and see if I can get access to a tensile test machine and if I can jig something relatively easy. I have a few days before I have to take a biz trip to Japan for work, so I'll be tapped out for a while. Will get to it as I'm able.

gimpyrobb said:

I must have missed something. Do I need to send a rod bolt to one of you? Please send me a PM if there is something I can help with. I would love to think my motor has something stronger than "stock" in it.

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mark salanco said:

Guess everybody is to busy to take the time.

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Busy to take the time for what? Personally I don't see the gain in paying $324 or more for a set of rod bolts that may or may not be the problem. (BTW to do this properly we probably should have a rod removed completely, install the bolt to whatever spec, then have the end checked. I bet it will have enough distortion in it requiring a resize of the rods.

I agree, i think having the rods resized during a rebuild should be standard procedure. If a rod bearing has been spun, that rod will be junk and not serviceable !
Same with main bearings.

Diesels have new inserts installed all the time during an in-frame overhaul and aren't resized. Why would the multi be any different? If the new bolts are tightened to the same torque, what has changed?

JasonS said:

Diesels have new inserts installed all the time during an in-frame overhaul and aren't resized. Why would the multi be any different? If the new bolts are tightened to the same torque, what has changed?

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The rod caps can distort if the bolts are replaced and clamping load is increased.

AFAIK, the 12pt bolts have the same torque spec. We really aren't talking about increased clamp load as being a requirement. Instead, what we need is better fatigue resistance.

All bolts stretch when tightened. They never completely return to the factory new length when removed. In many applications that small change has no impact on service life, but in the LDT/LDS it seems to be a factor. Or it could be the torque applied during rebuild... we don't know.

When we rebuild our engines, we always check for proper rod end dimensions and rod length and rod twist. Especially on the Detroits. On the new Cummins engines we just use factory rebuilt rods. We don't even bother checking them.

Hey guys. I have a contact locally to run samples on a tensile test machine to see if these connecting rod bolts are really an issue. If any of you have extra parts lying around please PM me for my address and send the parts you have to be tested. Please also include any info you have, especially a digital file of the engine data plate or other info such as manufactuer, year, if it was rebuilt, etc. Thanks in advance!