OldOldsLover

Hi,
On my 70 455 took out the piston/rod and have reinstalled them.
The torque spec is 42 ft. Lbs.
When i took them off it seemed more like 60 ft lbs but this is just my guess by feel.
I see know that the torque procedure is different now a days...
https://youtu.be/im1YgvBvV_8

https://www.cpgnation.com/how-to-measure-bolt-stretch-for-proper-torque/

can't copy link properly

So on used rods with factory nuts and bolts my question are...
1. is 42 ft lbs the correct torque?
2. Can they be torqued over 42 without issues and if so what is that number?
3. Does anyone use this torque angle procedure?
4. The nuts on one side are smooth and flat, the other has a pattern of shapes, does the smooth side go down? See pic below

Thanks in advance
I tried searching but didn't find answers
OldOldsLover

oddball

Installation torque is not the same as disassembly torque. Ever. Very different things are happening with the fastener so you can't directly compare.

Bolt stretch is the best method to install a fastener. That tells you precisely how much load the fastener is experiencing so you can get it exactly right. Installation torque has a ton of variables- muck on the threads, deformed threads, why type of lubricant, how you're applying the torque (smooth? fast? slamming it?), etc.

I've only heard of using torque angle in torque-to-yield bolts. I only skipped through that video but couldn't really tell what he was talking about. Regardless, follow what your bolt manufacturer tells you to do. e.g. ARP will provide bolt stretch (if you're using a stretch gauge) and torque (if using their moly lube) specs.

When it comes right down to it this is a nice tweak to the assembly procedure. It's not essential to measure bolt stretch.

1) Stock bolts in your rods? Check your assembly manual and do what it says.
2) No. Go too far and the bolt will fatigue and fail. Especially OEM rod bolts. The Olds bolts are pretty good, but they'll still fail.
3) If the bolt manufacturer says to, sure.
4) pattern of shapes???

joe_padavano

A bolted joint needs to have correct preload (tension) in each bolt to properly carry loads without gapping. That's how you design a high-strength bolted joint. The most accurate way to gauge proper preload is to sense it directly. In critical bolted joints in aerospace we actually use instrumented bolts - they have a strain gauge inside them and we read this out while tightening. Second best is a load sensing washer, which has an indicator when the proper compression load is reached. Bolt stretch is nearly as accurate, assuming the dimensions of the bolt are tightly controlled, but you need to calibrate the stretch per pounds of tension for that particular bolt configuration to use this technique correctly. The thing you are clamping is compressing while the bolt is stretching, and you don't know how much that lowers clamping force.

Torque measured with a torque wrench is about the least accurate way possible to set proper bolt clamping force. Friction between the nut and the bolt threads, friction between the nut and washer or bolt head and mating surface can vary wildly, so you have no idea how much of the torque is turning the fastener and how much is just overcoming friction. Tension in the bolt can vary by a factor of two or more for a given torque depending on friction, lubrication, etc. Now throw in calibration accuracy of your torque wrench, accuracy in how you actually use the torque wrench, etc, and you can see how tension in the bolt can vary. Older engines like this have such insanely conservative margins on stress and strength that this typically isn't an issue. New engines that have every last ounce shaved out of them use torque-to-yield fasteners in critical applications.

oddball

That looks like the pockets the machine into some nuts to hold oil/grease/lube during assembly. Reduces friction between that face and the thing being clamped so you get a more repeatable torque reading.
Again, not strictly necessary, but you can put a thin layer of lubricant on that face and install the pocketed face down.
E.g., *some* ARP nuts have that kind of setup, some don't. Some ARP washers are beveled to give excess lube a place to go - some aren't. Just tweaks and preferences.