[Shiny]

If you tightened to the correct bolt stretch and it distorted the rod, find out why. Sounds like the rod was machined assuming less stretch (bolt tension) or to a torque spec. IMO the mismatch leaves you open for grief. Call the rod manufacturer...

[Dragncar]

I ran my 8740s to 63lbs and no issues.

[SD421]

Just found my instructions from RPM.
Torque them to 60ft lbs

[HWYSTR455]

It's easy to get in trouble with a click-style torque wrench. Method used to 'pull' can vary drastically from user to user. And I've had people argue with me regarding how it's properly done.

Once, watching a guy do a BBC build, he would pull kind of fast and gave up after the first click. When I mentioned it was not 'the best way', I got the "I've always done it that way and never had a problem' comment.

I asked if I could check it, and I came slowly up to the about where the click would be and it moved without clicking. I slowly added more pull and it clicked. But it was at least another 1/8 of a turn.

Then there's the argument of wrench calibration.

I've heard people swear beam type wrenches are more accurate, and I suspect some of it may be due to the fact that your are basically forced to come up on the spec slow. Going the last 5lbs or so even slower.

Totally agree on the lube too, have to use what is specified my the bolt manufacturer.

Have to closely inspect the hardware too, ensure threads are clean, and run the nut or bolt down by hand once or twice, feel the threads so to say. I've seen ARP bolts come out of a box of main studs and one nut had zero threads.

If nothing else, it removes all doubt if something later goes wrong, making sure of every detail along the way.


.

[Lee]

I rotate the motor so that my stretch gauge is pretty much vertical. I've had some funny readings when the gauge was at more of an angle.

I've used LONG box-end wrenches, and tightened bolts without removing the stretch gauge - you need a LONG wrench, and this is a slow & tedious process.

Now measure the bolt, carefully remove & hang the gauge where it will not be disturbed, then torque the bolt/nut. I remeasure. If insufficient stretch, then I back off and retorque with a slightly higher torque. Repeat until I find the torque that puts me in range. I check every bolt this way.

Recently, I was working on a motor that was poorly built by a shop (lots of issues!). When following the above stretch/torque process, I came across two bolts that stretched excessively at the same torque that put the other bolts on the low-end of the stretch! Re-tested both several times to make certain. Bought two new ARP bolts, and they fell right in-line with the other 14 bolts. No telling what had previously been done to those two bolts, but I did not trust them.

[sdbob]

Not rod bolts but hardened find thread. One nut I could not get started. I was at Kennametal took it to work put it under comparison microscope , IT HAD A DOUBLE HELIX!! I have no idea what that was for never even heard of one.

[SRGN]

Aftermarket rods, go with manufacturer recommendation. Rebuilt stock rods, go with the method used when the rods were sized. Stock rods/bolts, I torque but check with a stretch gauge to confirm the bolt hasn't been pushed past yield. I personally prefer stretch method on any ARP rod bolts, I've also started using the ARP 2000 series bolts for everything, they have been more consistent in the applications I've used them on. As far as torque wrenches, hard to beat a quality digital one these days. When I do rod bolts, I will torque then loosen the bolts 2-3X before final torque or stretch measurement.

[HWYSTR455]

Yup, 2000 series are the way to go, and if the rod vendor has an upgrade option, even better.


.

[Shiny]

Maybe the source of the "spec" is part of the churn? I expect the rods and the application to dictate the fastener specs, not the bolts.

Originally Posted by charlie66

I always snug the bolt until I feel it seat the rod and cap tight then in one motion pull it to the torque value I'm looking for.

Has anyone ever stretched an ARP 8740 bolt to spec and have to go to or more then 78ft lbs.?

Is this a spec from ARP or from the rod manufacturer?

This:

Originally Posted by SRGN

Aftermarket rods, go with manufacturer recommendation. Rebuilt stock rods, go with the method used when the rods were sized. .....

[Dragncar]

If you go to 2000 bolts with a rod that was made for 8740s you are going to need to resize it.

[HWYSTR455]

Even new rods, regardless of bolts, you need to 'size' them for the build at hand.

If they come with 2000 bolts, you don't have to have the bolts fit.

At least that's the logic I use.

If a rod manufacturer provides a rod with ARP bolts, the manufacturer's spec will work.

Otherwise, use ARP's spec, of the machine shop that fit them and resized the rods.

Another reason buying a rotating assembly makes sense.

Again, the logic I use...

.