ARP rod bolts - are they overstretched?

[Cevan]

I was checking the rod bearing clearance with plastigauge. I was torquing the rod bolts to 40 ft lbs and was within the range for clearance on the first two rods. On the third rod I decided to use the stretch gauge to see where 40 ft lbs put me and I'm at .011", which is over the spec for the bolts (.0100 - .0105"). Am I buying new bolts??

There was the ARP assembly lube on the fasteners as my machine shop had them when the rods were resized.

[stownsen914]

I’d call ARP and ask. They may you to check the relaxed length, torque them again, and then see if they fully return to the same relaxed length upon loosening.

It is a bit odd that they stretch above the spec.

[Tad240]

Do they ‘zero’ out to the original length (no permanent stretch or deformation) when loosened? I’d review the ARP technical information or contact their technical team to determine path forward. Hopefully you’ll get some clear answers and good news.

[proffighter]

I am not familar to the ARP stretch gauge, but if it's similar to an common gauge, you should not read the measurement while the weight of the gauge sits on the spring of it. Hold it or turn the gauge upside-down so the weight is on the fix pin. I am not saying that is the solution for your issue, just my thoughts on your pic

[Cevan]

Originally Posted by proffighter

I am not familar to the ARP stretch gauge, but if it's similar to an common gauge, you should not read the measurement while the weight of the gauge sits on the spring of it. Hold it or turn the gauge upside-down so the weight is on the fix pin. I am not saying that is the solution for your issue, just my thoughts on your pic

Excellent point. I will do the next one and take measurements at 20, 30 and 40 ft lbs.
Will also contact ARP today.

[Dpmulvan]

Rod bolts are a one shot deal, why would you plastigauge or take measurements with new bolts?

[Cevan]

Originally Posted by Dpmulvan

Rod bolts are a one shot deal, why would you plastigauge or take measurements with new bolts?

ARP bolts are not a one shot deal. They need to be torqued/stretched at least once to resize the big end.

[reclino]

Just so your aware, the ARP stretch gauge likely at its mechanical limit of accuracy when talking about .0005".
(It's able to indicate the value, but I have this same gauge, and while it's not bad, it's not a high quality Guage like a Starrett, plust it has no calibration documents to verify your example is accurate)
Each ARP bolt is a slightly different starting length. Did you zero the gauge on this particular bolt?
If you did zero the gauge on this bolt, just lower the torque to zero and verify that the bolt returns to zero on the gauge, this shows you didn't stretch the bolt and your good to go. ARP bolts should not stretch when properly installed, they are torqued in the elastic range.
David
Performance EngiNerding

[Dpmulvan]

Originally Posted by Cevan

ARP bolts are not a one shot deal. They need to be torqued/stretched at least once to resize the big end.

???? Please explain.

[Dpmulvan]

Originally Posted by reclino

Just so your aware, the ARP stretch gauge likely at its mechanical limit of accuracy when talking about .0005".
(It's able to indicate the value, but I have this same gauge, and while it's not bad, it's not a high quality Guage like a Starrett, plust it has no calibration documents to verify your example is accurate)
Each ARP bolt is a slightly different starting length. Did you zero the gauge on this particular bolt?
If you did zero the gauge on this bolt, just lower the torque to zero and verify that the bolt returns to zero on the gauge, this shows you didn't stretch the bolt and your good to go. ARP bolts should not stretch when properly installed, they are torqued in the elastic range.
David
Performance EngiNerding

^^^^ on the Chinese gauge.

[Cevan]

Originally Posted by reclino

Just so your aware, the ARP stretch gauge likely at its mechanical limit of accuracy when talking about .0005".
(It's able to indicate the value, but I have this same gauge, and while it's not bad, it's not a high quality Guage like a Starrett, plust it has no calibration documents to verify your example is accurate)
Each ARP bolt is a slightly different starting length. Did you zero the gauge on this particular bolt?
If you did zero the gauge on this bolt, just lower the torque to zero and verify that the bolt returns to zero on the gauge, this shows you didn't stretch the bolt and your good to go. ARP bolts should not stretch when properly installed, they are torqued in the elastic range.
David
Performance EngiNerding

Yes I zeroed the gauge and it returned to zero after going back to zero torque.

So are you advising to not measure bolt stretch because "ARP bolts should not stretch when properly installed", but instead torque to 40 ft lbs?

[reclino]

Sorry, worded that poorly, they will not permanently stretch when installed and torqued. It's elastic deformation so the fact that it returned to zero length confirms that bolt is still good.
Stretch is a much more accurate way of measuring tension in the bolt. Torqued is not as good. I used the ARP stretch gauge to install my rod bolts.
David

[mikedsilva]

Originally Posted by Cevan

I was checking the rod bearing clearance with plastigauge. I was torquing the rod bolts to 40 ft lbs and was within the range for clearance on the first two rods. On the third rod I decided to use the stretch gauge to see where 40 ft lbs put me and I'm at .011", which is over the spec for the bolts (.0100 - .0105"). Am I buying new bolts??

There was the ARP assembly lube on the fasteners as my machine shop had them when the rods were resized.

That's interesting.. I always find that if I torque to the recommended spec, and then measure the stretch, I am no where near the stretch recommendation. ie, it would take a lot more torque to get to the stretch.

Are these the 9mm bolts?