rod bolt torque compared to stretch

[modok]

Sounds right to me, carry on!

[fast_crew]

Clean ARP lube off of bolts and rod threads, relube with CMD #3, torque to about 20lbs first pull, then creep up on final torque required to achieve stretch.

[donc]

Might want to consider contacting Tom Molnar, his rod bolts are made by ARP,but to his specs, they stretch to the recommened torque. If it says 30 ft.lbs. then an additional 40degrees will yield say .0065. they do the first time and repeat.everytime. His bolts are designed correctly. He also supplies extreme lube #3 with his bolts.

[grandville455]

Bringing up a older thread as I am installing some of Ed’s rods , he said his stretch normally comes in around 86-92 ft lbs, and I’m seeing about 86-88 ft lbs with .0064 stretch . I have talked to others and they see closer to 75#, isn’t the stretch value the important one and not the actual number on the wrench ? They may be using more lube or something to only achieve that stretch at a lower torque setting? I lube the threads and under the head and then thread until it touches,install gauge and zero it and then back out and relube threads and under the head and then tighten to where it just touches again and then in one smooth pull I torque to that range and recheck with my zeroed gauge and it’s right there! The wrench is also calibrated often that I’m using.

[steve cowan]

Bringing up a older thread as I am installing some of Ed’s rods , he said his stretch normally comes in around 86-92 ft lbs, and I’m seeing about 86-88 ft lbs with .0064 stretch . I have talked to others and they see closer to 75#, isn’t the stretch value the important one and not the actual number on the wrench ? They may be using more lube or something to only achieve that stretch at a lower torque setting? I lube the threads and under the head and then thread until it touches,install gauge and zero it and then back out and relube threads and under the head and then tighten to where it just touches again and then in one smooth pull I torque to that range and recheck with my zeroed gauge and it’s right there! The wrench is also calibrated often that I’m using.

I think alot of people don't pull the rod bolt in one cycle so this leads to a higher torque wrench value.my opinion what you are doing is correct as I do the same.
Madbill on this forum recommendation for the rod bolt pull in one motion deal and I have used it extensively.
As long as the bolts zero back I don't see a issue and alot of guys will work out stretch/ torque on one rod and then use the tension wrench value for the other rods to save some time.

[modok]

If stretch can be measured accurately than that is the best way, but there are many situations where measuring stretch is difficult or not possible.
In THAT kind of situation then we need to look at finding ways of making torque repeatable, and there are ways, but if it's not needed then..... it's not needed.

[tuffxf]

The cmd3 lube is excellent as is the old arp lube!
The new arp ultra lube is no where near the same as the old stuff, it requires a lot more torque to achieve the same stretch and is not as consistent as the old stuff!
There is info on this out there, caused a lot of issues when they changed.
Most new scat or eagle rods when tightened correctly will need to be touched up to get them round.
Cheers

[GARY C]

It always seemed to me that if you have to over tq a bolt to stretch it to a specific length it can't be good for the bolt.

[steve cowan]

The cmd3 lube is excellent as is the old arp lube!
The new arp ultra lube is no where near the same as the old stuff, it requires a lot more torque to achieve the same stretch and is not as consistent as the old stuff!
There is info on this out there, caused a lot of issues when they changed.
Most new scat or eagle rods when tightened correctly will need to be touched up to get them round.
Cheers

I once used the high pressure lube from my jesel rockers.
So much smoother.

[Tom68]

It always seemed to me that if you have to over tq a bolt to stretch it to a specific length it can't be good for the bolt.

But the actual stretch is so much more important than the torque applied.

[Rick!]

Scat +1 (310) 370-5501

Rod bolts are not "torque to yield".
When you call up Scat, you'll want to ask them how many torque cycles are allowable before replacing the bolts.
Some will tell you 4 torque cycles, some will allow 6 torque cycles. I would say you need a couple of new bolts before assembling the engine.
They only good thing that happened while going through the exercise is that the joint is now conditioned, which means the bolt threads and rod threads and the bolt face of the rod have rubbed on each other enough to remove surface imperfections. The thing is, though, is that after repeated conditioning, one set of threads will start to deform and torque value to hit a stretch number will become inconsistent again.
You may also want to do some bolt stress calcs for both tensile stress and compressive stress under the head. 8740 bolts are advertised in some places to have a yield of 190ksi. At 95lbf-ft of torque, you're pretty much there. As the one gentleman stated, if you came back after 4 hours (in my experience) and rechecked stretch, you'd find a significant relaxation, especially after embedding the bolt head into the rod.
Follow the torque guidelines, which are pretty much the same as Eagle, and you should be good.

[HQM383]

It always seemed to me that if you have to over tq a bolt to stretch it to a specific length it can't be good for the bolt.

But the actual stretch is so much more important than the torque applied.

I have to agree with you there Tom. It’s the tension the bolt is under due to it’s stretched condition that provides the necessary clamping force, not the twisting force applied to tighten the bolt. Just look at LS critical bolts tightening specs. Low ft/lb to seat joint, then angle rotation spec to set stretch. A 7/16 - 20 tpi bolt will rotate 33 degrees to stretch .0046”. Wrong lubricant can under or over rotate before the wrench click leading to under or over stretching of the bolt - under or over clamping of the joint.

[grandville455]

I’ll check a couple of them and see if stretch is the same next time I work on it, probably Monday, I hade sure when I zeroed the gauge and wiggled it some that it repeated to zero , then I pulled it in one even pull til it clicked , set gauge on and wiggled it and it was right in spec for stretch

[steve cowan]

I’ll check a couple of them and see if stretch is the same next time I work on it, probably Monday, I hade sure when I zeroed the gauge and wiggled it some that it repeated to zero , then I pulled it in one even pull til it clicked , set gauge on and wiggled it and it was right in spec for stretch

Most times once I have checked bearing clearance with rod only,and know what to set torque wrench/stretch lets say 75 ft/ lbs and 0.006" stretch I just use torque wrench when pistons/ rods go in the engine.
I also like to get feeler gauge between both sides of rod before torquing up rod,keeps everything snug

[steve cowan]

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