Hi guys,
Decided to replace my rod bolts , eagle rods , 8740 arp. , unknown history.
Decided to try the stretch method as it makes sense to me. Previously only used torque spec.
I realize my torque wrench is old so felt the stretch method could discount poor wrench calibration.
I am using the method of stretching the bolts with rod in a rod vice and recording torque required to do so .
I am following the arp guide lines and using their supplied lube.
I have read through all of the threads here I could find so I could best understand the process and methods.
I have done one rod and was able to achieve the recommended stretch.

My concern .
In order to achieve the recommended stretch I am 37 ftlbs over the speced 63 ftlbs.
I am going to try a different torque wrench tomorrow to see if the value differs.

Is what I’m finding typical for an amateur with average tools?

Thanks for looking
G

Wow!!! So you are at 100 foot pounds.

I'm no pro BUT I've had ARP 2000 rod bolts that took forever to hit their torque spec - which is totally counter to what you're seeing. Talking to seasoned engine builders its a fairly common thing. If that's what it takes, that's what it takes !!!

LOL cmon man, who wants to see that response!!!!!!!!!
Omg that made me laugh!

Yeah but maybe my t wrench is off by 20llbs.?

That’s why I’m asking , Don’t know what I should be expecting
G

[quote=Stanton]I'm no pro BUT I've had ARP 2000 rod bolts that took forever to hit their torque spec - which is totally counter to what you're seeing.

“Talking to seasoned engine builders its a fairly common thing. If that's what it takes, that's what it takes !!! “

I have read this as well.

Here is one data point. Hopefully some engine builder with lots of data can give you a summary of expected results.
It did take some getting used to using the fixture with the dial indicator on it to get good, repeatable results.
FWIW. These ARP 2000 bolts took 75 ft-lbs instead of the 70 ft-lbs expected to get the stretch.

The torque needed to reach the desire length can and will vary with ARP bolts, especially if they are custom made ARP 2000 for one of the high end rod makers like Molnar
I've seen those bolts over stretch at 53 Ft. Lbs. on one bolt and seen others in the same batch of rods take 83 Ft. lbs. to get in the middle of from .0057 to .0062 bolt stretch
Which ARP bolts are you going to use?
Do one at a time and record the torque needed to get the stretch where you want it and keep it for later on if your planning on looking at the rod bearings so you can retorque them back to exactly what they needed to stretch properly.
Do not use the torque plus so many more degrees of rotation to tighten them

So are you going to have the big end checked after the new rod bolts & different way of tightening the bolts thus changing the amount of clamping force ?

Thanks for responding mr cab . They are 8740 arp

I build a few engines, I am not a high end engine builder. I do use a rod stretch gauge when the rod has the proper bolts. My experience is that it usually takes 5 to 10 lbs more torque to stretch the bolt to specs given. I have never seen something like you describe. I build about 7 to 10 engines a year.

Hmm thanks
G

My experience with using stretch is the torque readings vary greatly. The last time I used torque angle specs provided by Tom Molnar. The stretch numbers were very close. The torque numbers were recorded using a Snap-on electronic wrench. The numbers were much closer together. Sneaking up on stretch creates a lot of friction skewing torque readings. As stated if you don't have a good method to measure each bolt at the start and finish and keep exact records the entire process is useless.
Doug

Ok thanks all. I am going to trash these bolts get two more and just torque them to spec. With a known accurate wrench
G

Tried the gauge on another set of the older bolts. Definitely something wrong, similar results. I ordered a new gauge .
Spoke to Eagle. The gentleman I spoke with felt sure that the rod was not damaged .
Thanks for the knowledge .
I learn something every time I work on this thing.

I still use the torque method(because I dont have a stretch gauge).. I still have my torque wrench calibrated
and its still good to go

My results are similar to yours. ARP makes real hard bolts. And trying to get them to stretch takes way more torque than I want to put on a little rod. Why does everything have to be so complicated? Sometimes I just torque them to the recommended torque realizing that I surely didn't get them to the stretch that it calls for. Bear in mind that everything is going to be fine and it's not going to come apart because you didn't get the proper stretch.

Modern OEM engines solved a lot of the bolt issues by going to torque to yield type bolts. I try to think about bolts like rubber bands, the tighter you tighten them the more they stretch the more the more clamping load they develop. And just like a rubber band you stretch them too much they break. The other concern is the components they hold together can only take so much clamping force. And equal force on parts with multiple bolts is a big issue as well. Torque to yield bolts are designed to stretch past their yield point, which means they will not return to their original length when released, In doing so the load is more constant and you can use a smaller bolt for same clamping loads. I hope everybody knows that a click type torque wrench, should always be rotated to zero when in storage, if you leave a load on the mechanism it will cause problems. I prefer a dial type torque wrench. I use a click type when I can't see a dial, like putting a head on in the car. On the engine stand I always use a dial type, and they are the most accurate.

https://wbtools.com.au/blog/how-to-choose-the-right-torque-wrench

Torque on rod bolts need to be consistent. Do every bolt the same. First torque each rod in a soft face jaws vise. Torque each bolt at least 3 times to torque specs, using the proper lube. Make sure to put lube on the threads but also on the mating faces of the bolt face and the rod surface it mates to. Carefully doing each bolt the same. Then if using stretch method torque each bolt to stretch spec. and record torque reading. Install at same torque and check stretch. Myself I'm an old timer and only use the torque. If you do also, just make sure of using lube on all mating surfaces and torque several times before install. And Good Luck

I have a middle of the road click type that is about 20 years old- where would I get it calibrated or is there a calibration tool I can buy??

Look at the brand name and call that company.. a lot of places have equipment to cal them... I use to
get it done at work then from Snap On.. check the tool trucks for there service