...But isn't the recommended torque selected to give you (approximately) the proper stretch? Stretch is all about the clamping force which keeps your rod cap on as the piston reverses at TDC...
...
Aha!!! ...and that right there is where I'm stuck today, at least mentally that is. You expect a bolt to stretch by a given amount provided that you apply a certain amount of force that causes the bolt to get elongated. That force being defined and measured as torque.
I haven't had a chance yet to try other rod/bolt combos, which I will tonight. In the meantime though I did get a pretty quick response (a couple actually) from Eagle regarding my follow up questions, basically the matters we have been discussion in this thread here.
My 1st email to Eagle:
Alright sir, so here is the situation I have and I'm wondering what I should do at this point in time.
What is a safe torque to build up to as I attempt to reach the bolt stretch?
These bolts are meant to go 0.0064-8 at the recommended 75 ft-lbs of torque with the ARP lube. Good stuff, but I only see 0.0048 streatch and it only climbs to 0.0051 at 85 ft-lbs. So things are barely moving!
Here is what I'm actually seeing starting at the 65 ft-lbs mark:
TORQUE INNER-BOLT OUTER-BOLT
65 4.3 4.3
70 4.5 4.6
75 4.8 4.8
80 4.9 5.0
85 5.1 5.1
So I am still quite some ways away from the recommended 6.4-8 stretch, but having already gone up to 85 ft-lbs I am extremely uncomfortable going any higher.
The tightening torque has been checked with two torque wrenches: one digital, the 2nd one a click-type, they both match.
The bolts are using a good measure of the ARP lube, not overkill, just well coated, both the bolt threads as well as the under-head.
I have not tried any other bolt/connecting rod sets yet, only this 1st one.
Thanks,
-Dariusz
Eagle's 1st response:
Hey Dariusz
The proper way to do stretch is closed in wrench and install gauge and pull to the stretch your looking for. Do look at torque. Now if you want to torque it, dont look at stretch. We use the torque method here. So pick one and go with it, Both work.
They will never match.
My 2nd email to Eage:
Ah, so let me clarify.
I actually have the rod installed in a rod vise. I get both bolts torqued to 25 ft-lbs before I start the final tightening sequence up to the 75 ft-lbs recommended value.
Prior to doing this I check the free bolt length, and I check it afterwards as well. So far there is not stretch that I am able to detect. So this should be good news and implies the bolt returns (springs) back quite fine.
Based on what you wrote below though it does not sound like you are providing a max torque to get that recommended 0.0064-8 stretch though...man, I can go up further, but is there a realistic point of "no-return"? Meaning, I've stretched the bolt too far using just the TORQUE approach?
Thanks,
-Dariusz
Eagle's 2nd response:
Your correct, we don't offer a max torque, Torque will be lower than stretch always. So just pick one and go with it. Again I use torque on my motors and never had a failure do to the bolt torque. Both processes work. Just don't look at the torque is your doing stretch.
Man...if I felt frustration initially while attempting to get me a good measure of bolt stretch, that literally pales in comparison to what I'm feeling right now.
Keep in mind I'm an overall newbie in the bigger scheme of things, but I am clearly reading, watching, hearing people out there talk about rod bolt stretch and the bolts having a defined yield value. And here I have a manufacturer that's literally telling me to ignore either one, never combine the two and instead just pick one!!!
My God...so having caughed up the extra cash for a better engineering solution I get to pick the fashion in which I will grenade the motor? (yes, I'm overplaying this, but holy [censored], all of a sudden I miss my stock rods with the ARP wavelock bolts and a simpleton 48 ft-lbs of torque LOL):
1) pick the 75 ft-lbs and never mind that only stretches the bolt to 0.00051 and from an engineering perspective doesn't put it into a state where the bolt will be impart enough clamping force to deal with the dynamics of engine operation???
2) Or on the other hand ignore the measure of torque being applied to a bolt and just bloody yank on the thing until I see the bolt-stretch I aim to see???
....somebody shoot me now!!! LOL
