How to; Stretch Guage Video

[jamesjedi]

I am not sure if this would help anyone who is going to be bolting their ARP connecting rod bolts, or for that matter, I do not even know if he does it correctly. Anyways, have a look and tell me if it looks correct?

If it is correct, perhaps it could help someone like myself who will be doing this very soon.


http://www.lowbugget.com/Produce_1.wmv


Thanks.

[Ken911]

any one know hoe to get individual bolts? If you over stretch one and need to replace it? All the places i checked only sell sets of 12.

[KTL]

Note that the bolts he's using are not like stock Porsche rod bolts. The rods here are aftermarket non-OEM type that have a tooled head for a wrench and threaded rod caps. Porsche OEM bolts have a flat that rests against the rod body to counterhold the rod bolt while tightening- no wrench on the head required. The Porsche caps are not threaded, so the rod bolt uses a nut. Nice thing about the OEM type bolts for stock Porsche rods, you only have to be concerned with the bolt itself being fully inserted into the rod body. No need to worry about the lube under the head. Only the shank & threads are important.

The OEM bolt shank aligns the rod body to the cap, so it must be allowed to slip into the body and the cap very cleanly. Then the threads and nut are the part of the bolt that experience the most movement. However, don't forget that the shank still must be able to slide within the rod body and cap, in order to stretch. So lube on the shank is still important!

The problem I see is he's using a cheap torque wrench...... That's the Craftsman Digitork wrench and he's also using it to loosen the bolt. Common instructions for any decent torque wrench will say NOT to load the wrench in reverse.

But the check for stretch is correct from what I can gather based on the bolt he's using. The burnishing of the threads and shank by torquing and releasing the bolt with a partial torque amount is indeed a recommended procedure to run-in the bolt threads to the rod cap threads and also run-in the bolt shank and bolt flange to the rod body. Since the bolt in this case is spinning and bearing on the rod body (via the flange of the bolt), spinning in the rod body (shank) and in the cap (threads), the run-in helps normalize the reading you'll get.

However, note at the very end he says his procedure is only for checking if the bolts are good/bad. Point being is, the procedure he's using isn't for permanently installing the bolts. It looks like he's using an aftermarket rod. For instance, Pauter recommends you incrementally torque the bolts to ensure uniform clamping of the cap to the rod body. BlockNotch

This is because Pauter rods have an alignment sleeve that aligns the cap with the body. The bolt shank is not used to align the cap and body. Nonetheless, I would think it important to put some lube on the shank, should the clearance be tight between the shank and the bore in the cap and body.

Plus, I don't necessarily agree with his approach of choosing an arbitrary +2 ft-lbs to get the recommended stretch, and assuming torque wrench error/inaccuracy with respect to what approximate torque number is required for achieving desired stretch. He is right that a bolt requiring very low torque to reach stretch spec indicates a faulty bolt. As he said, a bit more torque than what the manufacturer specs is not out of the ordinary. I would attribute that to lube and or temperature. To choose another 2 ft-lb (or have a torque wrench that isn't accurate) might put you past the stretch.

I would think the proper anal procedure for install is to have the stretch gauge on the bolt as you apply your final torque and monitor the stretch as you apply force to the wrench. Not easy to do since the gauge sits on the bolt head or the nut, in the case of the OEM type bolts. You would need a thin, long box end wrench or crowfoot to do this. Note that with the crowfoot you have to alter your torque setting on the torque wrench.

Then you can creep up on the stretch and see the dial indicator hit your target and not go past. I will agree with him that if you find you are having to apply much more than the recommended torque, something is wrong with the lubrication.

Speaking of Pauter, note that their spec says engine oil and not ARP lube. I have a problem with that, because engine oil is a VERY general term and could produce significant differences in torque, depending on what oil you use. ARP even comments on that in their information about their lube. Is it made-up info., just to sell their lube? I don't know. But you'd think the manfacturer's lube spec'd for their bolts is going to be the most accurate, since that's what their approx. torque spec is based on. Scroll down to the part about their lube.

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Oil gets you there, but you have to cycle the bolts a number of times to do it.