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when using rod bolt stretch gauge do you do one bolt at a time?

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when using rod bolt stretch gauge do you do one bolt at a time?

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Old 04-07-2013, 07:26 AM
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Default when using rod bolt stretch gauge do you do one bolt at a time?

Quick question on using a rod bolt stretch gauge. In the past when I just torqued my rod bolts with a torque wrench, I always torqued each bolt on the rod sequentially in steps of about 25 ft lbs, to even out the pull. I don't really see a way you can do this with a stretch gauge, unless you stretch a couple of thousandths on each side and move the gauge back and forth - or you have two gauges. Does it hurt anything to stretch each bolt to the full spec? Of course, I am going ahead and torqueing to spec (63 ft lbs) a couple of times to seat the threads and the rod caps first.

Appreciate any input.

Thanks!
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Old 04-07-2013, 11:26 AM
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Originally Posted by Budman II View Post
Quick question on using a rod bolt stretch gauge. In the past when I just torqued my rod bolts with a torque wrench, I always torqued each bolt on the rod sequentially in steps of about 25 ft lbs, to even out the pull. I don't really see a way you can do this with a stretch gauge, unless you stretch a couple of thousandths on each side and move the gauge back and forth - or you have two gauges. Does it hurt anything to stretch each bolt to the full spec? Of course, I am going ahead and torqueing to spec (63 ft lbs) a couple of times to seat the threads and the rod caps first.

Appreciate any input.

Thanks!
pre stretch them in a rod vise first..i do them all then leave them sit over night then loosen them and follow the rod torqur recomendations..you just need to stretch them for the intional build so the bolts stretch them selves under power and fall apart..somw may do it another way but i have never had a problem and i wind mine up to 6k..
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Old 04-07-2013, 12:52 PM
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Fixx, the way I understand it, the bolts are supposed to be stretched a set amount to achieve the proper preload on the fastener. Too loose and the fastener could be stretched an additional amount under load and come loose and fail, stretched too much and it loses its ability to "snap back" - like a spring, and will likewise fail. Never really heard about them having to be "pre-stretched". I have read that ARP suggests torquing them several times so that the threads and the heads of the bolts "burnish in" to make the torque readings consistent. The stretch gauge negates the effect of friction on the fastener.
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Old 04-07-2013, 01:09 PM
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I did a little digging, and found the following article that explains it pretty well. According to this article, I may want to consider torquing the opposing bolt to around 25 ft lbs to give it a little preload and ensure that it is fully seated. The install the stretch gauge. Not sure if I would have much luck achieving repeatability if I remove and reinstall the gauge without zeroing the dial each time. I saw another thread that said the folks at Oliver recommended dulling the point on the stretch gauge to help it seat in the dimples on the rod bolts more consistently.

Article => http://performanceenginetech.com/con...tch-vs-torque/
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Old 04-07-2013, 01:19 PM
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Yes do half the tq spec on both bolts then use the stretch gauge.
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Old 04-07-2013, 01:51 PM
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Originally Posted by Budman II View Post
ot sure if I would have much luck achieving repeatability if I remove and reinstall the gauge without zeroing the dial each time. I saw another thread that said the folks at Oliver recommended dulling the point on the stretch gauge to help it seat in the dimples on the rod bolts more consistently.
If the gauge's indicator isn't a POS you should be just fine. Be careful when handling the gauge, and take notes. If you drop it, bang it, etc, having good notes will allow you to go back to a bolt of known length and compare gauge readings.

Dulling the point seems like a good idea, making it easier to get consistent readings.

Never built an engine, but I've definitely measured a few things in my day.
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Old 04-07-2013, 02:07 PM
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Originally Posted by indysupra View Post
Yes do half the tq spec on both bolts then use the stretch gauge.
Indy, if I torque it to half the spec, it will stretch the bolts to some degree, and then if I further stretch the bolts to the spec (say .006) using the stretch gauge, then wouldn't I overstretch it? Sounds to me like the way to do it would be to do several passes to the specified torque (63 ft lb), then back them off to finger tight, then tighten the opposing bolt to say, half the spec, and then use the stretch gauge on the remaining bolt from a relaxed state. That way I ensure that I am measuring to full stretch from a relaxed state.
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Old 04-07-2013, 02:19 PM
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I thought that was a given sorry. You half tq both then obviously relax one then put your gauge on the move to the next one
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Old 04-07-2013, 05:21 PM
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they all come out with this new technological with pre stretch gauge which is ok but a pain in the ass.....the arp old way was to put the rod in a rod vise and over torque the bolt by 10 ftlbs then go to the recomended rod torque. Torque the bolt to the reccomended torque spec...take rod bolt gauge and measure the bolt then up the torque to achede your .008 or what ever stretch is required..

Last edited by FIXX; 04-07-2013 at 05:40 PM.
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