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Originally Posted by mike tkach
(Post 4385745)
joe,good question.if you removed the 8740 bolts from dan,s rods and installed arp2000 and torqued to spec the housing bore would no longer be round and would need to be shaved&re honed.i also forgot to mention earlier that arp,s recomended stretch is 75% of total yield,they do this because if you over stretch a rod bolt it is rendered useless.this is why some rod makers show different stretch value,but it is still in arp,s spec if that makes ant sence.guess i should mention,total yield is the point that a rod bolt will brake when over stretched.also,the tighter a bolt is torqued the more clamping load it exerts.
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a bolt is like a spring,if it does not return to it,s initial length after it is stretched it is time to replace it.this is a simple way to describe a bolt.i am not always so good with words so my explination sometimes gets confusing.
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Mike, You share some Great Info on here. I have been an engine builder since 1987. I am still always learning new stuff. Others do as well. Thanks foe the honest info. "My 2 cents", I like Oliver and Carillo Rods the best. But most customers won't go the cash for either set. In recent years I have had better luck with Eagle and Manley out of the box. They all need to be sized to the exact build application though. Both Ends.
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Ok. Having never assembled an engine. Torque spec I get and is obvious. How do you know/measure of the bolt has been properly stretched. I'm assuming a mic however if as Mike put it, it acts as a spring you'd have to remove the bolt for that measurement and it would no longer be stretched. Pardon my ignorance on this particular subject.
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stretch gauge, if you look at the bolt there is little divots at each end for that gauge to attach to.
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Originally Posted by I.C.U.Lookin
(Post 4385972)
Ok. Having never assembled an engine. Torque spec I get and is obvious. How do you know/measure of the bolt has been properly stretched. I'm assuming a mic however if as Mike put it, it acts as a spring you'd have to remove the bolt for that measurement and it would no longer be stretched. Pardon my ignorance on this particular subject.
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Got it. Makes sense now. Thanks.
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Anytime....
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Originally Posted by horsepower1
(Post 4385758)
This is why when you use the stretch method, you should keep a log of the bolt lengths. Measure before installation and then when you remove them for a re-build or whatever. If any of the bolts have a free length of more than .001" than before, then they need to be replaced because they have exceeded their elastic limit (yield strength) resulting in deformation of unengaged thread. The bolt is junk. Yield is different than ultimate tensile strength (UTS). UTS is where the bolt will break, yield is where it exceeds it's elastic limit and deforms. I will also say it is far worse to under tighten a critical bolt than properly tighten one.
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Originally Posted by 29 FOUNTAIN FUN
(Post 4385956)
Mike, You share some Great Info on here. I have been an engine builder since 1987. I am still always learning new stuff. Others do as well. Thanks foe the honest info. "My 2 cents", I like Oliver and Carillo Rods the best. But most customers won't go the cash for either set. In recent years I have had better luck with Eagle and Manley out of the box. They all need to be sized to the exact build application though. Both Ends.
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Originally Posted by mike tkach
(Post 4385732)
EDIT IN,i just finished a 565 that got new callies ultra rods,callies already torques&retorques the rods before shipping so the end user does not need to.this is stated in the directions they come with.ps,they come with arp2000 and it also sais callies on the bolt.
This may the case with MOLNAR ??, them bolts are super tight!! ( only took one out to compare) |
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