DraggingDatsun Posted January 13, 2012 Share Posted January 13, 2012 Putting my winter l28et with a 50trim t3/t4 running 10psi beater back together and just put in new bearings, arp rod bolts, arp head studs, and new gaskets all in it because it spun some bearings so its all ready to go back together but I am out of money and I know I should replace the main studs but am out of money is it strictly necessary to replace or can I reuse the oem ones?? Quote Link to comment Share on other sites More sharing options...
RB240zDET Posted January 13, 2012 Share Posted January 13, 2012 I wouldn't. You just spent all that money on fixing/building the engine and you are risking it all on the main studs. There is a guy selling a set of brand new main studs on Zilvia for 110shipped I believe. Let me find the ad for you. Quote Link to comment Share on other sites More sharing options...
RB240zDET Posted January 13, 2012 Share Posted January 13, 2012 http://zilvia.net/f/sale-items/426530-l24-l26-l28-arp-main-studs-brand-new-100-shipped.html Quote Link to comment Share on other sites More sharing options...
DraggingDatsun Posted January 13, 2012 Author Share Posted January 13, 2012 cheaper on ebay thanks for the post tho. I was thinking about buying main studs and not the head studs, and just use the oem ones I just took out. Then as soon as I can afford head studs buy those and swap them one at a time with out taking off the head so not to mess with the head gasket. Quote Link to comment Share on other sites More sharing options...
RB240zDET Posted January 13, 2012 Share Posted January 13, 2012 Every time you torque down the studs you are 'stretching' the stud and thus after the first time you are going to be getting a inaccurate torque and overall weakening the stud. So to reuse them is a risk and a matter of time before one of them snaps. Overall I would not risk it. Especially considering how cheap they are to replace. Quote Link to comment Share on other sites More sharing options...
DraggingDatsun Posted January 13, 2012 Author Share Posted January 13, 2012 poor college student lol Quote Link to comment Share on other sites More sharing options...
RB240zDET Posted January 13, 2012 Share Posted January 13, 2012 poor college student lol Sell some Z parts then. Do what you gotta do, but honestly do not risk throwing all that money down the drain on reusing old main studs. Quote Link to comment Share on other sites More sharing options...
surpip Posted January 13, 2012 Share Posted January 13, 2012 (edited) Agreed, its cheap insurance. Edited January 13, 2012 by surpip Quote Link to comment Share on other sites More sharing options...
Lazeum Posted January 13, 2012 Share Posted January 13, 2012 (edited) Every time you torque down the studs you are 'stretching' the stud and thus after the first time you are going to be getting a inaccurate torque and overall weakening the stud. So to reuse them is a risk and a matter of time before one of them snaps. Overall I would not risk it. Especially considering how cheap they are to replace. I don't think what you've stated is right: those studs (like rod studs & head bolts) should never be stretched past elastic/yield strength. If you tighten them past elastic mode, there're going to snap them under load & inertia from pistons since there're going to be in plastic mode. So those bolts are reusable since you should never go beyond critical stress on those. However, I come to the same conclusion as you do: it is cheap insurance. I did not do it however on my rebuild, I only did rods (notorious from being the weakest link in the bottom end) & head studs. Edited January 13, 2012 by Lazeum Quote Link to comment Share on other sites More sharing options...
Leon Posted January 14, 2012 Share Posted January 14, 2012 I don't think what you've stated is right: those studs (like rod studs & head bolts) should never be stretched past elastic/yield strength. If you tighten them past elastic mode, there're going to snap them under load & inertia from pistons since there're going to be in plastic mode. So those bolts are reusable since you should never go beyond critical stress on those. However, I come to the same conclusion as you do: it is cheap insurance. I did not do it however on my rebuild, I only did rods (notorious from being the weakest link in the bottom end) & head studs. Exactly. These are not "torque-to-yield" fasteners. They are reusable if you have not over-torqued, and if they haven't fatigued. Would you rather quantify these, or just buy new ones? I'd get new ones. Quote Link to comment Share on other sites More sharing options...
RB240zDET Posted January 14, 2012 Share Posted January 14, 2012 Exactly. These are not "torque-to-yield" fasteners. They are reusable if you have not over-torqued, and if they haven't fatigued. Would you rather quantify these, or just buy new ones? I'd get new ones. Not a matter of torque to yield. My point is any time you torque a bolt down you are theoretically stretching the bolt to achieve the desired torque setting. It may be minimal but my point is on something that is as essential to an engine as a head stud, main stud, rod bolts, etc you should not really reuse any of the original hardware. Quote Link to comment Share on other sites More sharing options...
Leon Posted January 14, 2012 Share Posted January 14, 2012 Not a matter of torque to yield. My point is any time you torque a bolt down you are theoretically stretching the bolt to achieve the desired torque setting. It may be minimal but my point is on something that is as essential to an engine as a head stud, main stud, rod bolts, etc you should not really reuse any of the original hardware. It is very much a matter of torque to yield. When you torque down the bolt, it does stretch. However, if you don't reach the yield point of the material, then it returns to the same state when loosened. The bolt stretches and then goes back to its original length, as long as you stay within the elastic limit of the material. Another consideration I've mentioned is bolt fatigue. If the OP plans to reuse the bolts, then a close visual inspection must be done paying special attention to local cross-section diameters. Like I said, I would rather just buy new studs and be done, however, if done right then the old ones may possibly be reused. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted January 14, 2012 Share Posted January 14, 2012 (edited) My current engine has reused the rod and head bolts through 3 different configuration changes and engine installations in multiple cars for about 10 years. That doesn't mean someone else won't have a rod bolt break 1 week after replacing rod bearings but reusing the bolts on his pristine 1983 ZX with 83k miles on the clock. I've also seen someone actually put 65 foot pounds on the rod bearings and only stopped because the 9th bolt he torqued started stretching and he checked to find he was using the wrong torque. For a LD28, replacing rod bolts with ARP is a no brainer as well as a high HP or high RPM driven car. Edited January 14, 2012 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
DraggingDatsun Posted January 14, 2012 Author Share Posted January 14, 2012 Thank you guys very much so what is the final vote I need to get my car back on the road to get to school in this bs winter weather should I reuse the main studs or the head studs? Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 14, 2012 Share Posted January 14, 2012 I counted three for buy new, and two "do it if you have the money". But there were also two good materials science based explanations of why you should be able to reuse them, and one real-world example of reuse. Also, $110 is not much money to some. The "relativity theory" of car hobbies demonstrated. What are you studying in college? Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 15, 2012 Share Posted January 15, 2012 RB240 is barking up the wrong tree with the "stretching" argument. None of the fasteners are, as stated "torque to yield" and therefore technically possible to be reused (THE NOTABLE EXCEPTION IS ROD NOLTS, they are stretched during tightening and are operation critical due to cyclic loading, and should NE replaced each time, or replaced with reusable fasteners like 396 Chevy or ARP's) The reason they are called out for replacement is "burnishing"---the threads in the block are burnished each time a fastener is installed in it. Same for the bolt (it's a bolt, not a stud, design applications are different!) What you design a fastener for is between 75-80% of tensile strength. How do you get this? Torque the bolt right? WRONG! Torque is only an APPROXIMATION of tensile loading. This approximation takes underhead and thread friction into account. These two frictional losses account to nearly 85% of the torque you read on the wrench. ANY change in the friction on the threads can directly return that much more tensile loading of the fastener. On high stress fasteners like head bolts this can mean putting the fastener into the plastic deformation phase from merely being loaded to 80% of tensile. This inconsistency in USED fasteners is why they call for new to be used. A new fastener will thread up the same every time, and the margin of improvement from burnishing of the shreds is only confined to the block, which in this case will not bring the fastener into this range of deformation. If you will notice, ARP calls for new nuts and specific lubricants to be used... Know why now? Take a bolt and run it into a tapped hole with some lube on it, go all Yhe way in. Then remove it, clean both and relubd and repeat. Each time that fastener will go in easier and easier. This is what they are trying to counteract. Www.boltscience.com is a good site to go to and learn more about fasteners, washers, and bolted joint design. Reading the case studies there is fascinating, even counterintuitive in some cases. Their little talk about roadwheels and lugnuts is especially enlightening! Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 15, 2012 Share Posted January 15, 2012 Neither BOLT you have will really matter. I'd put head STUDS in to replace the current BOLTS as your thought on saving the head gasket is not likely to pan out in action. You can redo the bottom end with STUDS when the engine comes out again. The main reason to put STUDS is you are into the engine repeatedly for freshening. There is far more chance you will have the head off before you have to go into the bottom end again. Quote Link to comment Share on other sites More sharing options...
clarkspeed Posted January 18, 2012 Share Posted January 18, 2012 Yes torquing of fasteners is so critical but still an approximation at best. These are some methods NASA uses to narrow the variability and prevent yield: 1. Measuring the stretch. Typically used on large critical fasteners that are reused. 2. Measuring the running torque with a dial torque wrench. This number is then added back to the tightening torque to calculate the final torque value. Typically used when fasteners have a locking feature or interference incorporated into the design. 3. All new hardware with specified lubricant. I believe all flight fasteners are designed around one or more of these 3 methods. Quote Link to comment Share on other sites More sharing options...
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