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Discussion Starter #1
ok guy's,I'm trying to help out a buddy thats not on the forums. he's trying to build his own sbc for his jet boat. He's not stupid ,but he's not an engine builder. he's broken 4 NEW scat (arp) rod bolts. he claims torque spec is 45 pounds,he's breaking them @ 40.says he's using there lube,checked his wrench with another. he has another set of bolts coming,he thinks its a bad batch of bolts . i don't think so .he's got to be doing something wrong. any ideas to help a brother out
 

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Resident Ford Nut
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the bolts are snapping ?

Not at 45 lbs ft......either a bad trq wrench or bad bolts....


S CP
 

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Discussion Starter #3
that was my reaction too, really snaped at 45 pounds,no way. he's checked the wrench. he thinks bad bolts. but 4 of them?? have the builders seem this before?
 

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ok guy's,I'm trying to help out a buddy thats not on the forums. he's trying to build his own sbc for his jet boat. He's not stupid ,but he's not an engine builder. he's broken 4 NEW scat (arp) rod bolts. he claims torque spec is 45 pounds,he's breaking them @ 40.says he's using there lube,checked his wrench with another. he has another set of bolts coming,he thinks its a bad batch of bolts . i don't think so .he's got to be doing something wrong. any ideas to help a brother out
Okay are they scat bolts or ARP bolts??????
 

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Red Blooded American
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Without knowing the specifics under which these bolts are failing I would have to ask a few questions:
* Was anyone measuring stretch? (I saw this already mentioned but saw no response)
* Was the torque wrench fully operational? (a trained mechanic would surely have known when they were pulling more than 40 lbs.)

Also, a rod bolt that cannot withstand 40 lbs of torque will never withstand 6000+ RPM. I'm thinking something very wrong is going on. I'd blame the bolts first and question the quality of them and maybe the authenticity of the ARP stamps. Knock-offs come in all industries.
 

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Without knowing the specifics under which these bolts are failing I would have to ask a few questions:
* Was anyone measuring stretch? (I saw this already mentioned but saw no response)
* Was the torque wrench fully operational? (a trained mechanic would surely have known when they were pulling more than 40 lbs.)

Also, a rod bolt that cannot withstand 40 lbs of torque will never withstand 6000+ RPM. I'm thinking something very wrong is going on. I'd blame the bolts first and question the quality of them and maybe the authenticity of the ARP stamps. Knock-offs come in all industries.
I will agree 110%! As I stated the stamping looks alot different than the ones on my sons new eagle h-beam rods! And also the post about how they seat makes alot of sense to me! M reread post 5
 

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Discussion Starter #13
i fully agree. I also thought about the integraty of the bolts performing:))eek:)) , a grade 5 bolt from the hardware store should take 40 pounds. i'll make these suggestions to him, lend him my torque wrench.
how should he measure stretch at this point, and what should he be looking for.
 

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i fully agree. I also thought about the integraty of the bolts performing:))eek:)) , a grade 5 bolt from the hardware store should take 40 pounds. i'll make these suggestions to him, lend him my torque wrench.
how should he measure stretch at this point, and what should he be looking for.
Is the engine at an assemble form and breaking the bolts prior to a final? does he own or know how to use a dial indicator? Not meant to be insulting but is he willing to disassemble the short block to check all this shit out? I would like to see a pic of the rods from a side shot to see how the bolts are seating on the cap. I personally think that bolt stretch is just a few steps away from curing the original problem. M
 

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45 lbs seems low even for a good 3/8" bolt. Been a while since I did any small block stuff, but I wanna say the strech for a steel H beam rod was around .0055" and it was around 70 lbs. In our current BBC steel rod motors, we use 7/16" bolts, the streach measurment is around .0065" mils and it takes about 80-90 lbs to do that.... Somethings wrong for sure...
 

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45 lbs seems low even for a good 3/8" bolt. Been a while since I did any small block stuff, but I wanna say the strech for a steel H beam rod was around .0055" and it was around 70 lbs. In our current BBC steel rod motors, we use 7/16" bolts, the streach measurment is around .0065" mils and it takes about 80-90 lbs to do that.... Somethings wrong for sure...
Scat's spec for those specific bolts is 45 ft/lbs. ARP's "general" recommendation for a 3/8" 200,000psi bolt is 50 ft/lbs.

I'd like to know where the bolt's are breaking, as that may well tell why they're breaking.
 

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Discussion Starter #17
thanks for all the input. His attitude right now is "I;ll try more new bolts". I'm the one saying somethings wrong:no:, even if he gets them to tighten to 40 or 45 #s ,i don't want to go far from the ramp,eh:angry: I'll try to talk to him & check these idea's out. the blue boat is the one in question,there's got to be an answer:secret:
 

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thanks for all the input. His attitude right now is "I;ll try more new bolts". I'm the one saying somethings wrong:no:, even if he gets them to tighten to 40 or 45 #s ,i don't want to go far from the ramp,eh:angry: I'll try to talk to him & check these idea's out. the blue boat is the one in question,there's got to be an answer:secret:
What the heck! WHEN it blows up it's only money right? Listen to everthing people here have told you, you can buy a rod bolt stretch gauge from almost any performance outlet for about $50. MAKE SURE everything is correct before you blame the bolts.

Also please post a pic of a broken bolt...

Just for interest sakes I had a friend who while assembling his SBC torqued the factory 3/8" bolts and nuts to 75 ft/lbs by mistake... they stretched almost 1/8" yet didnt break... so something is drastically wrong to break a bolt @ 45 ft/lbs
 

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Some guy
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thanks for all the input. His attitude right now is "I;ll try more new bolts". I'm the one saying somethings wrong:no:, even if he gets them to tighten to 40 or 45 #s ,i don't want to go far from the ramp,eh:angry: I'll try to talk to him & check these idea's out. the blue boat is the one in question,there's got to be an answer
If you are going over there anyway,, maybe you can torque one yourself, or hand him your wrench and watch him pull on it. 45 ft lbs with a 1/2" drive torque wrench should be able to do with one finger. If he is pulling the wrench real fast, he may get way past 45 lbs?

One other thought,, he couldn't have the wrench set at 45KG instead of lbs?
 

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You're very first give away that something is really screwed up here is that the rods come with the bolts torqued to spec. If the bolt took 45 lbs once, it would be hard to imagine it breaking at 40 the next time.

I have deiliberately taken a USED ARP bolt in a bad rod using ARP lube and tightened it till it snapped just to see what one will take, and I assure you its well beyond the torque spec.
Normal torque is about 85% of yield which well below failure. Yield is simply the point where the bolts unload length is permanetly changed. Failure is well beyond that.



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