Who are you going to beleive, the people that make the fasteners or ARP? YOu might ask ARP who makes their fasteners. I suspect that they do not make their own, but I really don't know.

One I do know is SPS. Check out their info, They are the ultimate fastener company.

Well that's a fine technical explanation!

Sigh...thank goodness spring is here

so where does all of this leave someone like me, a first time engine rebuilder who wants to do it right? ive got waynes book, he dont talk about stretching anything other than my wallet with all the things that i forgot that i would need when rebuilding my engine! i thought that by buying the upgraded bolts that i was covering a faliure in that area and that if propoerly tourqued and not defective, that would be it. what did the factory do, stretch measure all their bolts?

Adomakin m8,

You're just fine to torque to the specs on the ARP sheet. This will put you in the safety factor range. I know plenty of folks who have done just that. Chris Streit is one of them and you should see how he abuses his engine. Plus ARP would not suggest this if it were unsafe EVEN if the marketing folks wanted to.

talking of bolts, ARP or RACEWARE?

Great point. We can propose all the technical arguments we want, but it's all defenestrated when the part is defective.

HOORAY HURRAH BRAVO!!!

http://www.pelicanparts.com/support/smileys/wat6.gif

Actually the opposite is true, but what the heck. In any case its also best to retighten rod bolts as few times as possible, and in the case of factory bolts only once.

And for marketing people--- Know how to tell a salesman is lying? His lips are moving.

Hey wait... I'm a salesman....

Jack,

ARP recomends torqueing them 3 times before use. Tristan was on his 2nd round when he luckily discovered this defect.

I am really interested in hearing ARP's story behind these defective rod bolts. I used them, torque method, and so far so good, but it makes me wonder what their failure rate per thousand is...


ADOMAKIN, either are appropriate, I've never heard one was better than the other. I think Raceware are priced quite a bit higher though!

After seeing what happened to Tristan, I don't need no science to tell me the obvious conclusion.

IF he had used the stretch method on the defective bolt, it may very well have stretched to the "appropriate value" before reaching a clamping value enough to withstand the forces of the engine.

Since it stretched too much, it is reasonable to assume that the bolt was weak, but the stretch method would not have shown this defect.

So realistically I think the best approach is probably BOTH methods. Stretch to verify proper clamping force, with the understanding that a good bolt will reach a reasonable value within a torque range.

So if the bolt that should be in a torque range of 43-48 pounds (which is probably as accurate as most wreeches get) when it is stretched by the indicated value. AND if you've reached the indicated stretch value but have only applied about 30 pounds of torque, something just ain't right. That's what I did, that's what Tristan did.

Disagree? Then tell me how the stretch method alone would have shown this defect...

I can't find any info of SPS rod bolts on their website.... They have several different types of bolts like Unbrako etc. Which type is correct? And what's the part # for 10mm size?

cheers cstreit, ARP its gonna be!

I just watched a guy strip out a whole bunch of head bolts on a Big block chevy. Turns out the torque wrench was way out of calibration. Unless your dial indicator is "Way out of whack" you will not experience this problem using the stretch method. As to the stretch method not detecting a bad bolt and the torque method being somehow superior, TOTALLY BOGUS INFO. A good bolt is 100% xrayed, there is NO other way to guarentee you have a good bolt. Are ARP bolts xrayed? NO they are not, thats why they are so cheep. A good rod bolt is at least $20.00 ea, any other is a bet, just a bet that it is good, not a guarentee.

Good rod bolts go with good rods, ie Carillo. The ONLY rods used by serious racers. Special threads are required to properly utilize these bolts, and specially designed rods are required to accept them.

Don't take me wrong, both ARP and Raceware make a bolt that is probably better than the original Porsche ones, but think about it, Porsche spends a lot of money to make one of the best sports cars on the road. Just how much are they really skimping on the rod bolts? As to racing, any serious racer uses Carillo, period. If you are spending $50K plus on an engine are you going to go for a savings of say $200 to $400 total on some off brand rods and bolts? Not likely if your are smart. Just one of the reasons you do not see a lot of engines blowing up in professional races.

For more info on SPS try http://www.spstech.com/aero/prod_lit/index.html

For referance the best ARP/raceware rod bots is between 180,000 and 220,000 psi, a properly designed sps fastener in a Carillo rod is approx 320,000 psi, a very big difference, and its guarenteed, not "hoped for" performance.

so its ok for me to use ARPs for a mild tuned turbo street engine then?

Absolutely. But I would spend the $80 bucks or so required to properly measure the stretch of these bolts. Otherwise you may not get what you paid for.

And if your real cheep, like me, you could just turn the nut an eight of a turn at a time and check it with a micrometer each time, May thake a day or two to do a two minute job, but its cheeper.

so are you measuring from the head of the bolt to the tip of the bolt thats exposed at the other end?

I just don't get it Jack. First you take a holier-than-thou attitude to my question. And I doubt you have a degree in engineering or you would have understood my argument about safety factors and why I believe I'm "in the zone just by torquing". You'd also understand that cycling a fastener like ARP through multiple stresses with your torque wrench won't do the bolt any harm if you are in the elastic zone of tensile strain (there's an argument for the threads not surviving too much of this). WHY? Because steel has practically an infinite fatigue life IF kept under the fatigue life limit which I'm willing to bet ARP's bolts are designed to. Then you turn this thread into a VENDOR debate between SPS and ARP which is probably overkill for street purposes. You have folks all paranoid about a bolt that's over engineered for any street track application (unless you're building a monster high rpm motor). THEN after ALL of that you turn around and say that you are "cheep" [sic] and you don't use a stretch gauge after all because you were having us all on and you actually use your micrometer and measure after each incremental turn of the wrench!

Jack - you're making my head hurt. Move on, you're tiring us.

Tristan

Dang! I love it when it gets hot...so I have to throw in my two cents..

If Tristan's torque wrench is off (it would have to be a lot) why didn't the other bolts fail? It seems to be a simple issue of some bad bolts.

I would love to visit a shop that does 100% x-ray testing on every bolt that comes off the line. If there is such a shop, I would love to see how they do it. Even with the great "Six-sigma" hype in QC, you won't find a shop that x-rays 100% of the parts.

Any of the processes in the manufacturing of the bolts can cause a defect and since the QC checks are random samplings, some bad batches get out. A random part(s)/bolt(s) that was tested from that batch may not have failed the test(s), so that batch gets out. Even the test may not be perfect. (I have performed lab testing of bolt and metal failure, and the results never gave me the confidence that I could predict when and how a bolt will fail...at least not with 100% confidence!)

I've had bolts fail in the field after all the testing and all the QC by the manufacturer. The bolts are used to hold 1500+ psig of pressure on a pipeline. You can bet that the bolts were under a QC program. But the real world is not perfect and defective parts make it out to the field.

Jack has some good things to say now and then so I peruse his posts for the good stuff, but I don't think Jack's thinking broadly enough here.

And serious racers don't have to spend $50,000 on an engine, just the ones with lots of money or a fat sponsor :)

Just when I thought this thread was over...the Soukmeister comes into play :)

About the comment with carillo being all hail and mighty, what about pauter? Not competing, just curious of the comparison, since i don't know where you guys find these stats.
Also, it says in arp's website that their rod bolt material has a tensile strength of 255,000 psi.