How many times can rod and main bolts be torqued?

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DartVadar

DartVadar

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As I am about to get ready to put my 360 back together I just had the thought about how many times I can torque some of the bolts. Specifically the rod bolts, mains and head bolts.

The head bolts are ARP bolts, and they have been torqued twice, the rod studs are ARP as well and have been torqued twice. The mains are the stock bolts, and if you include when the motor was put together in 81 and when I put it together last time they have been torqued twice.

Should I get some new bolts? or will I be fine with re-using them?
 
I wouldnt dream of using those rod bolts over twice, they stretch at least .020 each time just at 35 ish ft. pounds of torque. Stretch = fatigue, fatigue = booooom !!!
 
What he said ^^^^^. PLUS there's this. Think of how much inertia is put on the rod bolts with each engine revolution. Think of race cars in the staging lanes and how they rev the engines to clear them out before a race. Now, imagine the rod bolts having to hold all that together. The rod bolts actually stretch and rebound ever so slightly with each revolution. In other words, they HAVE a service life! This is why I REFUSE to do an engine job if someone does not want to pay for new good quality rod bolts and at least reconditioning the rods. It's that important.
 
Can see its probably a good plan to replace them then.

Now how do I go about doing that? Last time I got them installed they re-sized the rods, does that have to be done again? Or is it just a matter of simply taking the old ones out and pressing in new ones?
 
The rod bolts would concern me the most. Especially if you plan on running this engine hard. Sound like you're looking at X3 on all of these. The ARP head & stock mains "may" be ok... I've done two times on both, and will admit I did cheat a little on the specs, meaning 3 to 5 lbs. more without a issue. As far as the rods, can you call someone at ARP and get a recommendation?

Lets face it, new is better. And keep in mind, the big ends will have to be checked with a bolt replacement. Not saying not to do it, just letting you know there may be a little extra cost involved.
 
Yes. The rods need to be resized when the rod bolts are replaced. I have seen some disagree, but IMO it is imperative. Think of all that's at stake. Nuff said.
 
Well I guess I'll have to get that done again then. But what changes by just changing the bolts out? why do they have to be re-sized?
 
Think of the oil clearance between the rod bearings and journals. You're talking on the order of .0015"-.002". The rod bolts are either pressed out or gently knocked out with a brass hammer. Either procedure can tweak the big end of the rod. Also, minute differences in the rod bolts diameters will place the rod caps in an ever so slightly different place than the old rod bolts. When you're talking about thousandths of an inch clearances, the least little change can be a big one.
 
Round, Round, Round!

The slightest distortion can throw things out of wack. Might not be bad at all, but you must have them verified and reworked if needed.
 
Thats true, never thought of it that way. Well I'll take everything in tomorrow to get done.

And I may just replace the head bolts, but the main bolts, I've just seen stud kits, not really bolts that just drop in, or am I wrong?
 
ARP makes both bolts and studs for the mains.
 
Ill look into those then.

But is there actually a amount of times they can be torqued? because you torque them to check bearing clearances, and then once again to assemble it, I'm reading that Arp recommends torquing them a few times to get everything seated and ready for the final torquing, dont know how reliable that is though.
 
Torqueing them and torqueing and then running them are two distinctly different things. As for main and head bolts, I prefer not to use them more than three or four times. You might contact ARP and see exactly what they say there.
 
That makes sense, well the rod bolts have only been ran once, but torqued twice. For the cost savings it's not worth it if something goes wrong, so I'll just get new bolts and re-size the rods.
 
Our rule of thumb was no more than 5 clamp cycles on bolts or they need to be replaced. We "saved" 2 cycles for service, one for a repair, one for a rebuild.

Now keep in mind that when we machined the rod and cap together, that was the first clamp cycle on the bolts.

Then on the engine line, we had to split the rod and cap to install the engine, which was clamp cycle #2.

This left us one repair on the engine line or one time to recycle the pistons if we had to tear down and recycle the parts for clamp cycle #3.

Like I said, we saved two clamp loads for service.
 
RustyRatRod said:
Yes. The rods need to be resized when the rod bolts are replaced. I have seen some disagree, but IMO it is imperative. Think of all that's at stake. Nuff said.
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Yes, if you replace the rod bolt, it's best to have the crank bore refinished as replacing the bolts can make the cap fit differently to the rod. any mis-match can cause the drag on the crank up to locking it up completely.
 
the67fish said:
I wouldnt dream of using those rod bolts over twice, they stretch at least .020 each time just at 35 ish ft. pounds of torque. Stretch = fatigue, fatigue = booooom !!!
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I think that you are off a bit on the stretch.


Most rod bolts permanently stretch .001" - .003" per clamp cycle. I have done bolt stretch studies.
 
krazykuda said:
I think that you are off a bit on the stretch.


Most rod bolts permanently stretch .001" - .003" per clamp cycle. I have done bolt stretch studies.
Click to expand...

Karl: those last three posts,are honest & correct . (for, where I learned.)
 
krazykuda said:
Yes, if you replace the rod bolt, it's best to have the crank bore refinished as replacing the bolts can make the cap fit differently to the rod. any mis-match can cause the drag on the crank up to locking it up completely.
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Crank bore refinished? Wouldn't I have already had that issue when they were re-sized already? Because everything got pretty good.
 
From ARP catalog:
Are ARP bolts and studs re-usable?Yes. As long as the fasteners have been installed and torqued correctly, and show no visible signs of damage, they can be re-used. If they show any signs of thread galling or corrosion, they should be replaced. In the case of rod bolts, if any of them have taken a permanent set and have stretched by .001” or longer, you should replace them immediately. See page 29 in the catalog for more detailed information on this critical measurement.
Here's page 29:
http://arpcatalog.com/?src=home#29/z
 
69_340_GTS said:
From ARP catalog:
Are ARP bolts and studs re-usable?Yes. As long as the fasteners have been installed and torqued correctly, and show no visible signs of damage, they can be re-used. If they show any signs of thread galling or corrosion, they should be replaced. In the case of rod bolts, if any of them have taken a permanent set and have stretched by .001” or longer, you should replace them immediately. See page 29 in the catalog for more detailed information on this critical measurement.
Here's page 29:
http://arpcatalog.com/?src=home#29/z
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Are you crazy? Why would you contact the manufacturer and experts when you can go with the "wisdom" of the internet? ;-)
 
66fs said:
Are you crazy? Why would you contact the manufacturer and experts when you can go with the "wisdom" of the internet? ;-)
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Exactly why I recommended he contact ARP in post #13, but of course since I said it, it was ignored. lol
 
Rusty-We do listen to you,Your straight answers and opinions in all Mopar matters are outstanding,Don't give up on us,a lot of us just don't comment much but we ALL read--Steve
 
RustyRatRod said:
Exactly why I recommended he contact ARP in post #13, but of course since I said it, it was ignored. lol
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I know you did. If I knew I had ARP rod bolts, I'd call them first. The thing to remember about bolts and studs, is they are just real stiff springs. Once you go past yield they are compromised and should be replaced. The trick is, did DartVader measure and record the measurements when he first assembled the engine? And while we're talking about design here, "fatigue" is not the same as torqueing a bolt 2, 3, or 10 times. It is thousands of cycles and is also a strength known for certain materials.
 
66fs said:
I know you did. If I knew I had ARP rod bolts, I'd call them first. The thing to remember about bolts and studs, is they are just real stiff springs. Once you go past yield they are compromised and should be replaced. The trick is, did DartVader measure and record the measurements when he first assembled the engine? And while we're talking about design here, "fatigue" is not the same as torqueing a bolt 2, 3, or 10 times. It is thousands of cycles and is also a strength known for certain materials.
Click to expand...

Exactly. Much like I described the action of the rod bolts stretching with every RPM cycle. It does not matter whose rod bolt you use. They all have a shelf life.

What gets me is, how many people do an old dirt road build and actually get by re-using rod bolts with 100K plus miles on them. I would do that and sling a rod into next week.
 
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