New fasteners on every build

I have always used new fasteners on all internal parts every time I build something.I recently got some new ring gear bolts at Summit and was thinking I just changed them 5 years ago when I put the 3.54's in.Do you guys change ring gear bolts,flywheel bolts,pressure plate bolts etc. when you have them apart? I just think it's just cheap insurance to use new top quality fasteners when you have it apart
Now I know an aircraft tech and he says sometimes it's better to know what you have instead of using new.
Do you guys use new bolts every time you change out rotating high stress parts like flywheels and ring gears?

Gus

No.
Old parts have proven themselves to be good.
New parts haven't yet...

No, I don't trust fasteners anymore, how do you know for sure where they are made? The original fasteners worked just fine, if they still look good I use them.

I toss any critical fastener previously used, be it engine, trans, rear end, suspension, braking system, a fastener can only survive just so many stretch, stress, along with heat cycles before failure...I generally prefer to increase the grade/tensile of the fastener if I can when replacing it

On this topic, I would say one of the most re torqued, without at least a torque wrench, possibly over tightened with an impact, cyclically stressed, non redundant, critical fasteners, is also one of the least replaced items on a high performance car, the wheel studs.

ARP

Gus, if it ain't broken, don't fix it
if marginal or suspect replace it with better parts

New ARP bolts inside the engine. Other less important stuff is replaced if it shows wear and tear and looks suspect.

My last engine rebuild was based from an engine that came from a van that burned to the ground so I bought all new fasteners throughout.

I don't replace bolts unless I see a problem with them. I throw bolts and nuts away if they have any damage but otherwise just clean them and put them back into service. Bolts are basically springs and we reuse springs over and over until they get damaged or lose tension.

Gus, I have changed gears in my Dana at least 5 times if not more. I am going to change them again and this time I will change out all of the bolts. May not need to but after this many times why take the chance -

Never

Absolutely spot-on...

That's what most people believe. Without any metallurgical background, of course...

Actually I have 35+ years experience in a metallurgical/engineering field

Send me all your wore out bolts, I'll get rid of them for you.

Which is the exact reason why I agreed...

Ok, so explain better your statement. By the way I was the senior metallurgist in one of the major independent test labs in the south for 34 years, so we speak the same language.

So in your expert opinion is a visual inspection all that is needed to reject a fastener? I have been a technician for over 30 years and have rebuilt probably 100 engines of all types. I always replace head bolts and main cap bolts on an engine that has been in service for 50 years and is going to be whooped on repeatedly. On regular passenger car engines that have come in to the dealership that need a rebuild due to head gasket failure I always replace the head bolts. What is your professional opinion on reusing plastic region stretch bolts.
I've been doing a lot of rebuilds lately and sometimes the head bolts don't seem to pull that 90 degree turn all the same, some feel like they pull down easier than the others. The bolts are too long to fit my calipers so I have never tried to measure them for comparison.
Thanks
Gus

Obviously if a bolt has stretched or is corroded, bent, or visually damaged, by all means throw it away. If you are not sure, you can measure the hardness, check its structure and grade (destructive tests, in general) and chemistry to see where you are. And as far as fatigue one must know if the stress on it is in the fatigue range, and so is temperature, that has to be high enough to affect the metal. All of these tests make sense in a lab, but practically it's much cheaper and easier to use new fasteners, so I don't have a problem with that.

I look at it this way, there are certain fasteners in an engine that, if they fail, the cost to repair far outweighs the cost to initially replace. Rod and main bolts come to mind. Head bolts don't quite fall into that category for me but the thought of hanging over a fender wrasslin' a head off because the headgasket failed due to a soft headbolt puts those into the replace category for me.

The rest, not so much.

I prefer to use new fasteners in critical applications.


My M120 V12 will likely be getting all new bottom end fasteners after it comes apart for inspection. I do have length specifications for the bolts but would rather spend a few bucks for the peace of mind.

On a related note, it's interesting how far down the single use fastener road Mercedes has gone. All kinds of stuff has single use bolts now. Brake calipers, flywheels, heads, cam caps, main caps, rods, turbos (yellow metal alloy), and many other bits all require fastener replacement.

Yes they see $$$$$$$
Unknown bolts, replace, if you bought new and torqued them right from the start, don't see a plroblem. Like the guy said, they're just springs, how many cycles does a spring have if not over stretched? If you torque a bolt in steps normally one can feel when a bolt-nut is getting weak or not right. My 2cents

Rod bolts and stretch to yield bolts get replaced. Others, it depends on condition and application.
When I rebuilt and changed the gears in my Dana 60, I noticed someone was using mis-matched bolts on the diff bearing caps. I think one may have been a head bolt? I upgraded to studs.
On the ring bolts, I think I cleaned and re-used them with new thread locker on them.

They see lawyers and warranty claims. There are also many aluminum bolts being used to save weight on the cars. Those are definitely single use.






That's a rather uneducated thing to say.

Springs?

Seriously?

Please tell me the modulus of elasticity of various metals.
4130?
4140?
Inconel?
High strength steels?
Titanium?
Aluminum?
Bronze?

Not all metals are the same.

Just repeating what was said. Go jump in his sh!t. Aren't all metal elastic? And when tightened does it stretch? Does it return to its original state after released? I will replace my "bronze" rod and main bolts after each use.

Show me the Inconel bolts on a car. You are trying to confuse the point.
Then show me the titanium bolts on a production vehicle. Or the bronze bolts. Or the aluminum bolts. deliberate obfuscation!

Steel, from the lowest 1015HR to 4340 has a modulus of elasticity of 29 million, plus/minus one million, at 70 degrees F. Aluminum is about 13 million. Gray cast iron is about 20 million and nodular is quite close to steel. It's not rocket science, it IS knowledge that a decently educated mechanical engineer should have in his brain.

AndyF is completely right. The fasteners we call bolts or capscrews are, in most of the uses we care about, used as springs. They exert a clamping force proportional to how much they are stretched, the cross sectional area and the modulus of elasticity. Very rarely do we see a modern fastener loaded in shear.

Another common misunderstanding is the number of cycles a bolt experiences. This will be hard to swallow for some of you. IF the bolt is properly designed and properly torqued (stretched), as long as the bolt does not see a stress greater than the stress from the torqueing, the bolt doesn't see any cycles. For heating, as long as the bolt isn't heated into the stress-relieving band of temperatures, that doesn't have an effect either.

Regarding Mercedes-Benz and the torque to yield bolt, my 1975 M110 engine has torque to yield rod bolts. The factory service manual has a simple procedure to determine if they can be reused. Use a caliper and measure the minimum diameter of the necked down portion. If it is above the specified diameter, the bolt is reused. I admit I was just a little bit uneasy the first time I took my self rebuilt engine and buzzed it to 6500 rpm, but the principle held, as did the rod bolts. The concept of torque to yield bolts is that when they have yielded they are exerting as much clamping force as they can. So no pussyfooting about deciding whether 80 percent of yield or 90 percent of yield is a good value, just torque'em until they stretch. Why do we replace so many now? Maybe on a $35,000 car or a $75,000 pickup the bolts are a minor expenditure.

Regarding throwing away bolts that have not failed in service - I believe it increases your risk. The reason is that the bolt served the purpose well. If they had failed you'd know about it. Now put in new bolts and they are back to being unknown quantities. I guess if they torque up properly they are probably good. But, don't fool yourself that you have lessened the risk. If the FSM says replace them then of course do it. But I have never replaced a main bearing bolt, and very few rod bolts. I have replaced a lot of exhaust manifold bolts and studs due to damage.

So I want to see some aluminum bolts from a passenger car. Maybe Feets knows where they are. I guess I'm still in the iron age.

R.

I'll leave the "uneducated" for others to ponder, but their use is indeed just a "robust spring", with it's strength dependent on design, temper, and material, which to the uneducated, may seem incorrect.

It's time to go meet friends for dinner but if you really want I can send you some pics of the bronze bolts Mercedes uses. Plenty of aluminum bolts too.


As for the rest of your rant, well, rant on.

I know what I know.

You know what you know.

Apparently, the two differ.


Here. I slid a pic in on my way to the car.

Very rarely do we see a modern fastener loaded in shear.

Wouldn't a flywheel,pressure plate,or ring gear be a "loaded in shear" application? Some flywheel bolts have a shoulder built in to keep it from shearing off. Most import pressure plates have pins to help locate the plate and provide additional shear protection from what Toyota engineers have told me.
Gus

.

i used to work on a lot of the olds diesels,they had all kinds of problems but mostly head gaskets from broken head bolts,the gm ones were really hard and were torqued to 130#,ive seen several with the heads popped off,i got to using grade 8 bolts from Caterpillar with a hardened washer under the head,torqued to 125# in 4 steps,never had a problem, with them,once in a while one would stretch when installing but it didn't break just got skinny between the threads and the head

I'm not educated, but IMO the clamping pressure keeps those parts from moving, unless, the bolts loosened up. Like that alignment pin in a camshaft, it won't hold the gear from turning the bolt does by clamping. I was told a six penny nail has a 2000 pound shear capacity. What supprized me is the lift plate that's bolted to an intake that will support a 500 pound engine with four little 5/16 bolts and nuts.

Those bolts will hold like 5000 lbs each !!!!

How many do you want to see? These are in the drawer behind me.

Here's a video I made comparing the strength of thread inserts. I did torque tests as well as pull out tests.

Things go *BANG* when they let go with nearly 10,000 lbs of load.

Did you expect an 8mm (close to 5/16") bolt to hold the full capacity of my Horror Freight 20 ton press?



If you want to skip the intro and go straight to the good stuff...
The torque tests start at 5:20.
The pull out tests start at 13:02.

Ain't that something.

This is better than watching TV.

ob·fus·ca·tion
ˌäbfəˈskāSH(ə)n/
noun
the action of making something obscure, unclear, or unintelligible.
"when confronted with sharp questions they resort to obfuscation"