CAN You Reuse Cylinder Head Bolts? Testing Myths + ARP Custom Aged 625+
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- เผยแพร่เมื่อ 2 ต.ค. 2024
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Today we test various myths about cylinder head studs and torque to yield bolts. Most of which were suggested by you guys, thanks for that!
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Torque, who started TTC, is working in product development for Astro Tools. TTC is not the only testing out there, always consider multiple sources when looking at a tool!
Fun fact: Honda actually says you can reuse cylinder head bolts and gives a separate torque sequence for it (one less 90 deg turn.). This still assumes they're not stretched too far of course and there is a thinness where you replace them.
Do they have a TSB on how to remove the crank bolt?
@@FordRanchero289 Shaped charge using C4.
@@FordRanchero289 no, there's no reason to have a TSB when the proper procedure is already in the FSM. The only difficulty people have is removing the crank pulley bolt without the factory tool to hold the crankshaft.
That tool is available & it works, so there is no failure to justify a TSB. Even without that tool the crank bolts don't give me any trouble, so you must be a pussey.
@@JCWren the shaped charge should contain approx 2500gr C4
Yes as long bolt hasn't been grossly over tightened to the point of necking although the unloaded length of bolt of the used bolt will have increased by tiny fraction the actual load the bolt can carry before failure won't change, also the length of the bolt when loaded to failure doesn't really. What has to checked for is the condition of the threads that they screw in with out binding which would make the initial torquing before angular tightening wrong and make the angular tightening garbage.
Heavy engine tech here. Cummins has a spec for their head bolts for length. A common trick also is to take a nut and thread it up the bolt. If it makes it all the way up the threads by hand on clean threads, the bolt can be reused. If not, then the bolt has been stretched too much and must be replaced. I also replace any bolt that has seen any rust pitting since that creates a stress point that could cause the bolt to fail.
As for torquing head bolts again the next day, the gain you got is within the allowable tolerance, so I would say when torquing, shoot for the higher end of tolerance and even after relaxing, it will still be in spec.
I've never heard of the hammer trick to take the twist out, but I have used that for helping to free up rusty bolts. A couple of sharp raps with a hammer on the end of the stud or bolt helps free up any rust and makes it easier to free the bolt or stud. Not a guarantee, but helps often enough its worth doing every time
Interesting tests and great work. I would love to see a video dedicated to addressing the never ending debate on whether it's ok to use anti-seize and lubricants on bolts because it changes the torque values and clamping force too much- thereby increasing bolt stretch and failure (especially on lug nuts, studs, etc). What is the actual impact on clamping load when we torque to say 100 ft lb dry vs lubricated with anti-seize? Thank you for your efforts.
There's usually a wet and dry torque spec available for that reason.
Never put anything on lug nut dry only
And a t 100ftlbs dry will be less tight that the 100lftlbs lubricated one
Lubrication remove friction and give a better torque reading essential in critical bolt like head stud arp is even more precise with there special lube for torquing
@@legros731 Exactly. Never, ever lubricate wheel studs or lug nuts. They are held in place pretty much only by friction due to their short clamping length. That's the reason why headbolts are so long - the stretch allows them to stay tensioned (it "takes up the slack" during cyclic loading). Short bolts / studs can't take a significant amount of length change without reaching the point of no clamping load, at which point they are free to rotate out.
Also, lubed bolts will fail at a lower torque, so by lubing a dry-specced bolt you're increasing the risk of breaking the bolt.
Anti-Seize isn't exactly a lubricant due to it having an abrasive in it. The lubrication feeling is misleading and generally torque settings are determined on a freshly machined bolt with a light coating of oil left from the machine process. Generally it's a 30% reduction in torque when using anti-seize according to a very in depth study conducted by NASA. That is if you were not provided the Wet and Dry torque specs from the manufacturer. Torque wrenches are an estimation anyway you look at it too. You in no way can measure the linear stretch of a bolt through numbers of rotations. You could measure a bolt length at factory torque, anti-seize it and then tighten the bolt until the length is achieved and that will get you your anti-seize torque setting too.
If you properly stretch the bolt it should not matter what is on the threads as the elasticity of the metal is doing the holding. The massive amount of misunderstandings surrounding this subject has not only muddied the water, it filled it in and black topped over it. Another thing with not using anti-seize on hubs, rims and lugs is the extra torque then applied to the bolts through rust-jacking. There's far more to it once you stop listening to the fear mongering and actually go the full way down the rabbit hole. it took an effort digging through all the "I think therefor it's true" but it was worth putting my mind at ease since what I was being told, sometimes yell told, and what happens in the real world did not match. John Caddogin the Auto Expert .com.au has a couple videos that explain the wheel bolt side of it, worth checking out.
Cat actually has you use copper anti seize on it's head bolt
Another student from the Sloppy Mechanics school of Junkyard LS race motors here. All of my reused TTY head bolts have stood up to boost and abuse across a few builds.
Glad we can get practical experience in the comments too in order to see the whole picture. Thanks
I used an impact on my rod and head bolts on a 4.8 spinning to the moon. So far so good lol
That's a perfectly calibrated reply... lol @@TorqueTestChannel
You need to test the affect of different lubricants on head studs. People think you can use any lube you want, but the wrong lube can lead to over torquing the nuts. Would be great to see ARP lube, vs Detroit Diesel #2 (peanut butter), vs 30w motor oil, and whatever else people use.
The engineers developed the torqueing procedure to be completed as described, not with any other wacky methods to increase the amount of twist achieved. If you get an extra 10-20 degrees by using one of these hacks, you could just be over-yielding the bolts and putting them outside of their strongest region on the stress-strain curve (into the necking region). Either swap out to studs, or use new TTY bolts and follow the procedure outlined by the manufacturer.
Exactly! Everyone always has some stupid hack because they don't even understand what they are trying to achieve. Obviously instead or requiring a waiting period, hammer strikes, ect they would just increase the torque ft/lbs or degrees if they wanted more.
Piano wire is pre-stretched beyond the yield point to increase the elastic limit. After stretching the unloaded length of the wire slightly permanently increases but the maximum tensile load the wire can carry doesn't change.
The reason for pre-stretching the wire is to increase the elastic range of the material and make its behaviour more predictable.
Because of its special properties pano wire was used by Armstrong of England to wind round the barrels of battleship guns to strengthen them and it was also used to reinforce the boilers of Stanley steamers.
This is why I scroll through comments.
The process of drawing wire from larger diameter material down to its final diameter actually increases its strength because of the property called "work hardening". Work hardening actually uses up some of the ductility of the material to get to its stronger state, closer to its fracture point. At about 8:00 in the video is a graph of a stress strain curve. The curve is different for each steel alloy, some steels have a longer and flatter plateau at the top, and the final part of the curve to the right increases again before it reaches fracture. This is the point of work hardening. If you manipulate piano wire until you get it into this final part of the curve where the strength increases again then it will be at its maximum strength, but correspondingly closer to the fracture point.
Interesting. If it weren't for this method, pianos would have to be tuned much more frequently I would imagine.
My personal cannon for quelling noisy late-night parties around the ‘hood failed prematurely…must get some piano wire to deal with repeat offenders!
@@bradbeck2601 and on the opposite end, our old piano couldn't be tuned anymore because the wires were at their breaking point from being stretched and stretched, they'd have to be replaced to get it perfectly in tune again.
Thanks for the work you put in to do these tests. Always entertaining to hear the arguments around the shop afterwards 🤣
I have no clue about any of this but that was interesting as hell. So thanks
Refinery Inspector here- We would never use TTY on any bolted flanged connection. I have discussed TTY with multuple senior mechanical engineers in the same room and here's some thoughts:
TTY is not used because of the amount of variables that are needed, contrary to the original thought of eliminating variables. The first initial TTY sequence is to torque to a low lbs then start the dial gauge.
Problems arise with getting the first torque value correct. A small amount of thread damage, cleanliness, or calibration is off, it's exacerbated at the end and make the torque wildly off.
In addition there is no ability to check final fit up.
Finally, we have great success with hot torque of problem high pressure connections. Torque, run at operating temp for 12 hours, torque with the same values while hot.
Love the video
Just curious - When you "torque with the same values while hot", does the fastener move at all? Or, does the clamping force improve? Just thinking 'what if I could heat a motor up (somehow) and then torque the heads'...would that give me an advantage....mmm
Well the 'myth' on reusing TTY bolts.....I work for a major auto manufacturer (won't mention who to not freek anyone out) and one of our engine types started requiring cylinder head replacements for coolant and oil leaks from the casting. These use TTY bolts that are in very short supply and frequently go back ordered so we are required to reuse these bolts by the manufacturer if they are under a stated length when measured with a micrometer. Note if these are over the stated length they must be replaced. I'm not an engineer just a technician. As you can imagine most techs, me included, absolutely hate this idea but the engineers have obviously tested them as warranty concerns are a factor. We have yet to encounter a problem with any of these cylinder head replacements some being done over 2 years ago. I'm guessing that the engineers see this maximum stretch for reuse as still enough of a safety margin.
Ford ecoboost?
A few manufacturers mention the same procedure for reusing tty head bolts in the FSM.
Subaru impreza doesent mention to use new head bolts even though they are tty as it has 2 90degrees at the end
@@Low760 you beat me to it. Lol
@@Low760 either that or GM 5.3 with the lifter issue.
I work on large AG and have rebuilt quite a few Diesel engines. I mainly work on John Deere equipment. I’ve seen anywhere from measure and reuse (I never reuse) torque to yield that has you let the bolts “rest” for 15 minutes after the initial torque. These are very interesting. I’ve noticed while performing the torque sequence, the first bolt in the sequence is way low compared to what it was initially torqued to. I built a Yanmar once and it said to torque bolts after 50 hours of operation. One thing that was consistent with all of them is coating threads and under the bolt head with SAE 30 weight oil. Something about the straight 30 weight oil that helps keep the torque consistent vs a multi weight. Btw finding a straight weight oil can be challenging.
SAE-30 , take a look in the lawnmower section.
oh baloney, how can 30 vs 10W30 make any difference in torquing a bolt. LOL, everybody knows that castor oil works best
TTY bolts.
When these were first being used, some manuals said that it was OK to reuse for one time however, being number of uses can't always be verified, they recommended replacement. ( I'd have to dig a bit for what make / model ) I think there is actually a diameter / length spec for reuse in some applications. TTY bolts are cheap, the cost to evaluate used bolts can be expensive / skill based so I'm betting that is the driver for bolt replacement rather than reuse.
When installing new TTY bolts you can feel the torque level off before you reach the recommended TQ angle. This extra angle after the TQ levels off gives you enough of a turn to negate any frictional losses in the initial TQ. I've reused TTY bolts by making sure they are original, using the factory pre TQ then turning until I feel the TQ levels off then about 10 degrees more.
For new TTY bolts I've taken not to be worried about an exact angle if I pay attention to the TQ leveling off and I'm at least somewhere near the factory angle.
Bottom line? If for customer, replace TTY bolts. For your own patch together / late night repairs, reuse can be OK.
Most larger diesel engines use TTY bolts that can be reused 1-5 times. Cummins actually supplies a gauge to measure bolts for re-use. However my opinion on the matter, is head bolts are cheap insurance. I've pulled a few cylinder heads that had a snapped in half head bolt resting in it.
if you have the head off, your bill is already going to be pretty big. You may as well cover your ass and replace them.
In my industry we use 2 a490 3/4" fine pitch bolts with shouldered nuts to attach an assembly to our machine. We have to torque them to 425ft/lbs I can testify for the hammer method. We run them on with a 3/4 milwaukee impact. Then torque the nut, smack the bolt head briskly with a 3lb hammer then retorque.
you guys have the best scientific method, and theory testing that i have ever seen!
Checkout Project Farm, he does a ton of interesting testing too!
@@BLKMGK4 I love project farm!
Oftentimes when I need to make a purchase I will review his videos to see if he's made content about the topic
I work on aot of overhead cam ford engines. Depending on the assembly instructions you come across. Some specify to "pre stretch" the bolts. Primarily the ford instructions, and those that copied it verbatim. Their procedure says to got 30 ft/lbs +90°. Loosen it then start over and do +90 twice. I only follow that method on higher performance engines. Stock engines get no pre stretch, and sometimes I've had to reuse old head bolts in a couple holes when new ones yield too much and don't get tighter on the last 90 degrees. Every engine is still running. Some 8-9 years later.
I don't think this is to " pre stretch " the bolts , It is more to give initial compression to the head gasket, release tension then final torque. From what I recall this was on a non TTY engine. ( Maybe an OHC Renault Alliance? )
@@bobroberts2371 the sequence I'm talking about is directly from tty headbolt sequence for the ford modular engines. But yes. There are okder non tty sequences that are similar for exactly what you said. But new gasket technology eliminates that need. Also making sure the center bolts are at the initial torque before going to the next stage after pulling them all up makes a bug difference
BMW is famous for this on their Rod Bolts.
5NM, 30NM, then +90 Degrees. You then back it off one full turn (totally loose) and do it again. THEN you back it off AGAIN and retorque 5, 30, then 90 degrees for a third and final time and you're done.
I found, buried in the service manual, you must stretch the bolts at least 3 times, and no more than 5 times while assembling the engine, and throw them away if removed after the engine is started and ran.
A lot of Nissan stuff did the same …. I didn’t ever do it . Seemed counterintuitive to me. Never had an issue with any
This is to 'bed in' the friction surfaces. The thread engagement points and the point between the bolt head and washer.
The problem with a lot of the high dollar stud kits is that they're only really useful for about half a percent of all the engines out there. Like anything engine-related there's just a lot of smoke & mirrors & straight up unnecessary precision 99.5% of applications just don't need. Case in point is the Honda guy who lubes the backside of rod & main bearings (the saddle side) then clamps the living piss out of his rod & main caps to smash everything down to spec. Now I'm not saying there's anything wrong with stud kits, quite the opposite, BUT, a whole lot of the time it's just straight up unnecessary unless you're trying to 3,000hp out of a 24v Cummins or other such nonsense. My experience in engine building has taught me that if you're lifting heads in blown applications you really need to upgrade your head bolt count from 4 to 5 or even 6 rather than throwing expensive studs at a 4-bolt block trying to keep the pressure in. Same applies to main caps, if your cranks keep walking you probably should spend the money on a 4 or 6 bolt main block, or invest in a good girdle. That's just my 2 cents on it.. often saves money in the long run by avoiding broken parts
I see it with other hobbies as well, the main thing seems to be buying new things to solve the problem, the person is just installing parts instead of putting in any thought or work to find the most effective fix.
One thing that really struck me was the added stretch of the used TTY bolt, it was more than the thickness of a typical MLS head gasket. Which probably explains why the only time I ever reused TTY head bolts the new head gasket failed shortly after being put back into service. The "good to go test" back then was to lay a straight edge on the threads of the used TTY bolt, if the peaks of the threads all touched then it was good to reuse, apparently not in my case.
Possibly over torqued the bolts.
Re used LS head bolts get torqued to 65 ft lbs. in two stages. Have a stock bottom end 5.3 that has seen north of 30 lbs of boost with reused head gaskets and bolts.
Living up to the user name
If the OG factory specs required 94 lbs. for final torque, that's probably what it takes to get the same clamping force without further yielding the bolt.
Sloppy mechanics community, has been doing that for years. Awesome watching guys like this running bigger boost on stock bottom end and reused head bolts. 👍
This is the standard for how all channels should advertise subscribing. Start with interesting content that continues all the way to the end and doesn't waste the viewer's time. Follow it up with a reminder about how consistent the channel is about posting, and how you can follow that consistency by subscribing.
The waiting 24h and retorquing makes sense at first but then you would think and hope the engineers that design them took that into account when giving the torque specs and as such you are already slightly over torquing the bolts to factor in the stretch and the final numbers are the correct torque figures needed. So waiting 24h and retorquing might just be over torquing the bolts and risking damaging the head gasket or bolts. Be interesting if your chan could contact a few bolt manufactures and see if they can let you talk to their engineers on that matter.
I bolted to the computer when I heard about this test. I was hanging on my a thread util I found out wut was wut. It's true, Torque Test Channel testers are all studs. Just saying. Thanks so much.
7:15 if you use a snap-on digital torque wrench and do a degree torque, it flashes the finishing torque in ft-lbs. At the machine shop i worked at, we would torque heads 4 times. First at the seating torque(like 33ftlb), then the base torque (like 66ftlb), then the TTY 90 degrees, and we would note each torque reading from the torque wrench and go back a 4th time and do the rounded up average in ftlbs for the final torque. Never had any issues doing it this way, but just wanted to mention that you can read final torque after doing a TTY bolt. ❤️
Yep, snap-on torque wrenches are great for making sure all of the bolts you're stretching get to roughly the same torque.
Yup I do something similar. Sometimes one bolt will be 100lb-ft and another will be only 90. I don't mind making those numbers a little closer.
Angle torque idea is to get rid of inconsistent torque method, now you "experts" are messing that up.
I did the same thing on main bolts. I torqued them to 20nm plus 70 degrees. Some ended up at 59nm and some at 65nm so I tightened them up just a little bit more to 63nm 😅
The factory manual for my land cruiser does not say that head bolts are single use, and only gives one torque procedure. It does give a minimum bolt diameter, and says to replace bolts if they won’t achieve the torque value or if they’re too thin
Similar to the instructions for my brother’s 81 MB 300SD, bolts have a minimum diameter, can be reused until they get too small, ie stretch too much.
Most of these tips and tricks about putting engines together have been around as long as the automobile has, and most of them probably aren't needed when you take modern engine design and manufacturing techniques into account.
The repair manual for my car actually has a spec for the bolt overall length to see if they're still good to re-use or if they're stretched too much.
I have re-used TTY bolts, but the second time they do feel different to me, less 'stretchy' if anything, but that's not really a scientific measurement. :)
Pretty close though, huh?
You you and project farm had a baby omg my my mind would explode
i've definitely tapped the heads of bolts as i was finger tightening them to take the nasty little bits out of it and the thread so i can take them out easier later when an operator breaks the heads off.
I reused the factory bolt set on a FEW 90's Civic's and on a 88 Turbo Supra I had. Supra's head lifted a few months after i got it, new factory composite head gasket lasted 7 years and about 100k miles in the Supra running about 320hp to the wheel before i sold it. It was my daily and i wanted to keep the original turbo without over spinning it, vertically no turbo lag above 4200rpm. I did retorque after a week of normal driving, repeated 2 more times to make sure they weren't walking out as the 7M-GTE tends to do to head bolts.
I tapped and died the holes and used factory bolts because there was carbon left over, as engine oil is recommended as thread lube per factory instructions. Increased (from i think) the factory 65ft/lbs to 85 ( ithink) i can't remember quite right
Great video, as always.
My 2¢, some I've believed for years:
Never reuse TTY bolts.
TTY allows for better consistency bolt to bolt across the head. (ARP's lube helps reduce that compared to other lubricants).
Additional stretching of the TTY fastener depends on the thermal differential between block/head and bolt. The heat can expand the heads faster than the thermal expansion of the bolt in a few situations. (Loss of coolant a great example.)
The elastic value will differ on the bolt length - they shouldn't be compared.
Torque is a measure of friction; different lubes matter as well as thread polishing.
Friction variation can be 15%; thread surface and lube dependent.
ARP lube significantly reduces thread polishing.
Use exactly the lube specified by the manufacturer when using their fastener. They determined the torque vs. tension with it.
Differential temperature between bolt and head is irrellevant. The difference is minimal, no more than a few degrees.
However, if the bolt and head are made of different materials (i.e. Aluminium heads), the coeffcient of expansion is significantly different between them, hence the clamping load changes.
I'd say that if it took 94 lbs to torque the TTY bolts originally, that's probably the spec you should use for reuse on a well lubed bolt.
I assume that factory specs have been tested to yield the best results. Waiting a day or hitting it with a hammer just changes the specs. If you want more clamping than factory specs, just torque them down more than specs to begin with.
Mythbusters, Mythbusters! Woooo! This would put my friends to sleep but I can't be more delighted! MORE!!!!!!
I have no idea what these are for, but it makes for great going to sleep material
The stress/strain curve is generally fairly flat after the yield point is reached. So, continually applying the same torque will keep turning the bolt until it breaks. This has nothing to do with “relaxation” of the bolt, but is simply the fundamental material property in the yield range.
100% this. Lots of room for error for the same clamping force
Ive reused tty but only on Toyotas. So far no problem xD.
Toyota’s manual does give a way to measure the bolts to see if they are reusable tho so there is that.
Millions of 2az oil burners out there running with reused head bolts. Replaced pistons in over 100 of them myself. The threads in the blocks will pop long before the bolts ever will
@@urMomAtMyHouseDotOrg yes sir.
Ah, yes, percussive persuasion. Right up there with the mighty smack. (insert obligatory 🔨 time joke here)
Regarding re-using TTY bolts - Rover engine official service manual had an head bolt length tolerance - if the head bolts where within a defined max length they can be re-used.
Apparently this is relatively common practice based on other comments I've read.
The Yielded Bolts section got me 😆🤣😆🤣👍👍
Infrared thermometers on bare metallic surfaces are a big no-no unless you are able to adjust the coefficient of emission. If you don't your reading will usually be much less than the actual temperature. If you don't trust me, put some water on your sample and measure the temperature in the dry area when the water starts boiling.
Thank you for testing these! Do you think the 3rd test is just the head and shank twisting on the surface but not moving the threads?
I know you CAN, because I've done it. The question is: should you?
I regularly reuse TTY bolts on components other than head bolts. I return the bolt to the original position or pick a torque specification based on the diameter of the bolt.
I have reused head bolts a few times and use the same procedure.
Thinking of reusing oil housing TTY bolts on 11 Jetta tdi 2.0L . Going back and forth and second guessing because Volkswagen says to replace. Think I’ll be ok to reuse? If so normal torque plus 1/4 turn?
I have re used tty head bolts on two separate occasions. To my knowledge they have never been an issue. I would say only re use them is you are on an extremely tight budget and don’t have to $50-$100 for new stock bolts
Tty head bolts can be used if within a length range generally supplied by engine manufacturers like Hyundai and their terracan j3 engine.
At approximately 6:40, there is a visible oil dropo on underside of gauge, left on screen. During the lets see if the bolt can be tightened after resting for 24 hours: since the intial tighteming wa a "running" torque, I think the re-tightening ashould also be a "running" torque, due to having to overcome friction to get the bolt moving.
I've seen people use a dial indicator and measure stretch, I watched the mechanic do this on a Detroit V8 in an excavator
I've seen MANY! used TTY head bolts snap off while being reinstalled, they put new ones in the gasket set for a reason.
Retorquing head bolts after a waiting period is to compensate for the head gasket relaxing, not the bolt.
After you rebuild start the engine on a stand get it up to operating temperature for at least 20 minutes, let it cool down overnight to room temperature in retorque to head bolts
On the topic of heating bolts to get more tension. On caterpillar hydraulic hammers for breaking concrete with an excavator, the bolt shanks are exposed and you are meant to tighten them slightly then heat the exposed shank in order to lengthen it then let it cool and it will end up being incredibly tight. Might want to mill a window into the simulated head to get access to the shank and give it a try. I know it's not very representative of a cylinder head but it would be interesting to have some data on it in general
Heating the bolts, then torquing them, is standard procedure on steam turbines.
one tip I was given in high-school shop class was to add another torque step. torque the bolt to 5 ft pds less than the rated, let sit for a day and torque to proper spec. so for a SBC, it was a torque rating of 70, torque it to 65, let sit overnight and torque to the 70
I have rebuilt enough engines that never came back to haunt me, because I stuck to manufacturers recommendations. Dry, quality head gasket with new head bolts and perfectly cleaned mating surfaces, usually planed head. You NEVER reuse headbolts on diesel engines, that's just a simple rule. Gasoline engines of low HP without turbo, who cares. You can tighten those with Elmer's glue...still. I'd never reuse headbolts that you don't know the condition of. Safe $500 bucks, just to spend $5000 on a second teardown with failure...no thx. Like driving a BMW on summer tires through a Canadian Winter.
My Snap-On digital torque wrench will read degrees and torque at the same time. When you let off it'll show degrees then torque, then degrees again Tech-angle.
For the 2014 to 2019 6.2 engines instead of the 22f lb then 70 % and 90% i do lubed bolts and blown out holes 22f lbs 67 flbs then 84 ftbs waiting ten mins between torques in sequence .saves a 100.00 bucks each time on new bolts . i disable the fuel management program and no more lifter failures . sorry im getting off topic .
Would have been interested to see you slightly loosen then retorque on test 3.
I've heard in a pinch you can cut used TTY bolts down a bit, maybe a quarter inch, and make them work, just torque a little extra. This was a farm mechanic, so I trust it when he tells me some shade tree trick.. I just haven't tried it myself.
What the heck?? If they stretched so much that you'd have to shorten them you can't reuse them.
Cut down what? The stretchy bit is from the last engaged thread, up until the heads contact surface. The thread's end that you wanna cut does almost no holding at all unless there is very little thread engagement.
With respect to TTY bolts. mitsubishi specify a TTY bolt can be reused if it has not exceeded a given length limit. As specified in the workshop manual for the engine in question.
No the hammer trick is ,,,a hammer hit,,, not a tap on the bolts , you know dog fire hit the head on the bolt right , seasoned head bolts ,,, not over torquing them are reusable in my world 🌎 I’ve never had a problem, but it’s just a matter of time before I snappe one , lol thanks BigAl California.
Yeeey, I see you read my comment about the dial indicator reading from the bottom (or someone elses comment that was the same ;) ).
Cheers bro, you "owe" me one dial :P
I have reused tty bolts on a Buick 3800 but like the Honda I did not use the original method
instead I just pulled them to 80ftlbs then I took them to 120 ft lbs and it worked out ok
And that’s a hot engine in the Australian summer heat 🤣
Subaru has quite a torque sequence for their head bolts. On a mid 00s EJ25 It's basically, in a pattern: 21.4 ft-lb, 50.9 ft-lb, loosen 180°, loosen 180°, tighten 31 ft-lb, then 80 to 90°, then 40-45°, middle bolts another 40-45°. They make no mention of replacing the head bolts or a limit on reuse. They do specify to replace the head gasket. People reuse Subaru head bolts regularly with no ill effects. Would be fun to see you do some testing on them given all the whinging on the internet about Subaru head gaskets! The failures are generally unrelated to the bolts, as far as most people with knowledge are concerned. They were caused primarily by the gasket material used on naturally aspirated EJ25 engines.
Man I'm glad I don't work on Subies. That's a ridiculously long procedure. If it works I guess it's the correct one, but it'd be tedious if I had to do that on the Ford V8s I work on.
@@9HighFlyer9 Try it someday. They are incredibly easy to work on in most ways. I prefer working on Subaru to any brand. Especially Ford. Funny enough, I have a technician friend who left a Subaru dealer to work for Ford. He was there something like 6-12 months and when Subaru offered his job back with a raise, he was so happy to go back. Simply because working on Fords was so much more complicated. Every brand has their downsides, of course. Keep in mind there are only 6 bolts per head. Would take a few minutes to do the full procedure. :D
Hey! I think it would be cool to see a comparison of different metals that have hydrogen embrittlement vs without. I watch all your videos and i love the fastener stuff too!
I've reused head bolts a few times once on a turbo Chrysler 420a running 10psi and never had an issue.
The "hammer" trick was based on snug bolts, then torqued. The reason for this was that any irregularities in the block that could cause friction were removed/seated in the hole threads.. This actually does work, meaning the bolts were less prone to becoming "loose", but it does nothing to the bolt/stud itself.
I do it for my pool filter clamp. It's plastic on plastic with metal bolts. A couple whacks with a mallet and I can EASILY turn those nuts tighter. I just keep going till it's not easy to do anymore. I imagine it's the same for just about any other high friction application.
They do this to relieve tension in body work. When you push/pull a steel panel back into place, you tap where it joins to relieve the tension in the metal so it doesn't try to return to it's former shape due to steels elastic properties.
It's also used on wooden props with aircraft. Wood props require periodic re-torque because the wood compresses over time (unless you have steel bushings). Giving it a good whack with a mallet and a second re-torque equates to less torque lost before your next re-torque. It's also a way to get that last bit of torque out of a larger radial engine prop nut, when you're hanging with all of your weight on a 4ft extension bar and someone taps the prop shaft, you can feel it tighten up just a tiny bit (600+ft/lbs, you do it by weight and moment arm, not a torque wrench...imagine the cost of 4-6' long torque wrench that needs to be regularly certified and calibrated above 600ft/lbs).
Depends on the engine. On some engines they can be reused many times
How does torquing a stud not put a twist in the stud? Friction is roughly 1/2 in the head, and 1/2 in the threads. A stud or bolt both puts the thread friction torque into the length of it. The advantage is the threads are hard steel on hard steel, not hard steel on aluminum or cast iron, so there remains an advantage. Another comment is how about comparing ARP thread lube to Internatioal Compound #2, aka "peanut butter". I have found that torque a 7/16 rod bolt to get the spec stretch requires around 90 lb-ft of torque, but the torque spec is 70. I can feel the bolt turn as torque rises, up to about 70 lb-ft, then it seems to stick as if the threads are biting through the lube. A 3rd comment is burnishing the threads by torqueing 3x.
Just something ive been curious about. How about testing different methonds of lubing the thread? Like is thread grease best, or maybe engine oil? Especially compared to nothing.
The best lube is the one thy call for most head bolt need engine oil to torque arp include a special lube with number with said special lube and with engine oil
Always wondered this myself too , I use arp lube on most stuff these days but be good to know
Hello dear TTC team
A German car enthusiast made some head bolts because the ARP ones weren't strong enough for him. They supposedly have a tensile strength of 270.000+ psi (1850 N/mm2/). They are called Pro Series Fasteners. Maybe you are interested in testing them.
Arp custom age 625 plus bolt have a tensile strength of 260,000 to 280,000 psi
And the Aermet bolt are rated at 290,000 to 310,000 psi
So no is bolt are not better that arp just better that arp2000 bolt at 220,000psi
All torque wrenches have a tolerance. Slight difference in measurement could be because of that.
The reason for the tty bolts is that during the plasticization phase, it lowers the preload on the threads themselves. This lower preload in a repeated expansion/ contraction application leads to less long-term failure from high loads enableling a smaller fastener size. You can reuse bolts with stretch left because it's all about preload and there are Guages that measure the bolts.
When I was working in a garage many years ago, they used to say to re torque the bolts after 3000 miles. That gives the engine, head and gasket time to settle and then the head bolts and gasket should last the life of the engine. Head gasket failure is usually down torquing the studs in the wrong order. Usually you work from the centre of the head out.
On mercedes engine (tuned) we use 12.9 bolts instead stretch bolts and we do 50nm then loosen 50-70-90nm run engine hot let it cool down completely then 120-125nm seems to work great.
Because not TTY bolt.
Tons of different types of tty bolts. Lots of manufacturers re use them. Honda, Chrysler, so on. Some actually have a special tool that is a thread gauge to test for stretch
I’d really like to see the xotic heads be put up to the test with arp studs
I reused bolts on a Lancer 1.5L, a Renault 5, and a bunch of Volvo 240. No issues. 99% sure my old Civic 1.6Vtec had reused bolts too after a valve change, it too had no issues for the 3 years it was used after that.
Great video. I was excited to see the re-used tty bolt, but everyone says to use a torque of around 65lbft and not to degree it again. In my head that seems like a better method instead of double yeilding the bolt.
One retailer of ARP headstuds for cummins had a specific tq sequence, and it was a pain. You would work your way up to final tq, then loosen and torque again 3 times, plug the block heater in over night, let it cool, then do a final tq. No idea if this extra work helped, but i never puked a gasket that way
TTY by definition has a permanently smaller shank diameter. Reusing it starts off as a smaller shaft with less ability to sustain stress.
Great video guys!
I have found that reusing the same bolts the engine was originally built with has never been a problem. Using a best practices of clean and flat mating surfaces along with proper bolt tightening pattern and stepped torquing has always giving me failure free results. All the failures of engines, gearboxes and structural items has been traced to exceeding load limits. Always use a good quality torque wrench and have it calibrated to maintain accuracy. I avoid using air or electric impact tool for assembly. It's too easy to over or under tighten fasteners with an impact wrench.
You cant always rely on that as tty bolts undergo irreversible plastic deformation every time you yield them.Sure u can probably get away with reusing them few times but you cant reuse this bolt forever, personaly i wouldnt use it more than twice.
On small fasteners I've tried the hammer before the final torque thing. I had no way of measuring the tension but they definitely do turn a little more with the same torque limit on the wrench. This was on rifle scope rings so very small fasteners. I knew a marine core sniper and firearms trainer that did this for fighting rifles.
so, I'm wondering about main cap bolts. For LS they are torque to yield / angle torque spec. How are you supposed to set bearing clearances without ruining the bolts? You need to use the torque sequence to achieve proper clamping for check bearing clearance. So then when re-installing the bolts with the crank etc, is the bolt already ruined / per-weakened?
Torquing does not affect the clearance so you don't have to tighten it till it starts yielding.
A lot of misconceptions about torque vs angle in the comments it seems. Angle is superior in every way when trying to develop a specific amount of clamping pressure or bolt stretch. The torque required to do so can change drastically, depending on lube and many other conditions. Torque is an indirect measurement. Angle will directly tell you the amount because you know the thread pitch and the bolt's material.
Kind wanna see a 6.0 powerstroke OEM bolts vs ARP studs and the ARP 625, then throw in a cheaper version like those Amazon Xotic performance. The long time theory is the factory bolts stretch causing head gasket failure which I’m a little skeptical on for a stock tune
The load loss you are seeing in the heated test, and the relaxed test is due to a differential in thermal expansion. The increase in bolt load is, in fact, causing an increase in embedment, gasket creep, and, most importantly, gasket stress (gasket crush). The gaskets do not recover well, so you will lose gasket stress and bolt stress when everything reaches soak temperature and then cools.
Huh. I guess Nissan agrees with you on reusing TTY bolts. They don't provide them when 5.6L short blocks are replaced.
Have you considered testing how 12.9 socket head cap screws work as head bolts?
When I torque a head, I lube the threads and under the head, except SB Chev which gets sealer on the threads, then I go through the pattern and steps counting each bolt so I know I didn't miss any. I then go back through the pattern loosening each bolt slightly, maybe 1\8 turn, and then pull it to torque again. Lastly, I start at one end and check each bolt to see that it is holding torque; I have had a few blocks where soft threads showed up during the last step, requiring Heli-Coils. If it is a TTY, I then pull the proper angle. This is how I was taught in my apprenticeship and I have never had a head gasket or bolt failure.
Before the days of PermaTorque head gaskets, we would go through the run-in procedure to break in the cam, about 20 minutes, and then retorque the heads.
I have never reused TTY bolts since stock replacements usually come in the kit or are cheaper than the repair if a bolt fails, which I have seen happen.
as i work on boilers the temp is a thing. i have to torque to about 125 ftbl to hit my flextalic gasket numbers. so 400 degrees at 300 psig.
Some Mercedes have reusable head bolts if it measures within a certain length.
When you did the heat test, I wonder if the increase in torque might have been in part do to the hydraulic oil expanding from the heat as well
I thought of that too but it would have to heat the whole reservoir as well to make any appreciable difference. Just looked it up and oil expands by about 4% every 100*F. Aluminum is about 1/4 of that and iron is about half again as much, so it would be significant if it was warming up that much. He could check the temp. of the output fitting on the pump he's using. My guess is that not much of that heat is getting down through the column of oil though.
It would be very interesting to see how socket head cap screws compare as well as xotic brand.
I was hoping to see a comparison between roughing up the arp washer on the “engine side” vs not. Steve Brule wrote an article that I mentioned on your original video.
ARP sells washers with dimples as well. Also depends on the surface finish under the washer, that metal he used didn't look too polished.
Great Video. I really appreciate the scientific testing and results. Nice to have unbiased information. Thanks
Only 27 thousands of a stretch that is impressive
For re-using TTY bolts, I think you should measure the final torque for the new bolts + 90 degree and torque the used bolts to that with grease. That should get you as close to the original spec as possible with re-used TTY bolts.
Torque vs. tension- if tension is the goal then torque is a poor indicator of what tension you have. There are too many ways that torque can be affected before it gets to the point of elongating the bolt. As for the measurements of elongation vs. tension- these should be consistent with normal elongation calculations using youngs modulus. Youngs modulus should be almost identical for all of these fasteners although slight changes in metallurgy can affect it a small bit. If you are seeing big differences then there might be differences in bolt shank diameter, things like that. You should be able to get the elongation measurements to agree exactly with the tension in the bolts. When you tested one of the bolts and commented that TTY bolts elongated more than that during their torque process- yes that's the idea behind TTY bolts. You torque them so they pass the tension yield strength of the material so they will naturally elongate more than a fastener that is not installed to its yield point.
As for torque to yield bolts- you showed a stress strain curve. When a bolt is torqued to yield it has traveled up the steep part of the curve and onto the flatter part at the top. This provides a bolt that has its maximum elastic clamping ability and if you provide enough turn of the fastener to get to this point then you have removed torque and friction and all of those variables from the process. If you remove this fastener, its elongation doesn't travel back down the stress strain curve the way it went up, it instead plots a new line straight down to 0 stress following the steepest part of the initial stress strain curve and gains a net strain when it hits zero stress. Now retorque that bolt and it travels back up that second line onto the plateau and farther along the plateau towards the point of fracture. You are using up more of the small amount of ductility that the fastener has and pushing it closer to its fracture point. It should still have the same strength and the same clamping force, but would be closer to ultimate failure, the fracture point on the stress strain diagram.
As for thread lube- go back up to the first part of this comment. Without thread lube a lot more torque goes into overcoming friction and not achieving elongation and clamping of the fastener. Ideally you would use lube on every fastener that is required to be torqued. If you disassemble an engine to work on it, when you get ready to reassemble look at all of the fasteners that were removed and look at the condition of the threads on each one. You will probably see a variety of conditions- dry, rusted, oily, dirty, etc. Each of these will torque differently. I've watched tests of tightening structural bolts for buildings using a Skidmore-Wilhelm machine and the clamping force varies widely depending on the thread condition, thread condition probably being the most significant variable in bolt tightening.
As for your test of temperature- if the entire engine is at operating temperature then the head, the block, and the bolts will be at the same temperature, they will all expand the same amount, and the bolt tension should not be affected. If you heat the block with a torch the bolt will not be heated, the block will expand, the bolt will not, and the bolt will be pushed against by the expanded head which will increase its tension.
Fastener design guy here, everything you've said here is accurate. You did it a very good job explaining relatively complex concepts in such few words bravo.
I wish I had the ability to publish data from my tensile frame, it would describe what they're trying to do here with this cobbled together set up in a format so much easier for the layman at home to understand.
This may be a picky point, but some engines have aluminum heads. Aluminum has a different coefficient of thermal expansion than the steel head bolts. In these cases, the bolt tension will be affected by the engine being heated to operating temperature. I am rebuilding a Volvo B5254T2. The TTY head bolts are not accessible once the cams are installed, and are to be replaced according to the manufacturer.
The hammer thing might help if there is a bit of grit in there that you gotta knock free.
ill tell you that putting the socket on and tapping the nut/bolt while breaking them loose DOES help
its NOT for torque / install...... but for removing
.
at the very least it removes that "CRACK" and then vibration you get in your hands that hurts
Underground torque spec :65-70 ftlbs. Not recommended. But I know people that ball on a budget and have had luck
My ac delco digital + angle torque wrench will tell you torque applied when you torque via angle. Most ls head bolts end up between 75-110ft/lbs after the final pass. It's a pretty ridiculous range.
Ph.D here MechE. Look up joint relaxation. Fastening engineers treat a fastening solution as a system, not the bolt by itself, and determine an appropriate success metric. The bolt by itself is just a component.