CAN You Reuse Cylinder Head Bolts? Testing Myths + ARP Custom Aged 625+

[@nmbmtl]

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.

[@FordRanchero289]

Do they have a TSB on how to remove the crank bolt?

[@JCWren]

@@FordRanchero289 Shaped charge using C4.

[@Iowa599]

@@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.

[@appelmelk5664]

@@JCWren the shaped charge should contain approx 2500gr C4

[@andrewwmacfadyen6958]

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.

[@bobbygetsbanned6049]

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.

[@dangerrangerlstc]

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

[@MattPratt]

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.

[@TorqueTestChannel]

Glad we can get practical experience in the comments too in order to see the whole picture. Thanks

[@alexs.5675]

I used an impact on my rod and head bolts on a 4.8 spinning to the moon. So far so good lol

[@tjoyce81]

That's a perfectly calibrated reply... lol @@TorqueTestChannel

[@4b131]

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.

[@Low760]

Ford ecoboost?

[@bleach_drink_me]

A few manufacturers mention the same procedure for reusing tty head bolts in the FSM.

[@kirilakmadjov8307]

Subaru impreza doesent mention to use new head bolts even though they are tty as it has 2 90degrees at the end

[@mattmckie6967]

@@Low760 you beat me to it. Lol

[@JamsheedRpgGodBoss]

@@Low760 either that or GM 5.3 with the lifter issue.

[@andrewwmacfadyen6958]

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.

[@c0c0asauce]

This is why I scroll through comments.

[@billj5645]

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.

[@bradbeck2601]

Interesting. If it weren't for this method, pianos would have to be tuned much more frequently I would imagine.

[@wallacegrommet9343]

My personal cannon for quelling noisy late-night parties around the ‘hood failed prematurely…must get some piano wire to deal with repeat offenders!

[@AlexanderBurgers]

@@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.

[@afellowinnewengland6142]

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.

[@smnkm4ehfer]

There's usually a wet and dry torque spec available for that reason.

[@legros731]

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

[@kain0m]

@@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.

[@demuskumarius]

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.

[@TheCntryson47]

Cat actually has you use copper anti seize on it's head bolt

[@AaronBlankenship]

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.

[@PoorSharkie]

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. ❤️

[@richardzielinski5707]

Yep, snap-on torque wrenches are great for making sure all of the bolts you're stretching get to roughly the same torque.

[@aaronpops4108]

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.

[@V8Lenny]

Angle torque idea is to get rid of inconsistent torque method, now you "experts" are messing that up.

[@dominikkozela9763]

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 😅

[@yourolddad6407]

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.

[@SinsBird]

Possibly over torqued the bolts.

[@Drmcclung]

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

[@lolatmyage]

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.

[@Busted_Knuckles]

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

[@tjoyce81]

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

[@AutoRepairTips]

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.

[@TorqueTestChannel]

Living up to the user name

[@fascistpedant758]

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.

[@Bsk0123]

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. 👍

[@harleyhaynes]

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.

[@bobroberts2371]

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.

[@gszman]

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.

[@unbiasedcobra6672]

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.

[@MikkoRantalainen]

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.

[@cerneysmallengines]

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

[@AlexanderBurgers]

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. :)

[@kennethdandurand3472]

Pretty close though, huh?

[@willagresham2978]

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.

[@jafa1402]

SAE-30 , take a look in the lawnmower section.

[@FourthWayRanch]

oh baloney, how can 30 vs 10W30 make any difference in torquing a bolt. LOL, everybody knows that castor oil works best

[@bigc9464]

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.

[@bobroberts2371]

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? )

[@bigc9464]

@@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

[@monte0704]

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.

[@scottallpress3818]

A lot of Nissan stuff did the same …. I didn’t ever do it . Seemed counterintuitive to me. Never had an issue with any

[@andrewdynes5300]

This is to 'bed in' the friction surfaces. The thread engagement points and the point between the bolt head and washer.

[@paulwolf8444]

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.

[@blkmoon33]

Thanks for the work you put in to do these tests. Always entertaining to hear the arguments around the shop afterwards 🤣

[@frijoli9579]

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.

[@ittimjones]

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.

[@Cheepchipsable]

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.

[@Skinflaps_Meatslapper]

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).

[@tonysheerness2427]

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.

[@jrt2924]

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.

[@oluskloc]

Because not TTY bolt.

[@deankruse8751]

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

[@dickmick5517]

Heating the bolts, then torquing them, is standard procedure on steam turbines.

[@lelandlewis7207]

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.

[@pflaffik]

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.

[@magmomwise]

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.

[@kirilakmadjov8307]

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.

[@stevegarboden2437]

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.

[@siliconvalleyengineer5875]

Sine 1910 the auto induatry installed head & crank bolts dry with no thread lube or lock-tight of any kind, those engine would last 100 to 200 thousand miles. torque to yield bolts are garage, I will never install them in my pre 1980 big & small blocks. If your planning on installing standard head bolts always use grade 10.

[@Joeameturexpert]

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.

[@tombowman100]

Here is another tip I learned from a legend Nascar engine man. After initial engine runs have been accomplished and cool down in the same installation sequence Loosen first bolt 1/4 turn Apply final installed torque Repeat this process in sequence

[@kswis]

I hope this doesn't cause folks to reuse yielded headstuds. There will be many more broken down cars on the side of the road. They did better than I imagined but still, they're already stretched dead. Excellent video

[@MurphyTheBandChild]

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.

[@pike7318]

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.

[@legros731]

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

[@802Garage]

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.

[@9HighFlyer9]

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.

[@802Garage]

@@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

[@toomanytoys]

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.

[@kain0m]

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.

[@randr10]

I very specifically remember seeing in old repair manuals (like 1960s or older) that if you're going to install a head, you torque the bolts, heat cycle the engine once or twice, then re-torque. I did this most recently on a Kubota diesel engine and I did in fact get a significant increased turn on several of the bolts at the same ft-lbs on the torque wrench. I'd say like an 1/8 turn or so, maybe a little more on one. I figured since I needed to go in the valve cover and check the valve lash after a short run in as per the factory repair manual, I might as well torque the head bolts again. I was surprised that so many moved honestly because it was a modern head gasket and the factory manual didn't say anything about doing that. Kind of glad I did now.

[@randr10]

I also think it would be interesting to do the TTY bolts with a series of goldilocks-finding torque attempts. Like you could go 60-65-70-75 and then test them all for stretch under hydraulic pressure and their failure point. The scientist in me is convinced that there should be a sweet spot to get another use out of them. Just thought of something. Use a beam style torque wrench and torque on the bolt until it gets to the same pressure range as the original TTY sequence, then record the number you reach. Maybe do 3 or 5 to see if they're consistent, then do your stretch test to see if they're weaker after re-torqueing.

[@timw.5030]

I have no clue about any of this but that was interesting as hell. So thanks

[@mareprah]

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

[@MrHeHim]

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

[@nickmcwilliams685]

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.

[@MegaMarclar]

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

[@Kanglar]

I know you CAN, because I've done it. The question is: should you?

[@MrElbowgrease]

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?

[@SinsBird]

Torquing does not affect the clearance so you don't have to tighten it till it starts yielding.

[@matd3150]

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

[@fascistpedant758]

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.

[@fitzmorrispr]

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.

[@MF175mp]

Depends on the engine. On some engines they can be reused many times

[@bigwangmark]

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.

[@boblewis5558]

Answer: yes of course you can. My first car was a MKI Mini and I had the head off it no end of times ... Replaced the head gasket (because that was usually the reason for removing the head ... Classic mini problem. In the end Hermetite orange silicon gasket sealer PLUS a new gasket solved the problem. But I NEVER needed to replace the studs which always torqued up just fine thanks! In principle if not in practice, torquing the nuts properly should not cause stud deformation, only minor, elastic, non permanent stretching.

[@seancollins9745]

the problem is that once you get past the point of stock or ARP replacement headbolts, the head starts to bow between the cylinders and unsettle the gasket, with stock type cylinder heads. At that few after market heads are significantly strong, shy of a billet of HIP cast head, I doubt much more than a standard stud is all anyone will ever need. Thanks for the testing however. If you doubt this, grab a head and block and use impression paper.

[@jdrok5026]

There is a lot of variables for that.

[@bobc8694]

I am a 3 generation mechanic and have built so many different types of engines over the years I couldn't even begin to count them.. but I do a lot of SXS engines mostly Polaris RZR and there snowmobiles as well. And with the amount of race engines I build with all the best parts.. I modify and build even more engines for the every day trail rider.. And I'm always looking for the best parts that are going to last the longest if it's maintained correctly. So with that said I have been testing the one time use only hard wear for a long time mostly on Polaris and some car stuff. And on Polaris I have found that a good amount of time you can reuse head bolts and some others. But it's time consuming to do so. Mostly checking them out.But I have come up with a process of checking the bolt and if it checks out good by my specks then I have a torque process for the bolts that has been back up since 2008 to 2016 by 30 engines that was part of the R&D from 2016 until now I have 90ish engines out there running around and 15ish of them with over 5 thousand miles on them.And my personal Polaris 08 RZR 800 that I bought with a bad engine with only 1500 hundred miles on it and that was the start of the R&D I sold that machine to a good customer of ours with about 15-16 thousand miles on it and at the beginning of this summer I was talking to him and he has over..30.. Thousand miles on it !!! Pretty crazy but he's retired and uses it all the time and he takes care of it just like I showed him how to do and what time frame to do different things to the machine ,air filter, oil and filter, just to name a few.. l am sorry this is so long and it doesn't have all the periods lol but I think most people will understand what I'm saying and I thought people would like to know if you take your time and think about it you can figure it out this post just let's you know that most of the bigger bolts will work just fine just don't torque to the degree part since it is now a normal pre stretched bolt TQ only have a great day... Bob...

[@DrHarryT]

I did an 05 Duramax with new TTY... Did the primary torque sequence and then the two 90 deg stages. One thing I noticed was that a few of the bolts went to the final 90 deg turn with less resistance than most of the other bolts. My brother was doing the final [I am an ASE certified veteran] 90 deg and wanted to go past the rotational point and I abruptly stopped him... NO! I suspect in those bolt holes there was some residual oil making them easier to turn. I told him that threads work, every bit you turn the bolt stretches the bolt more and more. Stop at the specified point and you have stretched the bolt to its spec. Leave it alone, it's got the proper clamping force and it's not going to magically unthread. So much for skimping out on the brake clean. He has a 1,000 miles on it now with no problems... So far.

[@immikeurnot]

IIRC, GM had a 4 cylinder engine that you had to run to temperature before finishing the torque sequence. But yeah, it's smarter just to do it the way the engineers told you to. They may be screwups on a lot of things, but not usually head bolt torque.

[@matthewzuber9823]

you guys have the best scientific method, and theory testing that i have ever seen!

[@BLKMGK4]

Checkout Project Farm, he does a ton of interesting testing too!

[@matthewzuber9823]

@@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

[@mathuetax]

Mythbusters, Mythbusters! Woooo! This would put my friends to sleep but I can't be more delighted! MORE!!!!!!

[@chrissraceporting7055]

Tty head bolts can be used if within a length range generally supplied by engine manufacturers like Hyundai and their terracan j3 engine.

[@GlyphZero]

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.

[@derekhobbs1102]

Got to love having an old Datsun L series with 40+ year old head bolts. Mainly because new bolts weren't viable when mine was built.

[@robertlindsay9826]

I had mayby 10 when I was younger. So simple and economical. I miss those simple days

[@billl7551]

Either a heat cycle or waiting 24hrs is for the torque relaxation due to head gasket compression, not metal creep, yielding of the fastener. I like your channel as many of the tests are very good, some could be improved. Stretch is strain in engineering terms and is based on the modulus of the material for the stress-strain relationship. Just stretch is not very meaningful as a comparison of different fasteners, but it is interesting. Permanent deformation (stretch) would be comparative if it was only based on the reduced diameter section.

[@savagerb28]

The torque spec commonly used for a re used LS head bolt is 68ft pounds! We’ve made over 30 psi of boost using this method.

[@brarautorepairs]

Are the bolts installed wet or dry?

[@kiyosenl.3889]

You can use one of those digital torque guage adapters to read the torque being produced while you do the angle

[@BrokenBimmer]

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!

[@christophershafer5615]

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?

[@ovalwingnut]

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.

[@jamesuzzle3143]

65ft lbs is what we have always torqued sbc and ls heads to. Whether it was reusing factory head bolts or arp studs

[@GarageSupra]

I Just started watching the video however, I have used lubricated ARP 2000 head studs in my 2JZGTE and didn't retorque after heat about 7 years ago and have had no issues with the MLS and single turbo upgrade. I think ARP takes this into account with their torque ratings for the 2000 series bolts. I would say the alloy in the head would be more of the stretch point if anything

[@frosty9595]

The video shows that retorquing isnt an issue.....

[@matrix860321]

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.

[@TCFiveoh]

I re-used a TTY set of head bolts on a Ford 4.0 OHV. The only thing I did different was add 5 lb-ft on top of the factory spec 3 stage sequence to get the bolt to yield a little more on the stress vs. strain graph. This was at 120k miles and at 185k miles there was still no issue with that truck. IMO, It would have been a better comparison to do something similar to get the bolt to a "new" yield position further along the Sy hump. I feel torqueing it to the same spec as an un-used TTY bolt wouldn't guarantee the same load generated/tension in the fastener.

[@TKC_]

Structures (think bridges) use yielded bolts in what they call slip critical connections and the aisc has published a significant amount of data about bolt relaxation and torquing procedures based on many years of research. The procedure used for turning beyond into yield by measuring degrees would go by the name of turn of nut method of tension control and is very common. They have done many tests about bolt relaxation and your results are very close. The relaxation happens on an exponential decay with the majority of it happening within the first hour or so after torquing. if let’s say 100 bolts are in a joint 10 would be rechecked later and if found to be low on torque corrective action would be needed. They do permit the reuse of bolts with engineers approval if a nut can thread on (these bolts yield the threaded area, not a separate shank area) however I’ve never seen an engineer permit it. Torque wrenches can be used instead of turn of nut methods after calibrating to torque tension relationship on what is essentially a fancy hydraulic cylinder called a skidmore device.

[@hotironforge1385]

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

[@sypher0101]

Q: If you install TTY bolts, then later on you need to take them off for whatever reason & decide to re-use them, do you still need to do steps 1-3 (below) or are those steps to pre-stretch only & as they've been used, no stretch is needed? 1.Tighten all bolts to 29.4 N·m (3.0 kg-m, 22 ft-lb). 2. Tighten all bolts to 58.8 N·m (6.0 kg-m, 43 ft-lb). 3. Completely loosen to 0 N·m (0 kg-m, 0 ft-lb). 4. Tighten all bolts to 27.4 - 31.4 N·m (2.8 to 3.2 kg-m, 21 to 23 ftlb). 5. Turn all bolts 50 to 55 degrees (target: 50 degrees) clockwise

[@thomasallbee52]

Some manufacturers tell you tty bolts can be used again if the threaded section hasn't deformed. This can checked by measuring dia. of threads across the middle and ends of threads, or a straight edge, thread pitch gauge or even a nut will thread on differently in a streached section getting sloppy or difficult to turn.

[@madmatt2024]

Yep. Chrysler says just this in the service manual for their 3.6L V6.

[@hydrocarbon82]

One thing I noticed with re-used LS bolts (head, rods, mains) is you can't use the tq+angle method. It leads to a very different clamping force. I had marked bolts in an untouched factory block, loosened, then torqued - they ended up going past the marks each time and different bearing clearance. That seems in-line with what Honda says about re-using their bolts.

[@thevictim2072]

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.

[@hardcore4476]

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?

[@alro2434]

Hammering it just compresses the gasket which doesn't spring back, also shrinks slightly what ever else is being clamped. Beside seating it by beating down the high spots where the mating surfaces contact each other! ALSO, TTY is a specific fastener made to stretch, once, one time , while way to many think that every fastener that uses an initial torque value plus an angle or 2 is a TTY! It is not & those are very reusable, only those with a narrowed/necked down area/s is a TTY, and is reusable only with great caution.

[@borisp9499]

Here is how to re-use a TTY bolt and get the same tension. Get a new bolt and tighten it to spec. Then mark the bolt head position. Then remove the bolt and tighten it back to the same position that you marked. Forget about angle or torque, just get it back to the same head position. Then you will have the same clamping for as on the first tightening. This is why TTY bolts have to be discarded, because nobody is going to go through the trouble of marking the position of the bolt and then re-tightening it back to the same position.

[@LTVoyager]

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.

[@TorqueTestChannel]

100% this. Lots of room for error for the same clamping force

[@douglasmayherjr.5733]

Great Video. I really appreciate the scientific testing and results. Nice to have unbiased information. Thanks

[@alarson1981]

On the re used tty bolts the seasoning matters- you want bolts that have been torqued and heat cycled for like 10 years and 150k +. It is also best to torque them to a number not to yeild like new bolts. 70 ftlbs is the number LS guys use.

[@willtricks9432]

Short answer, yes. Long answer yes I have on my 3.5 V8 four years ago and my Landover pulls a ton of logs all year round on and off road with no issues.

[@bluntmuffin1729]

Hey I made some of those bolts! Really interesting to see these tests.

[@TorqueTestChannel]

Well done!

[@ReefMimic]

You you and project farm had a baby omg my my mind would explode

[@twicebittenthasme5545]

I always had wondered about that myth of hitting the bolts with a hammer. I recall many instances of having to to wait final assembly for the "tapping" of the head bolts with a hammer by the old mechanics when I was an apprentice so many eons ago. The very same reasons as noted were given for this procedure along with "seating" the bolt head as machining from other shops shouldn't ever be taken at face value. Always seemed to be an unnecessary step as I never saw or heard of any failures whether hit or not.

[@yogibarista2818]

Glad to see you've stopped trashing dial gauges - that was really hard to watch before.

[@cueball108901821]

I worked on helicopters for 10 years and the “hit it with a hammer method” is actually an installation procedure that is used. We used it to install generators on the main gear box. The generators are held on by a beefy band clamp style mount. After you torque it, you hit around the entire clamp and re-torque. This process is repeated until the bolt does not move two consecutive times. Typically we’d get about a quarter turn more on the bolt before it stopped moving. Now, this was low torque, only 60 inch pounds. I’m curious if high torque negates the need for all that.

[@JoeSmith-lp8fl]

Might have something to do with differences in application.. A band, even a beefy one, is quite different from a cylinder head with lots of bolts or studs being tightened in sequence that should create any movement needed for solid torque. Hammer blows would be unlikely to shock and move the materials due to quantity and torque. (My opinion)

[@jdrok5026]

Well since most auto stuff is located by a mixture of bolts and Dowels you shouldn't need to hit anything. Infact its a dumb idea as you run risk of damages to threads the bolt head even the heads themselves. They are designed to actually be hit.

[@nono-fn3zc]

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.

[@BOOT]

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.

[@charlesenfield2192]

My theory of myth 4 is that it may help if you do sloppy work. Fouled or dirty threads, insufficient lube, etc.. If tapping a bolt with hammer helped when work is done properly, it would be included in the instructions. I'm not suggesting that all instructions are perfect or optimal, but in this case reputable part manufacturers and OEMs have researched the heck out of this for decades. It's unlikely that any individual mechanic has better data than they do.

[@WildDisaster]

The problem now is that reputable part manufacturers are less in number than before. So these methods come into play more these days as a distrust of quality control has developed.

[@jormungandr9840]

I am a Ford tech and when torqueing down the crank pulley bolt on the 1.6l Ecoboost before the final torque it actually says to wait two seconds before final torque. I always thought that was odd because it takes more than two seconds to adjust for the final torqueing. But maybe it has to do with relaxing the bolt but it's just two seconds. I know it's not cylinder head bolts but it's a TTY.

[@Deneteus]

There is a way to heat that block to engine temp for testing that doesn't require a blowtorch. Just use cartridge heaters and a PT1000 RTD sensor with an ESP32 board. That would give you temp and time data for long term testing if you wanted.

[@me3333]

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

[@randr10]

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.

[@TC-V8]

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.

[@ddegn]

Apparently this is relatively common practice based on other comments I've read.

[@jpop2499]

It would be very interesting to see how socket head cap screws compare as well as xotic brand.

[@cch201992]

The term for the hitting it with a hammer thing is called penning it's used to relieve the stresses mostly used in welding at a joint where the material can shrink when it cools

[@TorqueTestChannel]

That'd be peening

[@cch201992]

@@TorqueTestChannel ah yeah that's how it's spelled haha would be interesting to see you hit the bolt with a needle gun because that's something we would use it has alot more vibration 🤷🏼‍♂️

[@alkennedy1124]

The static seep down sigment is a leaky hydro cylinder, if you look at the bottom of the plug/ fittings there is fluid dripping 💧off the bottom of it , so those reading are 100% wrong in that sigment , lol nice thanks BigAl California.

[@jsteganius6969]

Did many head gaskets on cars that the headgaskets were old and chewed away. Reused the bolts and away they went with absolutely no problems. Found out years later the head bolts were supposed to be replaced. Same old b.s. Saw a buddy of mine put head gaskets on a Subaru and had to immediately take 1 head off to replace 1 new head bolt that just broke off while tightening. Replaced it with an original head bolt and away it went.

[@franktechmaniac7488]

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.

[@leehulbert927]

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.