Head stud stretch

[powerfulone]

This issue has arisen a few times over the years. I've used aftermarket head studs and nuts over the years on Busa's. I have noticed that the nuts are never as tight on a strip down as when first installed. Some rebuilds have been because of head gasket failure. Head studs have to have elasticity in them to cater for the expansion of the aluminium engine when hot. If the studs elasticity is insignificant then its going to pull the case threads and the head torque is going to back off. This may not be a problem with drag motors as they do not get as hot as circuit or top speed use. I have just had a Supercharged B King blow a head gasket and the owner commented that all the head nuts were not very tight (APE 10mm studs). I'm wondering 2 things. 1, is this a stud issue or 2 should I be going to 12mm (1/2 inch studs). Or should I try stock bolts at much higher torque. As a side bar. I built a Triumph triple motor a long while back and I know a few techs in Triumph. They recommended I crank up the head bolts a lot more than stock, said they would take a load more angle (torque) than the manual. I did that and had no trouble. I also built a Nitrous busa back in 1999, with 120 shot of Nos. It was so new I had no spares. I reused the head gasket and bolts and we had no trouble and set a new British land speed record for flying 1/4 mile. There are a lot of guys out there that build far more Busa motors than me, so I'm just putting it out there for response. Thanks

 

[Oz22]

Aftermarket parts. Always a crap-shoot I am afraid.

 

[sixpack577]

Aftermarket parts. Always a crap-shoot I am afraid.

APE fasteners are generally high quality, and some of the best, not that you can't easily get new bad parts, nowdays especially, but the issue seems more in finding the magic number in extra head torque, which the turbo community has likely solved, and the op needs some boosted opinions...which I am of no help
lol

 

[Oz22]

APE fasteners are generally high quality, and some of the best, not that you can't easily get new bad parts, nowdays especially, but the issue seems more in finding the magic number in extra head torque, which the turbo community has likely solved, and the op needs some boosted opinions...which I am of no help
lol

lol, yeah, like I said, a crap shoot, and sometimes you roll a seven.

See that crack on the steering stem nut, I thought it was an expansion joint or something
BMW mechanics missed it completely when I went in complaining about a clunk in the front under brakes, I hadn't even noticed it then. The head mechanic sussed out the bike in front of me and said it was the floating disks, Normal. Then I had new tires fitted and another mechanic on a test ride figured it out. I mean it shouldn't be hard hey, so bloody obvious! That whimpy little nut is alloy, can you believe it! $70 for that Titanium replacement from a master nut and bolt manufacturer but I wasn't taking chances on another OEM one. The titanium one is nearly 3 times as deep as as the factory one. If the oem had more meat on it perhaps it wouldn't have split.

 

[202mphbusa]

This issue has arisen a few times over the years. I've used aftermarket head studs and nuts over the years on Busa's. I have noticed that the nuts are never as tight on a strip down as when first installed. Some rebuilds have been because of head gasket failure. Head studs have to have elasticity in them to cater for the expansion of the aluminium engine when hot. If the studs elasticity is insignificant then its going to pull the case threads and the head torque is going to back off. This may not be a problem with drag motors as they do not get as hot as circuit or top speed use. I have just had a Supercharged B King blow a head gasket and the owner commented that all the head nuts were not very tight (APE 10mm studs). I'm wondering 2 things. 1, is this a stud issue or 2 should I be going to 12mm (1/2 inch studs). Or should I try stock bolts at much higher torque. As a side bar. I built a Triumph triple motor a long while back and I know a few techs in Triumph. They recommended I crank up the head bolts a lot more than stock, said they would take a load more angle (torque) than the manual. I did that and had no trouble. I also built a Nitrous busa back in 1999, with 120 shot of Nos. It was so new I had no spares. I reused the head gasket and bolts and we had no trouble and set a new British land speed record for flying 1/4 mile. There are a lot of guys out there that build far more Busa motors than me, so I'm just putting it out there for response. Thanks

I would pull the studs clean the cases and reinstall them "properly" they were probably not seated correctly in the cases
I have never heard of APE studs stretching Loose
My two Motors never had, then I went 1/2 studs

Studs do not have elasticity for aluminum growth from what I know
Yield strength of the steel Bolts is so much higher than the aluminum

 

[michael parris heuberger]

I would pull the studs clean the cases and reinstall them "properly" they were probably not seated correctly in the cases
I have never heard of APE studs stretching Loose
My two Motors never had, then I went 1/2 studs

Studs do not have elasticity for aluminum growth from what I know
Yield strength of the steel Bolts is so much higher than the aluminum

Hi. I eas told not yo use XXX head studs use APE motor bolts.

 

[jellyrug]

This issue has arisen a few times over the years. I've used aftermarket head studs and nuts over the years on Busa's. I have noticed that the nuts are never as tight on a strip down as when first installed. Some rebuilds have been because of head gasket failure. Head studs have to have elasticity in them to cater for the expansion of the aluminium engine when hot. If the studs elasticity is insignificant then its going to pull the case threads and the head torque is going to back off. This may not be a problem with drag motors as they do not get as hot as circuit or top speed use. I have just had a Supercharged B King blow a head gasket and the owner commented that all the head nuts were not very tight (APE 10mm studs). I'm wondering 2 things. 1, is this a stud issue or 2 should I be going to 12mm (1/2 inch studs). Or should I try stock bolts at much higher torque. As a side bar. I built a Triumph triple motor a long while back and I know a few techs in Triumph. They recommended I crank up the head bolts a lot more than stock, said they would take a load more angle (torque) than the manual. I did that and had no trouble. I also built a Nitrous busa back in 1999, with 120 shot of Nos. It was so new I had no spares. I reused the head gasket and bolts and we had no trouble and set a new British land speed record for flying 1/4 mile. There are a lot of guys out there that build far more Busa motors than me, so I'm just putting it out there for response. Thanks

Only advice I can give you, is to re-torque them after a certain amount of running hours. That is because I have not modified Busa's so I don't know, and because you have no reference to work from.

When I worked for Mercedes, on the design end, that was pretty much precision engineering applied in the engine assembly plant. We determined the torque, plus the degree of bolt rotation after torque is achieved, both with stress strain calculation and confirmation in the lab. Those bolts were designed to be used only once and they were actually stretched past the elastic limit, slightly into the yield curve of the actual bolt metal. The exact lubricant specification applied on the bolt was part of the equation.

 

[Berlin Germany]

folks ?
seriously / honestly

the screws or stud bolts have never ever an expansion function.

even the 10 or 12 ape stud bolts are not designed as expansion screws.

that's why you can use the ape bolts + nuts or the original screws again and again with exactly the same torques.
my buddies turbo get 1.2 bars in max (380-420 ps) and the head gasket is and remains tight .

and the apes , been used in building the engine, are still the same - even after disassembling the head now the 3rd time.

so what shall this discussion about expansion ?

sheer panic causing ?

 

[jellyrug]

so what shall this discussion about expansion ?

Over here, we have little blue pills, which helps with that,

 

[powerfulone]

I would pull the studs clean the cases and reinstall them "properly" they were probably not seated correctly in the cases
I have never heard of APE studs stretching Loose
My two Motors never had, then I went 1/2 studs

Studs do not have elasticity for aluminum growth from what I know
Yield strength of the steel Bolts is so much higher than the aluminum

Sorry you're wrong! Studs have elasticity to maintain clamping pressure from cold to hot and reverse. The coefficient of expansion of aluminium is 3 times that of steel. Its nothing to do with Yield strength, that's a totally different subject. These studs have always been torques to spec into the cases first.

 

[powerfulone]

folks ?
seriously / honestly

the screws or stud bolts have never ever an expansion function.

even the 10 or 12 ape stud bolts are not designed as expansion screws.

that's why you can use the ape bolts + nuts or the original screws again and again with exactly the same torques.
my buddies turbo get 1.2 bars in max (380-420 ps) and the head gasket is and remains tight .

and the apes , been used in building the engine, are still the same - even after disassembling the head now the 3rd time.

so what shall this discussion about expansion ?

sheer panic causing ?

What's an expansion screw
I'm running 1.7 bar on some engines, maybe 12mm are the answer. But like I say Aluminium expands 3 times faster than steel per deg. so something has to give. The cylinders will expand around 0.2mm from 0-80 deg C, the stud will expand 0.06mm so it has to stretch, if this stretch is within its elastic limit it won't yield (of course the yield point is much longer than this small amount of stretch, so thats not an issue). But different steels have different elasticity. If the steel is too rigid it will pull the threads in the case instead and then all the grip on the gasket has gone. Yoshimura had Titanium head studs on their Gsxr's in the 80's, they blew a lot of head gaskets because Ti hardly expands at all. When I started in business in 1982 I built a Cb750 with a Russ Collins 1080 big bore. I made my own cylinder studs out of Silver steel. Total disaster, they just ripped the thread straight out of the crankcase. Lesson Learnt!
I'm not trying to cause any panic in any way. I was hoping to share knowledge with knowledgeable people!

 

[202mphbusa]

okay as usual I am completely wrong
Even tho I MAKE hardware and deal with yield and stretch of materials daily.
I guess I am just stupid!

 

[202mphbusa]

The coefficient of thermal expansion for steel is 0.00000645in/in/deg F. Doesn't sound like much but when you run out the numbers it comes to . 405504 ft/mile/deg.

 

[TonyM995]

Do you use assembly lube on the threads? Jelly rug mentioned this at the end of his comment.

ARP 100-9909 ARP Ultra Torque Fastener Assembly Lubricant | Summit Racing

Free Shipping - ARP Ultra Torque Fastener Assembly Lubricant with qualifying orders of $109. Shop Assembly Lubricant at Summit Racing.

www.summitracing.com

At the 10 minute mark he states “the lubricant is critical”. That’s what she said too lol. Also a great video to understand fasteners. 6:30 mark is the head stud part. I’d watch the entire thing though.

 

[Berlin Germany]

hey folks ?
seriously / honestly

expansion screw / bolt means that this screw / bolt, after being tightened with the prescribed torque (+ possible angle of rotation), no longer contracts to its original length after loosening, because it is loaded beyond its elastic limit (and thus stretched) and may not be used a second time,
because then there is a very high risk/probability that it will tear/break.

you have to pay close attention to whether a screw connection is within its elastic range or beyond its elastic limit !!!

yes - the screws for example connecting rod bearings stretch when tightened with the specified torque/angle of rotation,
which can also be easily measured,
but they remain in their elastic range, which means that after loosening/unscrewing they always go back to their original length and show no stretch.

you learn this connection at the university in mechanical engineering/materials science. ;-)

and

wherever expansion screws may be used in a vehicle, this must be clearly described in the manual and these screws must be purchased brand new and replaced .

and there is nothing about it in the manual(s) - no matter what Gen you have - expansions are not used anywhere.

 

[powerfulone]

Do you use assembly lube on the threads? Jelly rug mentioned this at the end of his comment.

ARP 100-9909 ARP Ultra Torque Fastener Assembly Lubricant | Summit Racing

Free Shipping - ARP Ultra Torque Fastener Assembly Lubricant with qualifying orders of $109. Shop Assembly Lubricant at Summit Racing.

www.summitracing.com

At the 10 minute mark he states “the lubricant is critical”. That’s what she said too lol. Also a great video to understand fasteners. 6:30 mark is the head stud part. I’d watch the entire thing though.

Exactly!

 

[202mphbusa]

hey folks ?
seriously / honestly

expansion screw / bolt means that this screw / bolt, after being tightened with the prescribed torque (+ possible angle of rotation), no longer contracts to its original length after loosening, because it is loaded beyond its elastic limit (and thus stretched) and may not be used a second time,
because then there is a very high risk/probability that it will tear/break.

you have to pay close attention to whether a screw connection is within its elastic range or beyond its elastic limit !!!

yes - the screws for example connecting rod bearings stretch when tightened with the specified torque/angle of rotation,
which can also be easily measured,
but they remain in their elastic range, which means that after loosening/unscrewing they always go back to their original length and show no stretch.

you learn this connection at the university in mechanical engineering/materials science. ;-)

and

wherever expansion screws may be used in a vehicle, this must be clearly described in the manual and these screws must be purchased brand new and replaced .

and there is nothing about it in the manual(s) - no matter what Gen you have - expansions are not used anywhere.

I have notes with every one of my 8 Carrillo rods measured length

 

[jellyrug]

but they remain in their elastic range, which means that after loosening/unscrewing they always go back to their original length and show no stretch.

As mentioned above, we go beyond the elastic limit, up the yield curve into the UTS part of the stress strain curve.

Anyway, that is what we use to do with your prime supplier Mercedes Benz, in your neck of the woods when I worked for them. Spent more time in Stuttgart than I would like to remember.

This is why that is so important:

1.) In part of an engine, there are an extensive range of harmonic vibration frequencies. Ask Kawasaki, why they had connection rod bolts loosten on the early ZX 14 engines. Simple answer is the bolts were within their elastic range, and the vibration frequency loostened the bolts.

2,) When we go past the elastic range, the threads of the fastener are distorted PERMANTLY, they never go back to their original shape. Because we now have a distorted thread pattern, the fastener is permanently locked and there is no risk of it loostening by engine vibrations. When you actually dissasemble one of these engines, it is very apparent, as it takes almost 360 degrees rotation for the bolt to lose its fastening interference. That is also why it can only be used once.

hey folks ?
seriously / honestly

expansion screw / bolt means that this screw / bolt, after being tightened with the prescribed torque (+ possible angle of rotation), no longer contracts to its original length after loosening, because it is loaded beyond its elastic limit (and thus stretched) and may not be used a second time,
because then there is a very high risk/probability that it will tear/break.

you have to pay close attention to whether a screw connection is within its elastic range or beyond its elastic limit !!!

3.) I think you should have another look at a stress strain curve, and see what happens in the upper section of the curve. You will see that you are wrong.

4.) Obviously, this does not apply to every fasterner, it applies only to critical areas in the engine.

 

[Berlin Germany]

As mentioned above, we go beyond the elastic limit, up the yield curve into the UTS part of the stress strain curve.
(...)

at e.g. the mercedes cars and at some of their engines perhaps yes at some places ,
but NO & NEVER at our busas !

none of the screws is fastened / torqued beyond their elastic limit .

that is for 100% sure - otherwise suzuki would have remarked that in the manuals that some screws / bolt are not allowed to be used twice .
however, this reference is not found in any of the manuals for the Hayabusa - regardless of the year of manufacture / what gen 1, 2 or 3.

so please stop comparing motorcycles and their nuts and bolts with those of cars.

personally, I don't know of any Japanese motorcycles that have expansion screws installed that can only be used once because they were loaded beyond their expansion limit when they were installed.

a good example is mercedes and their screws at some places in their (car)engines - there they use expansion screws - not over all but at some places and those are definitely marked in their manual(s) .

_____________________________________________

even the 1/2" ARP studs for the cylinder only get 80-100 Nm and that is not enough only to reach their elastic limit .
before that they would got ripped out of the alu (i suppose) !

 

[jellyrug]

at e.g. the mercedes cars and theis engines perhaps yes,
but NO at our busas !

that ist 100% sure - otherwise suzuki would have remarked that in the manuals that some screws / bolt are not allowed to be used twice .
however, this reference is not found in any of the manuals for the Hayabusa - regardless of the year of manufacture / what gen 1, 2 or 3.

so please stop comparing motorcycles and their nuts and bolts with those of cars.

personally, I don't know of any Japanese motorcycles that have expansion screws installed that can only be used once because they were loaded beyond their expansion limit when they were installed.

a good example is mercedes and their screws at some places in their engines - there they use expansion screws - not over all but at some places and those are definitely marked in their manual(s) .

It’s not called an expansion screw, just a normal connection rod bolt.

When you live and work in the automotive industry, there are a lot of things you won’t find in manuals. There are a lot of tricks, known in the factory and taught to the service technicians which never find their way into the shop manuals.

I use to help with those and a lot of those manuals are written by folks who are good at English, or German, or Spanish, but they have never held a wrench in their hands.

How many Hayabusa engines have you rebuilt, and how many miles on the rebuilt engines?

So when you rebuild a Hayabusa motor, do you just put all the old parts back into it again?

Anyway, watch the video again, he talks about the same thing, albeit in less detail.