In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
What happens if you reuse cylinder head bolts?
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Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
Seems like we're doing fewer head gaskets now...
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
Seems like we're doing fewer head gaskets now...
I cannot imagine doing major work like a head gasket and cheaping out on parts!
Crazytown...
Crazytown...
Originally Posted by rooflessVW
Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
Seems like we're doing fewer head gaskets now...
TTY bolts hold their clamping force for longer, they have less mechanical strain and fatigue less than regular bolts (of same size, similar cost target) when used correctly.
One workaround for regular bolts is to use more or oversize. Compression washers can also help with regular bolts (they add a bit of elasticity to the clamping force), but are not economically reliable under the high forces required for clamping a cylinder head down.
Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
Seems like we're doing fewer head gaskets now...
TTY bolts hold their clamping force for longer, they have less mechanical strain and fatigue less than regular bolts (of same size, similar cost target) when used correctly.
One workaround for regular bolts is to use more or oversize. Compression washers can also help with regular bolts (they add a bit of elasticity to the clamping force), but are not economically reliable under the high forces required for clamping a cylinder head down.
Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
People who have no clue as to a valid engineering reason for something should not fabricate one in their own head and post it to the Internet.
Where did you get your engineering degree?
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
People who have no clue as to a valid engineering reason for something should not fabricate one in their own head and post it to the Internet.
Where did you get your engineering degree?
MB used to publish a max length spec for stretch bolts so those could be reused with no problem if it was under the max. If there is no spec I don't reuse them.
I was a High School Senior 69 - 70 . Went to school 1/2 day .Worked 1/2 day at the dodge dealer as a shop flunky / go-fer .
At that time it was SOP to re-use head and all the other bolts , as long as they were not damaged .
Only in the last 5 years have I heard of TTY bolts .
Anyone wish to enlighten me why the change ? Does it have anything to do do with aluminum heads and / or blocks ?
Thanks ,
At that time it was SOP to re-use head and all the other bolts , as long as they were not damaged .
Only in the last 5 years have I heard of TTY bolts .
Anyone wish to enlighten me why the change ? Does it have anything to do do with aluminum heads and / or blocks ?
Thanks ,
Yes, it can be related to the use of aluminum cylinder heads but it is also related to the specific type of head gasket being used. Overall it provides a much more consistent clamping force over the expected operating temperatures.
I tried to find a good reference and this seems about as good as any other:
https://www.felpro.com/technical/tecblogs/proper-installation-use-t-t-y-bolts.html
You can still generally reuse TTY bolts as long as you know what is a maximum permitted length (or sometimes a diameter) for the bolt.
I tried to find a good reference and this seems about as good as any other:
https://www.felpro.com/technical/tecblogs/proper-installation-use-t-t-y-bolts.html
You can still generally reuse TTY bolts as long as you know what is a maximum permitted length (or sometimes a diameter) for the bolt.
Originally Posted by kschachn
Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
People who have no clue as to a valid engineering reason for something should not fabricate one in their own head and post it to the Internet.
Where did you get your engineering degree?
Yup, the use of TTY bolt has nothing to do with cheapining out or padding the repair bills for the dealerships.
For cylinder heads, TTY bolts have a very good advantage. Since they are in the elastic range, they can elongate and shrink with the head and gasket as the temperatures changes and keep a more consistent clamping force on the whole assembly.
It is not a coincidence head gasket problems are occuring much less and at much higher odometer readings. TTY bolts are part of that.
Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
People who have no clue as to a valid engineering reason for something should not fabricate one in their own head and post it to the Internet.
Where did you get your engineering degree?
Yup, the use of TTY bolt has nothing to do with cheapining out or padding the repair bills for the dealerships.
For cylinder heads, TTY bolts have a very good advantage. Since they are in the elastic range, they can elongate and shrink with the head and gasket as the temperatures changes and keep a more consistent clamping force on the whole assembly.
It is not a coincidence head gasket problems are occuring much less and at much higher odometer readings. TTY bolts are part of that.
If the OP is asking about his GM LM7.....No such spec exist for reusing them & the FSM specifically states to use new head bolts.
Most head gasket failures these days NOT caused by overheating or thread pull-out can be traced back to "scrubbing" of the head gasket from different expansion rates between the block & cylinder head. The LLY Duramax is a perfect example of this phenomenon.
Most head gasket failures these days NOT caused by overheating or thread pull-out can be traced back to "scrubbing" of the head gasket from different expansion rates between the block & cylinder head. The LLY Duramax is a perfect example of this phenomenon.
If no spec is available then no I do not reuse them in any case. Does the Duramax have a Teflon coating on the HG?
Originally Posted by Trav
If no spec is available then no I do not reuse them in any case. Does the Duramax have a Teflon coating on the HG?
Good question Trav, Wish I had a definitive answer? However.....The updated LBZ gaskets appear to have a selective Elastomer coating on the cylinder head side & a solid Elastomer coating on the block side, I guess the core could have a Teflon coating?. They are also riveted together in several places vs the crimped gaskets used on the LLY.
The updated gaskets require a lower head bolt torque for whatever that's worth.
What I can attest to is.....The LBZ gaskets do not seem to fail from scrub, I'm guessing it's a combination of better materials & lower head bolt torque?
Your thoughts on this subject are appreciated Trav......
If no spec is available then no I do not reuse them in any case. Does the Duramax have a Teflon coating on the HG?
Good question Trav, Wish I had a definitive answer? However.....The updated LBZ gaskets appear to have a selective Elastomer coating on the cylinder head side & a solid Elastomer coating on the block side, I guess the core could have a Teflon coating?. They are also riveted together in several places vs the crimped gaskets used on the LLY.
The updated gaskets require a lower head bolt torque for whatever that's worth.
What I can attest to is.....The LBZ gaskets do not seem to fail from scrub, I'm guessing it's a combination of better materials & lower head bolt torque?
Your thoughts on this subject are appreciated Trav......
Originally Posted by KrisZ
Originally Posted by kschachn
Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
People who have no clue as to a valid engineering reason for something should not fabricate one in their own head and post it to the Internet.
Where did you get your engineering degree?
Yup, the use of TTY bolt has nothing to do with cheapining out or padding the repair bills for the dealerships.
For cylinder heads, TTY bolts have a very good advantage. Since they are in the elastic range, they can elongate and shrink with the head and gasket as the temperatures changes and keep a more consistent clamping force on the whole assembly.
It is not a coincidence head gasket problems are occuring much less and at much higher odometer readings. TTY bolts are part of that.
Its funny when some folks read things into someone elses post. I'm agreeing that TTY bolts are necessary, I did not elaborate where the cheaping out was done.
And why the bolts are needed. Please don't tell me what I know or don't know.
FYI, there are some very famous head gasket failure cases, that ended up as major court cases and recalls. Just do a simple search.
Originally Posted by kschachn
Originally Posted by Exhaustgases
In the old days things were done correctly, no need for TTY bolts. Things done cheapy now and TTY is a great way for the dealer to make more $ on the repairs, it helps pad the parts bill. Car things are not better now just cheaper to build, there is no money in making it last forever.
People who have no clue as to a valid engineering reason for something should not fabricate one in their own head and post it to the Internet.
Where did you get your engineering degree?
Yup, the use of TTY bolt has nothing to do with cheapining out or padding the repair bills for the dealerships.
For cylinder heads, TTY bolts have a very good advantage. Since they are in the elastic range, they can elongate and shrink with the head and gasket as the temperatures changes and keep a more consistent clamping force on the whole assembly.
It is not a coincidence head gasket problems are occuring much less and at much higher odometer readings. TTY bolts are part of that.
Its funny when some folks read things into someone elses post. I'm agreeing that TTY bolts are necessary, I did not elaborate where the cheaping out was done.
And why the bolts are needed. Please don't tell me what I know or don't know.
FYI, there are some very famous head gasket failure cases, that ended up as major court cases and recalls. Just do a simple search.
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Good thread from back in the day...
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2009508
I've still got one of moribundman's Audi head bolts in my desk drawer at work I think.
Torque to yield, on cylinder heads in a mass manufacturing process makes so much more sense to me than torque...in industry, lets say turbines and heavy equipment, it's strain that you tighten to, not torque...strain is the elongation of the effective area of the fastener.
mori's audi, they had a specific technique for stopping weeping head gaskets which involved backing off the TTY bolts, and re-tightening them.
I took the bolt, XRFed it to get a material spec measured the threads and the effective length, and you could get at least three uses before hitting the bad end of the stress strain curve.
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2009508
I've still got one of moribundman's Audi head bolts in my desk drawer at work I think.
Torque to yield, on cylinder heads in a mass manufacturing process makes so much more sense to me than torque...in industry, lets say turbines and heavy equipment, it's strain that you tighten to, not torque...strain is the elongation of the effective area of the fastener.
mori's audi, they had a specific technique for stopping weeping head gaskets which involved backing off the TTY bolts, and re-tightening them.
I took the bolt, XRFed it to get a material spec measured the threads and the effective length, and you could get at least three uses before hitting the bad end of the stress strain curve.
Originally Posted by Exhaustgases
Its funny when some folks read things into someone elses post. I'm agreeing that TTY bolts are necessary, I did not elaborate where the cheaping out was done.
And why the bolts are needed. Please don't tell me what I know or don't know.
FYI, there are some very famous head gasket failure cases, that ended up as major court cases and recalls. Just do a simple search.
You can elaborate now, so where is the "cheaping out" occurring in regards to TTY head bolts?
Its funny when some folks read things into someone elses post. I'm agreeing that TTY bolts are necessary, I did not elaborate where the cheaping out was done.
And why the bolts are needed. Please don't tell me what I know or don't know.
FYI, there are some very famous head gasket failure cases, that ended up as major court cases and recalls. Just do a simple search.
You can elaborate now, so where is the "cheaping out" occurring in regards to TTY head bolts?
Originally Posted by Shannow
Good thread from back in the day...
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2009508
I've still got one of moribundman's Audi head bolts in my desk drawer at work I think.
Torque to yield, on cylinder heads in a mass manufacturing process makes so much more sense to me than torque...in industry, lets say turbines and heavy equipment, it's strain that you tighten to, not torque...strain is the elongation of the effective area of the fastener.
mori's audi, they had a specific technique for stopping weeping head gaskets which involved backing off the TTY bolts, and re-tightening them.
I took the bolt, XRFed it to get a material spec measured the threads and the effective length, and you could get at least three uses before hitting the bad end of the stress strain curve.
Thanks for the link. I thought most TTY head bolts are still in the elastic range, but at the verge of going into the plastic range. Turns out they can be in the plastic range and not yield to failure and some can be re-used. Crazy good engineering and metallurgy.
Good thread from back in the day...
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2009508
I've still got one of moribundman's Audi head bolts in my desk drawer at work I think.
Torque to yield, on cylinder heads in a mass manufacturing process makes so much more sense to me than torque...in industry, lets say turbines and heavy equipment, it's strain that you tighten to, not torque...strain is the elongation of the effective area of the fastener.
mori's audi, they had a specific technique for stopping weeping head gaskets which involved backing off the TTY bolts, and re-tightening them.
I took the bolt, XRFed it to get a material spec measured the threads and the effective length, and you could get at least three uses before hitting the bad end of the stress strain curve.
Thanks for the link. I thought most TTY head bolts are still in the elastic range, but at the verge of going into the plastic range. Turns out they can be in the plastic range and not yield to failure and some can be re-used. Crazy good engineering and metallurgy.
Last edited:
Originally Posted by KrisZ
Thanks for the link. I thought most TTY head bolts are still in the elastic range, but at the verge of going into the plastic range. Turns out they can be in the plastic range and not yield to failure and some can be re-used. Crazy good engineering and metallurgy.
Right, they wouldn't be yielding if there wasn't plastic deformation.
Thanks for the link. I thought most TTY head bolts are still in the elastic range, but at the verge of going into the plastic range. Turns out they can be in the plastic range and not yield to failure and some can be re-used. Crazy good engineering and metallurgy.
Right, they wouldn't be yielding if there wasn't plastic deformation.
Originally Posted by clinebarger
Originally Posted by Trav
If no spec is available then no I do not reuse them in any case. Does the Duramax have a Teflon coating on the HG?
Good question Trav, Wish I had a definitive answer? However.....The updated LBZ gaskets appear to have a selective Elastomer coating on the cylinder head side & a solid Elastomer coating on the block side, I guess the core could have a Teflon coating?. They are also riveted together in several places vs the crimped gaskets used on the LLY.
The updated gaskets require a lower head bolt torque for whatever that's worth.
What I can attest to is.....The LBZ gaskets do not seem to fail from scrub, I'm guessing it's a combination of better materials & lower head bolt torque?
Your thoughts on this subject are appreciated Trav......
There was I thread some time ago where someone posted about the benefits of studs vs bolts, this exact question came in my mind regarding dissimilar metals and coated gaskets and it appears tighter isn't necessarily better when it comes to this type of gasket.
Having been in this business 47 years now I was working when aluminum heads came into mainstream production and saw the early issues with gaskets and cracking of the heads in the water jacket area.
I seems the manufacturers were trying to control expansion of the aluminum instead of letting it expand and contract and creating a gasket that could cope with it.
MLS coated gaskets seem to be the answer, I have seen them coated on both sides or in the middle layer on both sides only, both seem to work equally well, lowering the torque will allow the parts to move easier without damaging the coating.
The worst are the open deck engines like Subaru and even worse iron block aluminum head open blocks like some early Peugeot, I never understood why Subaru went from a good solid closed deck that had few if any HG failures to an open deck with nothing but failures and stayed with it. Peugeot did go closed deck and eliminated the problem.
As far as the stretch bolt thing goes the one thing that is not being taken into account in this discussion is how far the manufacture takes the bolt when installed.
VW for example stretches some of them to the point of almost snapping when first installed, the dog bone mount is a good example. tighten it 50nm + 90 degrees twice and there is a good chance you will have half the bolt in your hand.
Tighten it 50nm and go 45 degrees and you can reuse it multiple times (been there done that) or just replace the 8.8 grade stretch with 10.9 and tighten to 50nm and put blue loctite on them (even better).
On some of the others like the head bolts and subframe to body they are nowhere near maxed out. MB has always been conservative from my experience and most can be reused multiple times but unless you have the spec or know from experience how would you know, that's the reason I toss most of them.
Originally Posted by Trav
If no spec is available then no I do not reuse them in any case. Does the Duramax have a Teflon coating on the HG?
Good question Trav, Wish I had a definitive answer? However.....The updated LBZ gaskets appear to have a selective Elastomer coating on the cylinder head side & a solid Elastomer coating on the block side, I guess the core could have a Teflon coating?. They are also riveted together in several places vs the crimped gaskets used on the LLY.
The updated gaskets require a lower head bolt torque for whatever that's worth.
What I can attest to is.....The LBZ gaskets do not seem to fail from scrub, I'm guessing it's a combination of better materials & lower head bolt torque?
Your thoughts on this subject are appreciated Trav......
There was I thread some time ago where someone posted about the benefits of studs vs bolts, this exact question came in my mind regarding dissimilar metals and coated gaskets and it appears tighter isn't necessarily better when it comes to this type of gasket.
Having been in this business 47 years now I was working when aluminum heads came into mainstream production and saw the early issues with gaskets and cracking of the heads in the water jacket area.
I seems the manufacturers were trying to control expansion of the aluminum instead of letting it expand and contract and creating a gasket that could cope with it.
MLS coated gaskets seem to be the answer, I have seen them coated on both sides or in the middle layer on both sides only, both seem to work equally well, lowering the torque will allow the parts to move easier without damaging the coating.
The worst are the open deck engines like Subaru and even worse iron block aluminum head open blocks like some early Peugeot, I never understood why Subaru went from a good solid closed deck that had few if any HG failures to an open deck with nothing but failures and stayed with it. Peugeot did go closed deck and eliminated the problem.
As far as the stretch bolt thing goes the one thing that is not being taken into account in this discussion is how far the manufacture takes the bolt when installed.
VW for example stretches some of them to the point of almost snapping when first installed, the dog bone mount is a good example. tighten it 50nm + 90 degrees twice and there is a good chance you will have half the bolt in your hand.
Tighten it 50nm and go 45 degrees and you can reuse it multiple times (been there done that) or just replace the 8.8 grade stretch with 10.9 and tighten to 50nm and put blue loctite on them (even better).
On some of the others like the head bolts and subframe to body they are nowhere near maxed out. MB has always been conservative from my experience and most can be reused multiple times but unless you have the spec or know from experience how would you know, that's the reason I toss most of them.
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