head bolts

[tErbo b00st]

According to you there is. Since their will be a standard deviation on everything to include the torque specs, the failure rates should be even higher with your "hypothesis". Facts are, that the 56 lb/ft is more than enough to make the HG survive 225k miles and that was beating the crap out of that motor. I should know as I am the owner of that engine.

That was through the mountain climbs of Georgia (Atlanta to Chattanooga 5 miles worth), Miami heat and humidity, South Dakota snow dumps and Minnesota freezer temps. Never once, a HG issue. Even with the A/C cranking.

How do do you think I do think this? Every engine/car is different...you seem to think because you did it everyone can. This is far from the truth

I do!

but seems like you don't.

HG studs are in fact torqued to yield. They have to be. As that is where their preload will be maximized, leveraging the studs tensile strength without failure. You can not Torque to yield bolts as you have the rotating force interfering with a proper torque reading.

"HG studs are in fact torqued to yeild" "you can not torque to yield"


WTF :aigo:

 

[tErbo b00st]

generally speaking oem head studs are not torque to yield bolts. Aftermarket (ARP) are torque to yield.

"torque to yield" means that you can torque them to yield

I do not know, but will vernture to guess oem 7m head studs are NOT torque to yield.

 

[figgie]

generally speaking oem head studs are not torque to yield bolts. Aftermarket (ARP) are torque to yield.

"torque to yield" means that you can torque them to yield

I do not know, but will vernture to guess oem 7m head studs are NOT torque to yield.

ummm

OEM 7M = Head BOLTS not stud. Hence why I worded the sentence the way I did

See

HG studs are in fact torqued to yield....

You can not Torque to yield bolts...

Two seperate items and since there was never OEM studs for the 7M, that implicitly means that the HG studs are aftermarket.

 

[tErbo b00st]

ummm

OEM 7M = Head BOLTS not stud. Hence why I worded the sentence the way I did

See



Two seperate items and since there was never OEM studs for the 7M, that implicitly means that the HG studs are aftermarket.

Oh right, I misread...sorry about that

I still fail to see how this supports your argument.

 

[figgie]

this is not an arguement or debate.

56 lbs/ft on the bolts will not cause a HG failure. Remove EGR or increase boost to Fuel cut off or close to it (inertia or the fuel etc) or Cold air intake mod with the engine breathing the super "cold air" that comes after the radiator or a combination of all three. The HG will have no choice but to fail. Detonation at low load conditions, higher probability of detonation by breathing the nice cool post radiator air, fuel has mass and even if the TCCS shuts the party down, the fuel will probably still be injectected at a less quantity (read lean condition). by themselves they will take an HG down without an issue. Combined. Defeintely will take the HG out.

It is not a torque issue. It is literally an education issue.

 

[tErbo b00st]

ummm

OEM 7M = Head BOLTS not stud. Hence why I worded the sentence the way I did

See



Two seperate items and since there was never OEM studs for the 7M, that implicitly means that the HG studs are aftermarket.

this is not an arguement or debate.

56 lbs/ft on the bolts will not cause a HG failure. Remove EGR or increase boost to Fuel cut off or close to it (inertia or the fuel etc) or Cold air intake mod with the engine breathing the super "cold air" that comes after the radiator or a combination of all three. The HG will have no choice but to fail. Detonation at low load conditions, higher probability of detonation by breathing the nice cool post radiator air, fuel has mass and even if the TCCS shuts the party down, the fuel will probably still be injectected at a less quantity (read lean condition). by themselves they will take an HG down without an issue. Combined. Defeintely will take the HG out.

It is not a torque issue. It is literally an education issue.

A higher (properly) torqued head will be able to withstand more detonation (ie detonation does not always mean broken engine). Most engines will encounter knock/detonation at some point...it's the engine's ability to handle that knock that determines whether the engine will be reliable. So yea...your right...but your not looking at the whole picture.

And there are plenty of stock 7M's that have had BHG. An intake should not create a bhg.

A properly running fuel cut cuts enough fuel to the point where it is too lean to burn at all...hence no detonation

 

[figgie]

A higher (properly) torqued head will be able to withstand more detonation (ie detonation does not always mean broken engine). Most engines will encounter knock/detonation at some point...it's the engine's ability to handle that knock that determines whether the engine will be reliable. So yea...your right...but your not looking at the whole picture.

And there are plenty of stock 7M's that have had BHG. An intake should not create a bhg.

A properly running fuel cut cuts enough fuel to the point where it is too lean to burn at all...hence no detonation

The head? You mean HeadGASKET. No. That is the property of the HG material. Hence why Toyota went with a copper ring for the new revision of the 7m HG instead of the old material they were using prior.


just like there are plenty of LS7 that have BHG, or thrown a Ti rod, or 3uz that have HG, or 4g63 with BHG. The question is from a statistical model, what percentile v. the other engine was the 7m failing. No one has those numbers and as we have seen, misinformation tends to propagate at staggering rates due to ineptitude, ignorance, sillyness and/or all of the above.

see the 7m is a BHG gnome, yet I and countless others have not had it. It is not by luck mind you.

EGR removal is SMART!
Electric fans release x HP (well within standard deviation of ALL dynos).
Charcoal canister removed to look good but no vent for the highly volatile gasoline/petrol vapors.
Racing seats without a Cage.
Anti-lag systems are cool (yet no thought about all that energy that moves the pig of a supra now moving 1 lbs worth of turbo compressor wheel).


the list of idiocies is endless.

 

[tErbo b00st]

The head? You mean HeadGASKET. No. That is the property of the HG material. Hence why Toyota went with a copper ring for the new revision of the 7m HG instead of the old material they were using prior.


just like there are plenty of LS7 that have BHG, or thrown a Ti rod, or 3uz that have HG, or 4g63 with BHG. The question is from a statistical model, what percentile v. the other engine was the 7m failing. No one has those numbers and as we have seen, misinformation tends to propagate at staggering rates due to ineptitude, ignorance, sillyness and/or all of the above.

see the 7m is a BHG gnome, yet I and countless others have not had it. It is not by luck mind you.

EGR removal is SMART!
Electric fans release x HP (well within standard deviation of ALL dynos).
Charcoal canister removed to look good but no vent for the highly volatile gasoline/petrol vapors.
Racing seats without a Cage.
Anti-lag systems are cool (yet no thought about all that energy that moves the pig of a supra now moving 1 lbs worth of turbo compressor wheel).


the list of idiocies is endless.

how many times do I have to say that just because "some people" havn't experienced it it isn't a problem. There is also no hard data supporting that 4g63s have crank walk problems...but everyone know that the 7 bolt engine has these problems. Your mighty totoya engineers aren't god's to where they can not make a mistake.

When typical oem torquing is around 80-90 ftlbs and the toyota motor, that has numerous bhg problems, is around 60...something is most likely wrong.


anndd...are you suggesting that anti-lag systems are worthless?

 

[soup]

I'm enjoying the read so far. You guys have both raised some good points.

I'm sure you both know that parts are designed for assumed loads and assumed cycles. I'm sure you both also know that all parts and assemblies have a tolerance. and I'm sure you both also know that what's crunched out on paper should be validated empiracally.

I know jack $hit about combustion theory and internal combustion engine design. but I can make assumptions. I assume the Engineer's at Toyota came up XX pressure from combustion.

They then figured out what's the minimum force the head bolts need to exert on the head to prevent it from lifting off the block, this force is inflated by some amount such that the preload torque (56 ft-lbs in the 7M's case) will create a force that is higher than anything that is expected to be seen from normal driving conditions. I don't know if they design it as a ttyl or keep it in the elastic region, feel free to chime in on what you think/know and WHY.

I would also think that the gasket material is selected to perform to some maximum temperature and some maximum pressure. The torque on the headbolts/studs would affect the gasket's ability to maintain said pressure due to friction, no?

I mentioned that the Engineer's come up with a life cycle for the engine/parts. This load cycle will have a mix of daily and spirited driving, and gives them the engine/parts design life/maintenance schedule. Everyone's actual driving cycle is different, and when you modify a car you're going to change its loads and expected life.

The 7M is 20 years old! It's going to break, that's the nature of fatigue. Some parts get lucky and might even get an infinite life, greater than a million cycles or whatever. some parts are going to be at the other end of the curve and fail early. That's just the way it is. Engineer's aren't all knowing and make mistakes, i mean assumptions .

Fracture, fatigue and mechanical reliability is still pretty new. The goal is to one day be able to accurately come up a design method that will perform exactly as desired.

Don't harp on my English or grammar, no body's perfect. Make your comments constructive and provide proof or state your assumptions.




To the guy asking if he should retorque his head. IMO, I'd retorque. But I'm not holding a gun to your head. Educate yourself with the readings people have posted and make an informed decision, it's your car.

 

[tErbo b00st]

The head? You mean HeadGASKET. No. That is the property of the HG material. Hence why Toyota went with a copper ring for the new revision of the 7m HG instead of the old material they were using prior.


just like there are plenty of LS7 that have BHG, or thrown a Ti rod, or 3uz that have HG, or 4g63 with BHG. The question is from a statistical model, what percentile v. the other engine was the 7m failing. No one has those numbers and as we have seen, misinformation tends to propagate at staggering rates due to ineptitude, ignorance, sillyness and/or all of the above.

see the 7m is a BHG gnome, yet I and countless others have not had it. It is not by luck mind you.

EGR removal is SMART!
Electric fans release x HP (well within standard deviation of ALL dynos).
Charcoal canister removed to look good but no vent for the highly volatile gasoline/petrol vapors.
Racing seats without a Cage.
Anti-lag systems are cool (yet no thought about all that energy that moves the pig of a supra now moving 1 lbs worth of turbo compressor wheel).


the list of idiocies is endless.

I'm enjoying the read so far. You guys have both raised some good points.

I'm sure you both know that parts are designed for assumed loads and assumbed cycles. I'm sure you both also know that all parts and assemblies have a tolerance. and I'm sure you both also know that what's crunched out on paper should be validated empiracally.

I know jack $hit about combustion theory and internal combustion engine design. but I can make assumptions. I assume the Engineer's at Toyota came up XX pressure from combustion.

They then figured out what's the minimum force the head bolts need to exert on the head to prevent it from lifting off the block, this force is inflated by some amount such that the preload torque (56 ft-lbs in the 7M's case) will create a force that is higher than anything that is expected to be seen from normal driving conditions. I don't know if they design it as a ttyl or keep it in the elastic region, feel free to chime in on what you think/know and WHY.

I would also think that the gasket material is selected to perform to some maximum temperature and some maximum pressure. The torque on the headbolts/studs would affect the gasket's ability to maintain said pressure due to friction, no?

I mentioned that the Engineer's come up with a life cycle for the engine/parts. This load cycle will have a mix of daily and spirited driving, and gives them the engine/parts design life/maintenance schedule. Everyone's actual driving cycle is different, and when you modify a car you're going to change its loads and expected life.

The 7M is 20 years old! It's going to break, that's the nature of fatigue. Some parts get lucky and might even get an infinite life, greater than a million cycles or whatever. some parts are going to be at the other end of the curve and fail early. That's just the way it is. Engineer's aren't all knowing and make mistakes, i mean assumptions .

Don't harp on my English or grammar, no body's perfect. Make your comments constructive and provide proof or state your assumptions.

I agree with what most of what your saying . But just like we have seen with many many other automotive components sometimes those calculations are performed incorrectly or assumptions were made that should not be made. Some assumptions like detonation is the only thing that causes a bhg :sarcasm:

 

[Poodles]

There isn't a single torque to yeild fastener on a 7M...

 

[figgie]

how many times do I have to say that just because "some people" havn't experienced it it isn't a problem.

The issue is not "some" because sooner or later some becomes none. The issue is the internet makes it seem like it is all when it is not. I know of about a dozen folks that never had a problem, in real life. Why don't we hear about them? Because they are driving the cars without a problem.

There is also no hard data supporting that 4g63s have crank walk problems...but everyone know that the 7 bolt engine has these problems. Your mighty totoya engineers aren't god's to where they can not make a mistake.

When typical oem torquing is around 80-90 ftlbs and the toyota motor, that has numerous bhg problems, is around 60...something is most likely wrong.


anndd...are you suggesting that anti-lag systems are worthless?

Typical?

Bullshit. the 2jz specs for thier headbolts is 25 lbs the first pass then and additional 90 degrees pass on the 2nd pass and finishing off the tightening sequence by adding another 90 degree worth of turn at the third and final pass.

Again beliefs are not facts. What you believe is not fact. I find it quite comical that somehow, in just about every negative situation for the MKIII Supra, I am always the "exception" to the rule. I must be a lucky guy OR there is something that I am doing that prevents the failure.... wonder what that could be.......................


ALS system on a street car are worthless.

ALS on a WRC are NEEDED.
ALS in drag racing, on an auto tranny, worthless. On a manual, only way to build boost off the line.

Again though, as long as the user understands that the turbo becomes a chuck away part at that point. There is a reason why WRC monitors EGTs under ALS and that is to make sure they don't make the compressor section of the turbo a molten puddle.

 

[CyFi6]

There isn't a single torque to yeild fastener on a 7M...

This...

Im not going to get in on this "argument", but i do see a lot of points i disagree on. And i have lost a little bit of respect for you figgie seeing how you have been responding...

 

[figgie]

This...

Im not going to get in on this "argument", but i do see a lot of points i disagree on. And i have lost a little bit of respect for you figgie seeing how you have been responding...

and that is.....

I provide FACTS. Lost respect. I was never looking for it in the first place.

but since it was mentioned.

I'll leave this thread for you guys to bicker about ad naseum.

 

[tErbo b00st]

ALS system on a street car are worthless.

ALS on a WRC are NEEDED.
ALS in drag racing, on an auto tranny, worthless. On a manual, only way to build boost off the line.

Again though, as long as the user understands that the turbo becomes a chuck away part at that point. There is a reason why WRC monitors EGTs under ALS and that is to make sure they don't make the compressor section of the turbo a molten puddle.

completely agree...thanks for clarifying because i was about to completely write off everything have said, hah

 

[adampecush]

Originally Posted by tErbo b00st
HG bolts are not suppose to be torqued to their yeild. If you knew anything about material properties and fatigue crack propogation, in tandem with cycling cylinder pressures, you would know this. If you tighten something to it's yield torque that means as soon as any pressure is exerted on it, it will experience plastic deformation. This is bad if you weren't sure. Deformation coupled with cyclic fatigue is also bad.

Your fundamental understanding of materials is somewhat lacking. If you preload a steel bolt into the yield range, it will not deform further unless it is subjected to a load higher than that already achieved by the preload. Thus, even if not torqued to yield, it would deform as a result of a sufficiently large applied load.

Originally Posted by figgie

HG studs are in fact torqued to yield. They have to be. As that is where their preload will be maximized, leveraging the studs tensile strength without failure. You can not Torque to yield bolts as you have the rotating force interfering with a proper torque reading.

Unless the stud shanks are of a reduced cross-section relative to the threaded regions, the fasteners are NOT torque to yield. If you torque a constant diameter fastener to yield, you are going to yield it only in the exposed threaded regions due to their inherent reduced cross-section. This results in high localized strain/deformation, a very dangerous condition with respect to fatigue.

A reduced diameter shank TTY fastener will spread the deformation out over the shank length, resulting in relatively small local strains/deformation.

You can also have TTY bolts and studs, the configuration of the fastener means nothing. Here are some TTY bolts if you don't beleive me. Thread resistance and bolt clamping surface resistance are both taken into account when specifying an adequate torque or torque-angle.