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guys - what is a triple square tool? About to do this job. Need tips and info. TIA
It's called a "XZN" tool.
Do yourself a favor and buy a Hazet 8808-8. This is a tool that your grandkids kids kids will be able to still use on their electric car.
I've been using the same one for....30 years?
I can't wear it out....and because it doesn't deteriorate with use, it has a very low rate of "rounding out the fasteners."
And the "new version" has Titanium Nitrate on it, making it more durable!
I've also got 3 or 4 Snap-off versions, which must be replaced after every set of heads...
....along with a handful of fasteners.
(These are left over from 914 C/V joint bolt days...and you had to have 3-4 of them to finish some jobs. Sometimes, a non-thinking mechanic will grab one of these out of my box to pull the cam cap bolts on a 928 engine. It's almost comical to listen to the swearing.)
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
I reused head bolts before on my S4. End up with a steady oil leak from the passenger side head on the back where the oil feed passage from the block feeds the head. Took the engine out again, replaced both headgaskets again and got a new head bolt set. Leak went away. There was nothing wrong with the headgasket so I figured the bolt must have yielded and wasn't taking the proper amount of torque anymore, so took it apart and replaced all of them. Back then they were about 15-17 bucks I think (10 years ago). They are not going to get any cheaper so replace them.
I would personally take the engine out. The head is heavy and you don't want to gouge the surface going into the engine bay. Plus if I remember right when I took the head off the drivers side the brake booster was in the way of one of the head bolts. Also the shock towers will be in the way of getting a wrench down there to take the cam caps off and you don't want to damage those bolts, they were about 10 bucks each back then not sure what they cost now. Take the engine out get the Hazet socket Greg mentioned above to take the cam cap bolts off without damaging them (that's the one I used per his recommendation back then and still have it, don't buy the cheap ones at your auto parts store it cost me 3 to 4 cam cap bolts...), have to make sure the tool is fully seated in the bolt heads before you break them loose with a breaker bar, may want to clean the gunk out with Q-tips before you insert the tool.
It's common to see these head bolts suffering from Hydrogen Embrittlement, .
High strength steels are indeed susceptible to Hydrogen Embrittlement - perhaps you might be kind enough to advise what you saw that led you to understand that such degradation had happened.
It's called a "XZN" tool.
Do yourself a favor and buy a Hazet 8808-8. This is a tool that your grandkids kids kids will be able to still use on their electric car.
I've been using the same one for....30 years?
I can't wear it out....and because it doesn't deteriorate with use, it has a very low rate of "rounding out the fasteners."
And the "new version" has Titanium Nitrate on it, making it more durable!
I've also got 3 or 4 Snap-off versions, which must be replaced after every set of heads...
....along with a handful of fasteners.
(These are left over from 914 C/V joint bolt days...and you had to have 3-4 of them to finish some jobs. Sometimes, a non-thinking mechanic will grab one of these out of my box to pull the cam cap bolts on a 928 engine. It's almost comical to listen to the swearing.)
High strength steels are indeed susceptible to Hydrogen Embrittlement - perhaps you might be kind enough to advise what you saw that led you to understand that such degradation had happened.
1. I had a few used bolts snap off when tightened. This concerned me greatly, as in the late '70's Porsche changed the head studs on the 911's to unpained/coated Dilivar. These things broke very frequently. If you tried to re-use them in an overhaul, you could sometimes walk away from the engine after torquing the heads and hear the studs shear.
2. When tightening 928 heads with old bolts (and sometimes with studs), I noticed quite a bit of difference between the effort to angle torque different used bolts/studs.
3. So, I bought a torque wrench that measured both angles and foot pounds.
When set to an angle, once it reaches that angle, this tool automatically tells the user (as soon as you remove the pressure) how many ft.lbs. it took to achieve that angle.
Once I could see that data, it was pretty simple to logic out that there was something radically wrong. (50% variance was common.)
Buying new head bolts solved this issue....on most engines. Angles and the resulting torque is always with-in 10%....or there is something else wrong.
(It also became obvious why Porsche says to never allow the washers to rotate.)
I've never understood the need to prevent the washers rotating when the bolts are being angle torqued.
Torque to a specific ft lbs yes. Some of the torque applied to the bolt head gets "lost" due to friction in the threads and between underside of the bolt head and the washer or between the washer and cylinder head which presumably is different. And is why you shouldn't lubricate bolts that are specified as torque dry.
Angle torque by 90 degrees say and the bolt shank immediately under the bolt head rotates 90 degrees. This applies whether the washer rotates or not. I've never understood where the washer comes into it.
1. I had a few used bolts snap off when tightened. This concerned me greatly, as in the late '70's Porsche changed the head studs on the 911's to unpained/coated Dilivar. These things broke very frequently. If you tried to re-use them in an overhaul, you could sometimes walk away from the engine after torquing the heads and hear the studs shear.
2. When tightening 928 heads with old bolts (and sometimes with studs), I noticed quite a bit of difference between the effort to angle torque different used bolts/studs.
3. So, I bought a torque wrench that measured both angles and foot pounds.
When set to an angle, once it reaches that angle, this tool automatically tells the user (as soon as you remove the pressure) how many ft.lbs. it took to achieve that angle.
Once I could see that data, it was pretty simple to logic out that there was something radically wrong. (50% variance was common.)
Buying new head bolts solved this issue....on most engines. Angles and the resulting torque is always with-in 10%....or there is something else wrong.
(It also became obvious why Porsche says to never allow the washers to rotate.)
Interesting response- point 1 is precisely what I might have expected to hear.
If a used bolt experiences embrittlement I would expect the stress to rise with a steeper gradient on the stress strain curve- thus if one then rotates the bolt to the Porsche specified position it is in effect over rotated in a weakened condition so tensile failure would be no surprise at all.
Point 2 is the give away - I note that you did not comment on whether a "stock bolt" or the "degraded bolt" put up the most resistance.
Regarding point 3 it would be of interest to me if you can advise what torque numbers you typically saw with "degraded bolts" and those bolts that performed "as expected".
In reality there are two ways the bolts could be degraded- one is in the forming process and the other due to process exposure during service. Not long after I graduated there was a step change of thinking in the oil patch regarding the impact of hydrogen in high tensile steels. This came about after a major explosion and fire in a Texas oil refinery where the dished end of a large process vessel literally blew apart during normal service - as I recall this happened around 1982. After that event there was suddenly a lot more focus on material specification and quality control measures. The root cause of the problem was Hydrogen Induced Cracking [HIC]. Suddenly there was a lot more focus on known similar issues such as SSC [sulphide stress cracking], amine stress cracking & caustic embrittlement. If we had to modify piping that had been in service with exposure to hydrogen the metal had to be heated to over 200C for 30 minutes or so to expunge the hydrogen prior to working the metal- failure to do so would cause cracking in and around any weld areas and particularly so in the HAZ. Ultimately these problems led to a new ASTM specification to cover high tensile fasteners that was introduced [as I recall] around 1994- i.e. as the last 928's were being built. This led me to wonder whether the 928 head bolts are up to scratch - maybe bolt specs have been updated since then?
If there was a fundamental problem with what Porsche originally supplied then bolts would have been going twang left right and centre and as I am aware that is just not the case. As you may recall my motor is from my late 90S4. Back in 2005 after I lost my vehicle in a big smash, We refreshed the motor prior to installing it into the GTS chassis. There were no signs of corrosion on the heads or gaskets and everything in the crank/rods area looked fine so was not disturbed at all. After fitting two new inlet valves to replace the bent ones on No7 cylinder, it was time to mount the heads. At the time I asked the agents whether we should replace the head bolts nd they opined it was perfectly OK to re-use them. 17 years later they are still holding up so presumably a sound decision.
The above begs the question if you see such variance in torque values when trying to re-use bolts why is this? It cannot be because the original supply was defective so the degradation has to be because of some exposure but what? The only thing that I can think of might be connected to the problem I have opined about with respect to cylinder head corrosion. The evil brew that forms between the gasket and the heads that attacks both the heads and the gasket material could conceivably be liberating free hydrogen. The trouble with hydrogen is that the mol weight is 2 and the stuff can migrate through steel yet alone gasketed joints that are under attack. I thus suspect that to some random extent, if you see the heads being attacked there may well be a causal link between this phenomena and the bolts you see degraded. In your post I responded to what caught my eye was your comment about how bolts with a "changed appearance" are suspect. I have no idea what the bolts looked like when originally installed but your observation suggests that some form of corrosion, however superficially mild, may have taken place and if so that may well be the reason that such bolts will not perform as expected.
So- what do we conclude from this? Bolts can be reused if they retain their original properties. However if there is an intent to do so, then some form of tensile testing is required to verify such is feasible. If you have some performance data, maybe we can agree a suitable test value that should be attained if for example we undo the bolts and then before removing the heads we torque to spec and measure the resulting values. Given each head has 10 bolts and new bolts are now around $35 a pop or $700 a set there is quite some financial incentive. On the other hand one does not want to risk paying someone like yourself to pull the motor, rebuild it, reinstall it and then find out the thing is leaking and then the entire process has to be repeated as per Mr NamasGT's experience.
In my spare parts bin I have a set of GTS head bolts that covered about 100k km before the motor TBF'd. The original heads had suffered corrosion damage prior to the TBF event- they look black in outward appearance terms. I am now thinking they may be a waste of space!
Regarding the washers and rotation, the only logic I could figure was that the initial torque setting is based on the frictional resistance coefficient between the washer and the bolt. If the washer is sliding over the surface of the head, maybe the starting point for rotation in effect becomes corrupted and the end point is false. Trouble with torque values is they are inferential and can be way off depending on frictional resistance. The only fool proof way to torque a bolt is to mechanically stretch the bolt, and then lock the nut in that position. This is what happens on many critical joints these days but not possible with the fixed head bolts used in the majority of 928's.
I've never understood the need to prevent the washers rotating when the bolts are being angle torqued.
Torque to a specific ft lbs yes. Some of the torque applied to the bolt head gets "lost" due to friction in the threads and between underside of the bolt head and the washer or between the washer and cylinder head which presumably is different. And is why you shouldn't lubricate bolts that are specified as torque dry.
Angle torque by 90 degrees say and the bolt shank immediately under the bolt head rotates 90 degrees. This applies whether the washer rotates or not. I've never understood where the washer comes into it.
It is confusing, to me, also.
You'd logic that when angle torquing, 90 degrees is 90 degrees, regardless of what the washer does.
However, experience tells me that when the washers do slip, the torque value drops...significantly.
And a reduction in torque value has to mean (to me) a reduction in stretch.
But beyond what I personally understand:
When Porsche specifically makes a notation about a certain procedure and writes a caution to not allow something to occur....
I figure they must know more about the subject than I do.
Interesting response- point 1 is precisely what I might have expected to hear.
If a used bolt experiences embrittlement I would expect the stress to rise with a steeper gradient on the stress strain curve- thus if one then rotates the bolt to the Porsche specified position it is in effect over rotated in a weakened condition so tensile failure would be no surprise at all.
Point 2 is the give away - I note that you did not comment on whether a "stock bolt" or the "degraded bolt" put up the most resistance.
Regarding point 3 it would be of interest to me if you can advise what torque numbers you typically saw with "degraded bolts" and those bolts that performed "as expected".
In reality there are two ways the bolts could be degraded- one is in the forming process and the other due to process exposure during service. Not long after I graduated there was a step change of thinking in the oil patch regarding the impact of hydrogen in high tensile steels. This came about after a major explosion and fire in a Texas oil refinery where the dished end of a large process vessel literally blew apart during normal service - as I recall this happened around 1982. After that event there was suddenly a lot more focus on material specification and quality control measures. The root cause of the problem was Hydrogen Induced Cracking [HIC]. Suddenly there was a lot more focus on known similar issues such as SSC [sulphide stress cracking], amine stress cracking & caustic embrittlement. If we had to modify piping that had been in service with exposure to hydrogen the metal had to be heated to over 200C for 30 minutes or so to expunge the hydrogen prior to working the metal- failure to do so would cause cracking in and around any weld areas and particularly so in the HAZ. Ultimately these problems led to a new ASTM specification to cover high tensile fasteners that was introduced [as I recall] around 1994- i.e. as the last 928's were being built. This led me to wonder whether the 928 head bolts are up to scratch - maybe bolt specs have been updated since then?
If there was a fundamental problem with what Porsche originally supplied then bolts would have been going twang left right and centre and as I am aware that is just not the case. As you may recall my motor is from my late 90S4. Back in 2005 after I lost my vehicle in a big smash, We refreshed the motor prior to installing it into the GTS chassis. There were no signs of corrosion on the heads or gaskets and everything in the crank/rods area looked fine so was not disturbed at all. After fitting two new inlet valves to replace the bent ones on No7 cylinder, it was time to mount the heads. At the time I asked the agents whether we should replace the head bolts nd they opined it was perfectly OK to re-use them. 17 years later they are still holding up so presumably a sound decision.
The above begs the question if you see such variance in torque values when trying to re-use bolts why is this? It cannot be because the original supply was defective so the degradation has to be because of some exposure but what? The only thing that I can think of might be connected to the problem I have opined about with respect to cylinder head corrosion. The evil brew that forms between the gasket and the heads that attacks both the heads and the gasket material could conceivably be liberating free hydrogen. The trouble with hydrogen is that the mol weight is 2 and the stuff can migrate through steel yet alone gasketed joints that are under attack. I thus suspect that to some random extent, if you see the heads being attacked there may well be a causal link between this phenomena and the bolts you see degraded. In your post I responded to what caught my eye was your comment about how bolts with a "changed appearance" are suspect. I have no idea what the bolts looked like when originally installed but your observation suggests that some form of corrosion, however superficially mild, may have taken place and if so that may well be the reason that such bolts will not perform as expected.
So- what do we conclude from this? Bolts can be reused if they retain their original properties. However if there is an intent to do so, then some form of tensile testing is required to verify such is feasible. If you have some performance data, maybe we can agree a suitable test value that should be attained if for example we undo the bolts and then before removing the heads we torque to spec and measure the resulting values. Given each head has 10 bolts and new bolts are now around $35 a pop or $700 a set there is quite some financial incentive. On the other hand one does not want to risk paying someone like yourself to pull the motor, rebuild it, reinstall it and then find out the thing is leaking and then the entire process has to be repeated as per Mr NamasGT's experience.
In my spare parts bin I have a set of GTS head bolts that covered about 100k km before the motor TBF'd. The original heads had suffered corrosion damage prior to the TBF event- they look black in outward appearance terms. I am now thinking they may be a waste of space!
Regarding the washers and rotation, the only logic I could figure was that the initial torque setting is based on the frictional resistance coefficient between the washer and the bolt. If the washer is sliding over the surface of the head, maybe the starting point for rotation in effect becomes corrupted and the end point is false. Trouble with torque values is they are inferential and can be way off depending on frictional resistance. The only fool proof way to torque a bolt is to mechanically stretch the bolt, and then lock the nut in that position. This is what happens on many critical joints these days but not possible with the fixed head bolts used in the majority of 928's.
Fred:
Here's a picture of the head bolts out of one of the GT engines which Kyle took apart, recently.
I think this picture might tell you more than I could ever tell....all of those bolts started out that nice golden color.
Besides the obvious color change, note the rust stain on several of the bolts, where coolant was obviously getting past the silicone bead, on the head gasket.
I've got a box of bolts like this, which must weigh a couple of hundred pounds.
I saved them for when the inevitable occurs and Porsche no longer has new bolts and I am forced to "select/find" decent used bolts.
If you figure out a way to recondition them, I'm all ears. Head bolts from '91 GT engine with terrible head gaskets and large amounts of aluminum deterioration. Head bolts from '91 GT engine with terribly deteriorated head gaskets...note the rust stain on the bolt just right of center.
Here's a picture of the head bolts out of one of the GT engines which Kyle took apart, recently.
I think this picture might tell you more than I could ever tell....all of those bolts started out that nice golden color.
Besides the obvious color change, note the rust stain on several of the bolts, where coolant was obviously getting past the silicone bead, on the head gasket.
I've got a box of bolts like this, which must weigh a couple of hundred pounds.
I saved them for when the inevitable occurs and Porsche no longer has new bolts and I am forced to "select/find" decent used bolts.
If you figure out a way to recondition them, I'm all ears.
.
Greg,
Thanks for posting- very illuminating- to me at least!
The message to the OP is very clear- use new bolts unless those removed look like new- most unlikely!
Rather than clutter this thread I will start a new thread covering cylinder heads and corrosion as I perceive "interesting scope" for further discussion/learning.
Update: Heads are off! Took a bit longer than I thought, but they are off and we can see what I am dealing with. Thanks for all the hints and tips so far, I wouldn't have managed without it.
Some photos:
Left hand side head.
I note that on three combustion chambers the intake valves are clean, and on the forth they are black, with carbon on them. Any ideas why?
Right hand side head
Here all the inlet valves are clean.
Individual combustion chambers - with the remains of the head gasket in place.
#1
#2
#3
#4
#5
#6
#7
#8
Block Left hand bank
Individual bores / pistons
#1
#2
#3
#4
Right hand bank
Individual bore / pistons
#5 - With pieces of the gasket that stayed behind.
#6
#7
#8
Gaskets- or what is left of them
#1
#2
#3
#4
#5
#6
#7
#8
As I originally started this job because my cooling system got pressurized and the coolant escaped via the overflow in the reservoir - does these look like combustion chambers / pistons that was exposed to coolant while under pressure?
It is hard to tell with the gaskets in the state they are in, but it doesn't look as if there was blow by across the round metal rings.
On another note, I caught worn cam gears and a leaking tensioner. So that is good.
08-18-2021, 10:23 PM
Took a bit longer than I thought, but they are off and we can see what I am dealing with. Thanks for all the hints and tips so far, I wouldn't have managed without it.
