2005 V6 valvetrain... wtf?
- Thread starter subaruspy
- Start date
-
Sponsors (?)
I think you're referring to the threaded studs/nuts on the exhaust manifold flanges where the H-pipe is secured.
Manifold stud no longer an issue; got that sucka out.
Now that we've wrestled all the new chains and guides and tensioners into place, we're just about to do the final torquing and sew it up. But I have a question about bolts.
The bolts at either end of the jackshaft are spec'ed as torque-to-yield, one-time use, so we've ordered a pair of replacements. I get that, since timing in this stupid thing is completely reliant on their clamping force.
However, the harmonic balancer (crankshaft) bolt is spec'ed one-time use as well, and that doesn't make any sense, since the crank sprocket is the only one of the lot that has a key and thus doesn't rely on the bolt's clamping force to stay in time. So I'm planning not to replace it.
Anyone disagree?
Now that we've wrestled all the new chains and guides and tensioners into place, we're just about to do the final torquing and sew it up. But I have a question about bolts.
The bolts at either end of the jackshaft are spec'ed as torque-to-yield, one-time use, so we've ordered a pair of replacements. I get that, since timing in this stupid thing is completely reliant on their clamping force.
However, the harmonic balancer (crankshaft) bolt is spec'ed one-time use as well, and that doesn't make any sense, since the crank sprocket is the only one of the lot that has a key and thus doesn't rely on the bolt's clamping force to stay in time. So I'm planning not to replace it.
Anyone disagree?
I would replace it if the manufacturer says it is a one time use item. This is something I would not want to second guess and see a failure over. A torque to yield bolt is stretched during the first use. This compromises its integrity for subsequent uses. Hence the reason they are only used one time. Torquing it a second time stretches it even further and weakens the bolt even more at the stretch point. It looks like the price for this bolt runs from $3 to $8 which is chump change considering all the money you have spent already. I wouldn't let such an inexpensive part jeopardize all the time, effort and money you have put into this endeavor.
I do agree with your logic, but am having a hard time seeing why it matters in the case of the crank bolt, since it isn't reliant on tensile characteristics the way the other ones are. And yes, it may be something like a $5 bolt - from Rock or similar - but I'm not within the continental US and buying it will take at least a week, and we're on a very tight schedule for finishing this thing. Or cost $45 from the dealer, as the front jackshaft bolt does (ours comes in tomorrow). So if we go to pick it up and a replacement crank bolt is five bucks and in stock, sure, I'll get it. Otherwise I'll be doing the calculus as to whether it actually matters.
Its your car and your risk. Over the years I have seen people believe they can reuse certain parts without issues only to be sorry down the road. Sometimes it made no difference and other times I have seen rebuilt engines destroyed from a failed used part that should have been replaced. For me, incurring a small cost to reduce a potential major risk is worth it. You can order the bolt, put the engine together with the used bolt and then replace it when the new bolt arrives. I think torquing down a TTY bolt a second time is fraught with potential issues. Usually they are torqued to a specific ft-lb and then turned a certain number of degrees. Doing this with a used bolt is the same as turning a new bolt twice the number of degrees of rotation. The more a bolt is stretched the less reliable it becomes. Just torquing a used bolt to the initial spec might not be possible.
In the end it is your choice. You asked for dissenting opinions and I gave you one.
In the end it is your choice. You asked for dissenting opinions and I gave you one.
- Mar 7, 2002
- 9,432
- 5,380
- 224
Ford uses TTY bolts everywhere that torque matters these days (as does BMW and others). It's not a matter of clamping force in this case, it's a matter of bolt stretch.
As I said, I agree with the generalization, but reserve my right (as an engineer) to question cases in which that rule may not apply. That's why I was wondering about the crank bolt. And axial elongation (stretch) and clamping force are just two expressions of the same thing. But it's an academic argument; when we got to the dealer for the other stuff, it was a five-buck bolt, so we got one.
This did not apply to the broken exhaust stud, which they want $85 for.
This did not apply to the broken exhaust stud, which they want $85 for.
I have a B.S. in engineering but I don't design engines for a living. Therefore, I default to the specs the engineers that do design engines for a living provide us. I have studied mechanics of materials enough to know some things about metal fatigue and what stretching bolts does to their strength. There are very good reasons why TTY bolts are not reused. The bolt in queation is used on a crank pulley that sees high heat, massive forces and high RPM rotations. What happens if this bolt fails when the engine is turning 6k RPM? I think it is worth less than $10 to not find out.
As I said, I bought the bolt (I'm not, after all, an idiot), but I do like running a good debate to ground.
You understand what I'm talking about in terms of the material characteristics. But if you stop and think about it for a minute, you'll realize that the vibration damper bolt out at the front of the crank doesn't actually run very hot - all the serious heat is out at the exhaust manifolds (once this thing is back together, I'm going to see what the actual operating temperature is at that point, just out of curiosity). Nor is it subject to "massive" forces. As I indicated previously, it's keyed to the crankshaft, so that takes care of the radial load, which is light anyway - the few devices that the belt is spinning. And there's no axial load to speak of, just the force needed to keep the pulley clamped in place. So that's why I'm saying that it sounds like this bolt is way overspec'ed.
For me, the main problem is I wouldn't know how compromised the strength of a reused TTY bolt would be. The initial torquing sequence is meant to stretch the bolt to achieve proper tightening. Torquing it a second time using the same procedure at a minimum doubles the stretch and might stretch it even more since the cross sectional area of the stretched part of the bolt is less than it should be. It might not be an issue to reuse this bolt but it is a gamble to do so.
I have been an engineer for a long time. Over my career I have had to collaborate with other engineering disciplines. There is so much specific knowledge that is needed to work in each one and I found that it is impossible to know this specific knowledge unless you are immersed in a particular discipline. What we learn in college regarding undergraduate engineering is very general knowledge. What we learn working in a given discipline is far more detailed and complicated. Working with other experts in other disciplines is humbling as to how much you don't know outside your own area of expertise. This is why I don't second guess an expert in another discipline where I don't have direct, personal knowledge regarding the intricacies of doing their type of engineering.
We may be of about the same vintage (in practice for ~40 years), and what you say about the discipline is right on the mark. I too have been very fortunate to have done a lot of interdisciplinary work, and to be privileged to have been able to add to my circle of friends a steady stream of collaborators orders of magnitude smarter than me - and who still impressed me with their own humility. Sure, there have been a few jerks along the way who were too full of themselves, but over time you develop a keen eye for steering clear of them. I live by the mantra that if you're stupid, you need to surround yourself with smart people, and if you're smart, you need to surround yourself with smart people who disagree with you.
But... you left out one of the most important parts: That over time you develop a rock-solid gut instinct for problems. So that's all that's at work here. With more information on the material specifics we could definitively solve this question (though it would take more than $5 worth of time and effort to do so, which is why I bought the bolt). But much, much more often than not, when faced with a problem like this, guys of our level of experience can look at its overall parameters and say "Yeah, I've got a pretty good idea what's at work here". That's all I'm doing - broadly looking at the problem and making the judgement call that if I were to reuse the old bolt I wouldn't be any less comfortable with its reliability than with the new one.
But... you left out one of the most important parts: That over time you develop a rock-solid gut instinct for problems. So that's all that's at work here. With more information on the material specifics we could definitively solve this question (though it would take more than $5 worth of time and effort to do so, which is why I bought the bolt). But much, much more often than not, when faced with a problem like this, guys of our level of experience can look at its overall parameters and say "Yeah, I've got a pretty good idea what's at work here". That's all I'm doing - broadly looking at the problem and making the judgement call that if I were to reuse the old bolt I wouldn't be any less comfortable with its reliability than with the new one.
manicmechanic007
5 Year Member
That's good bedside manor MustangIIMatt
Terrible nasty job
And those Ford engineers told us techs they were going to put us out of a job
Not likely
Terrible nasty job
And those Ford engineers told us techs they were going to put us out of a job
Not likely
manicmechanic007
5 Year Member
Wondering subaruspy if you have had the pleasure of replacing headgaskets on a turbo subaru?
If you can do them you can possibly do this
If you can do them you can possibly do this
I've been pretty far into Subarus for about a decade now, and have done lots of head gaskets on EJ22s and EJ25s (both SOHC and DOHC), both in and out of the vehicle. Really isn't any sweat, though the torquing procedure (esp. the final 45 degree tightenings in later engines) is a PITA. I'll be doing a couple of EZ30s this summer. I haven't actually done any turbos myself, because I've been careful to follow the best advice out there, which is "Friends don't let friends buy 2.5 litre turbos". Those engines are nothing but trouble; a close friend of mine (retired mechanical engineer) has been at war with a pair of them for a couple of years now. But the procedure isn't very different, modulo the extra turbo plumbing.
The more relevant comparison is in doing the timing, which - with all keyed sprockets and shafts - is trivial compared to this nightmare.
The more relevant comparison is in doing the timing, which - with all keyed sprockets and shafts - is trivial compared to this nightmare.
manicmechanic007
5 Year Member
This Ford 4.0 isn't that bad
You will have parts strewn from hell to breakfast
Give yourself a cigar when done
Getting pleasure now with a Mercedes balance shaft job
4matic took me a solid week to get the trans out
You will have parts strewn from hell to breakfast
Give yourself a cigar when done
Getting pleasure now with a Mercedes balance shaft job
4matic took me a solid week to get the trans out
manicmechanic007
5 Year Member
I just used that Subaru as a reference to see if you were a tech or not
I agree they are easy and I agree about the hard part
The last step with those head bolts
Makes me wonder if they think 280 ft lbs will help the gasket failure they got going
See where they are giving up on turbos and my Subaru driving lawyer buddy is pissed
I agree they are easy and I agree about the hard part
The last step with those head bolts
Makes me wonder if they think 280 ft lbs will help the gasket failure they got going
See where they are giving up on turbos and my Subaru driving lawyer buddy is pissed
Well, that's not to say that all Subaru turbos are NFG - it's just that the 2.5GT is a bad combination. The turbo 2.0 litre has a great rep.
But back to today's problem at hand: Now that all the new timing bits are in, we just have to torque all these sprockets - but I don't have a good grasp of how. It seems obvious that the starting point is both ends of the jackshaft, then the timing cover goes on, and finally the cam sprockets. I do have the Taiwanese knockoff tool kit.
Haynes says that the front sprockets get 33 ft-lb + 90 degrees, and the back sprocket gets 15 ft-lb + 90 degrees. BUT...
How do you do this if you can't somehow lock the shaft itself? If I'm torquing the front bolt, how do I know the shaft isn't spinning and tightening the rear bolt, or vice versa?
But back to today's problem at hand: Now that all the new timing bits are in, we just have to torque all these sprockets - but I don't have a good grasp of how. It seems obvious that the starting point is both ends of the jackshaft, then the timing cover goes on, and finally the cam sprockets. I do have the Taiwanese knockoff tool kit.
Haynes says that the front sprockets get 33 ft-lb + 90 degrees, and the back sprocket gets 15 ft-lb + 90 degrees. BUT...
How do you do this if you can't somehow lock the shaft itself? If I'm torquing the front bolt, how do I know the shaft isn't spinning and tightening the rear bolt, or vice versa?
- Mar 7, 2002
- 9,432
- 5,380
- 224
If you have the right tool and have it set up correctly, the camshaft can't turn.
View: https://www.youtube.com/watch?v=WJax1KPtRB8&ab_channel=CloyesGear%26Products%2CInc
.
Similar threads
- Locked
