VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: Dr. Diesel on August 10, 2004, 03:58:42 am
-
I called raceware for head stud torque specs after having pulled the head off for a gasket change. I wanted to know what the specs were for installation without the moly based assembly lube. He told me 50 ft.lbs. in three stages using 20w50 engine oil. That seemed quite low, so I mentioned that my engine builder told me 70#'s with the correct moly lube. (he'd done only the first two stages when I picked up the engine.) The raceware dude, Randy, just about laid an egg when he heard that number. He said the studs were probably stretched and needed replacement. I called the builder again and he couldn't have disagreed more. He compared them to ARP's products and said a grade 12 1/2" stud (close enough for this example) should be torqued to at least 70#'s closer to 130 with engine oil rather than moly assy. lube. We postulated that despite Randy's claim that raceware is better than ARP, perhaps he was using a lower grade stud. I had to wait for the weekend to pass before I could contact raceware again. Randy didn't seem to think that fastener material higher than grade 8 even existed. He didn't know what grade his studs were, and could only quote tensile strengths. Based on his 190,000psi claim, that's roughly a grade 12 stud. Torquing them to 50 #'s with engine oil would surely have resulted in a blown gasket.
Moral of the story, should you buy raceware, beware of your torque specs!
-
Dr. D - you've got to consider the thread pitch when determining how much torque to apply. A steeper (IE: courser) thread pitch will require more torque to develop the same amount of fastener clamp-load.
Why are you (or your engine builder) second-guessing the manufacturer's recommendation? I would recommend using the 50ft-lb torque specs (with a beam wrench not a clicker and also lubicated with non-synthetic oil), as recommended by Randy Hubbard, who seems to be very competent to me by the way and has always provided knowledgeable information and support to me whenever I have ever requested it also. I have never had one iota of problems with the racewares (and believe they have saved my head from warping on an overheat occasion or two!) using the 50ft-lb torque spec, as recommended by the manufacturer.
Jake
-
I'll dig out my mechanics of material/strenghts of MAT - and get back here.
-
Jake, this isn't a Randy trashing. I never saw the instructions, and they'd been pitched by the time I picked up my engine. For me, it was a toss up as to who to trust. A guy I don't know who couldn't even provide me with the grade of material he uses, or my engine builder who has been involved in almost every facet of combustion engine technology from design to build, rebuild and modify in his time. If he'd simply said "I don't know" then I'd have gone with what Randy said. My engine builder insisted (and confirmed with ARP 'cuz Raceware had already closed for the day) that a 190,000 psi stud of that diameter is at least a grade 9, more likely a grade 12. (Randy said guaranteed minimum 190,000, but on average closer to 220,000) In that case, the torque spec should be as mentioned earlier.
I didn't measure the thread pitch on these studs, but they looked like the same fine thread pitch of the gas engine ARP studs I've used in the past.
You said you used the same 50# torque spec on your studs, perhaps Randy's info is wrong (he actually said his studs were grade 8 because grades higher than that don't exist!) and we could actually be getting so much more clamping power out of these sets. Really, the factory fastener is tightened more than 50#. Why would a stronger fastener use less? It simply doesn't make sense. That's why I chose to go with the rebuilder's recommendation. I've installed the head twice at those torque specs with no issues. Thoughts?
-
Jake, this isn't a Randy trashing. I never saw the instructions, and they'd been pitched by the time I picked up my engine. For me, it was a toss up as to who to trust. A guy I don't know who couldn't even provide me with the grade of material he uses,
Dr. D - same thing goes for other Aerospace quality hardware. Usually they use a military grade, or just give direct quote and description of the specification (IE: tensile strength, "suitable for application x", etc.) Would you want the Society of Automotive engineers, who specialize in cost-effective mass-production of automobiles, having a part in specifying what parts to put on an aeroplane? On a multi-million $ F1 racing vehicle consisting of very expensive, lightweight but highly stressed components? It's not the appropriate specification to ask for, IMO. If aerospace grading (NAS, MIL-spec, etc) is good enough for the space shuttle and Formula 1, etc, it's good enough for me! Just my opinon anyway. SAE grading are not reliable and cannot be relied on anyway, I believe they are manufacturing guidelines, not guaranteed tensile strengths. Aerospace grades are always more reliable than SAE grades from what I hear. I am not an authority on the subject, but if you wanted to learn more there are a couple books on the subject oriented at serious racecar engineering... and there is primarily a focus on fasteners, fittings, high strength to weight ratio materials, etc. "Engineer to Win" by caroll Smith (http://www.amazon.com/exec/obidos/tg/detail/-/0879381868/102-1357718-6528149?v=glance) comes to mind. I don't have this book myself but I would say that is authoritative, and from what I hear, IIRC, Caroll Smith is quite the basher of using SAE-graded fasteners on racecars.
or my engine builder who has been involved in almost every facet of combustion engine technology from design to build, rebuild and modify in his time. If he'd simply said "I don't know" then I'd have gone with what Randy said. My engine builder insisted (and confirmed with ARP 'cuz Raceware had already closed for the day) that a 190,000 psi stud of that diameter is at least a grade 9, more likely a grade 12. (Randy said guaranteed minimum 190,000, but on average closer to 220,000) In that case, the torque spec should be as mentioned earlier.
As I said before, thread pitch must be considered. You can't assume they're the same, because the raceware head studs might have finer thread pitch than ARP, therefore require less torque to make the same clamp load. The thread pitch of the upper part of the raceware studs, which the nuts fasten on to, is certainly finer than the threads at the bottom which screw into the block (equivalent to the stock head bolts.)
I didn't measure the thread pitch on these studs, but they looked like the same fine thread pitch of the gas engine ARP studs I've used in the past.
You said you used the same 50# torque spec on your studs, perhaps Randy's info is wrong (he actually said his studs were grade 8 because grades higher than that don't exist!)
I haven't heard of any SAE grading high than 8 being used either actually... usually like I said before, you go to NAS (Navy-Aerospace) specification bolt, or other specification more suitable for a highly-stressed component than SAE grading when talking aerospace quality hardware.
and we could actually be getting so much more clamping power out of these sets. Really, the factory fastener is tightened more than 50#. Why would a stronger fastener use less? It simply doesn't make sense.
I would say primarily it's due to the finer thread pitch of the raceware studs/nuts vs the course threads of the stock head bolts.
That's why I chose to go with the rebuilder's recommendation. I've installed the head twice at those torque specs with no issues. Thoughts?
Different metal has different yield characteristics. Some yield abruptly, IE: shatter when they exceed their yield strength. This will be quite obvious when it happens... Other metals (including I think the high strength chro-moly steel used in these kind of bolts) will deform gradually and plastically, so yielding may not be obvious. An other example of this is the stock strength head bolts - they yield gradually (can we tell one that has already stretched vs a new one? I don't know - would be interesting to see how significantly the lengths actually differ, of used vs new factory stretch head bolts.) There could be some stretching along the length of the threaded part for example, caused by a 40% (considerable) overtorque. Assuming those specs Randy gives are close to the yield point, as I would expect they are, and as they should be. But I don't know. 50ft-lbs as recommended by Raceware, with non-synthetic oil, and with a beam-style torque wrench not a less-accurate "clicker", has worked well for me and everyone else I know of who has run them in VW Diesels.
Raceware makes it pretty obvious in their instructions/literature they send out with their vw diesel head studs by the way, not to use factory torque specifications but to use theirs for their bolts. Along with the added requirements of not using synthetic oil to lubricate the threads (but rather non-synthetic) and also not using a clicker torque wrench but an accurately calibrated beam-style. They are really quite fussy about proper torquing! It's too bad you didn't get that information when you got your fasteners and/or engine. Sorry to hear about this and good luck... you might ask Randy what he would advise, besides buying new ones.
-
You also wouldn't have to torque them so high if the threads were more slippery. Co-efficient of friction is less so it takes less torque on the nut to get the same downward force.
Raceware coats the fine threads with a special sauce that makes them more slippery ...this is in addition to the 20-50 you add.
the factory fastener is tightened more than 50#. Why would a stronger fastener use less
The threads in the block are not as fine as the threads on the top of the head studs ...thread pitch.
-
All valid points. I needed the grade of these studs to do a comparison, to TRY to make two, even three opinions match. It was difficult to decide what to do in this situation. I'm going to get to the bottom of this once and for all and measure the relaxed lengths of these studs and give Randy a call.
-
Well, after pulling the engine apart AGAIN, I had a very close look at the studs. They threaded out of the block easily, and the nuts threaded down the studs easily. Randy said if the studs were stretched, it'd be in the threaded area, indicated by a difficult time threading the nuts, if not by obvious visual clues. Nothing. I measured their lengths and they're still in spec. Then I compared them to a set of ARP gasser studs. Same diameter, same thread pitch, same 190,000psi tensile strength. The ARP hardware did have it's instructions still, and they said 70 #'s with moly lube. Randy's faxing me the installation instructions to replace the ones that got tossed. I'll see them in about an hour. So now I'm still not convinced. Seems to me that such an gross overtorque as I've twice done already (4 times, if you include the after-up-to-temp-and-cool-retorque) there'd be some sort of indication of damage. So I've got two different ARP reps, some other fastener company (that I didn't catch the name of--engine builder's supplier) and my engine builder (i'm going to call him MEB from now on to save my fingers) all saying one thing, which I feel makes sense, and Randy (the manufacturer, who should be right) saying another completely different thing, which based on all the facts in front of me, doesn't make sense.
K, just this moment I received my faxed installation instructions from Raceware. I see where you get all your info from, Jake! I can say that I'll be buying a beam type torque wrench tomorrow.
The nugget that tipped the scales
Quote:
"Most RACEWARE Head Stud Kits are supplied with Aircraft style 12 point nuts that have an exclusive anti-friction coating that lowers friction and improves tightening accuracy, a common problem with other fasteners."
Well, there it is. I guess MEB owes me a new stud set. Fancy how things get frocked up when asumptions are made, and instructions not read. And, now there's another weekend to wait through before I can order another stud set, which means I'll miss Dave's drag weekend. CRAP! :evil:
-
quick question:
At what point are the factory bolts no longer good enough and one must use studs? Also, do I read you correctly, these are the same studs as a 1.8 8v gasser?
BTW, if you're the guy with the mad Mk2 red TD Jetta at the Hershey centre auto-x on May 25th, I have a video of your run. lmk if you want it.
thanks
-
quick question:
At what point are the factory bolts no longer good enough and one must use studs? Also, do I read you correctly, these are the same studs as a 1.8 8v gasser?
Nope, gassers are shorter. Not sure at what point studs are required. My old engine sometimes saw 30 psi on stock bolts. Never blew a head gasket.
BTW, if you're the guy with the mad Mk2 red TD Jetta at the Hershey centre auto-x on May 25th, I have a video of your run. lmk if you want it.
thanks
That's me, and I'd love it!
Thanks!
-
I want it too !!!!!!!!!
-
cool, I'll upload it and post a link.
back to the topic, I've heard the 1.6 likes to blow its head gasket if it sees more than 15#'s. I take it there's more than one side to the story? Are you using 1.9L gaskets? I'm also guessing you're using studs because you end up taking your head off often enough?
I'm trying to learn from the side lines, getting ready for a 1.6td build-up.
-
I'm using OE gaskets. Trust me, if I could possibly avoid it, I'd far rather keep the head on the damn engine and drive the car rather than have it sitting around in pieces, missing autocross races! The studs were used more as a precaution than anything.
-
I actually forgot I have already uploaded the videos a while ago, here's the link:
http://www.vwot.org/~greasemonkey/May%2024%20videos/
There are some pics of your car too, here:
http://tinyurl.com/3ogl8
So would you say OE 1.6-spec parts are good enough for say less than 20#'s boost?
-
One advantage with aftermarket, high-quality studs is that if you overheat the motor, for example say you blow a coolant hose and run it until it gets real real hot. Well in that scenario I think that the extra strength of the head studs really helps keep the head fastened flatly to the block. With OEM weaker stretch bolts, they can give in that scenario (of overheating) and then the head can warp, or "bow". Head studs can be the difference of the engine running again as good as it used to following the overheat, vs the head being warped and there being a head gasket leak problem.
I would use my racewares if they were legal in my racing class. There is another advantage that you can pull the engine apart and put it back together and can re-use the hardware; rather than having to buy a new set of stretch head bolts.
-
This is an intresting topic, that I have read a lot about, but don't know that much about. I was recently in the mall waitng for the wife to buy somthing or other, and I picked up an issue of hot rodder, or somthing like that and in there they had an article on setting "torques for hi- performance engines" and in this article, they said that the only true and correct way to "torque"is by mesuring the stretch with a dial indicater, and then they went into examples of oem head bolts as well as arp headsutds were they torqued them to the "spec" as per instructoins pased on lube or oil or dry, and none of them came even close to what they should have been via the streach numbers, due to the incosistincy in the friction level between the block and the stud. Moral of the story if it isn't set via strech number it isnt set right. This is how it is done in F1, indy, cart, baja, nascar, nhra, ihra, ect... The other thing that I read was from a builder or custom copper head gaskets, in regards to torquing and HP that you make the most HP with the least possible torque that still seals the head. so ???? well I am confused, but I would probabley be inclined to go with the strech version myself :wink:
-
This is an intresting topic, that I have read a lot about, but don't know that much about. I was recently in the mall waitng for the wife to buy somthing or other, and I picked up an issue of hot rodder, or somthing like that and in there they had an article on setting "torques for hi- performance engines" and in this article, they said that the only true and correct way to "torque"is by mesuring the stretch with a dial indicater, and then they went into examples of oem head bolts as well as arp headsutds were they torqued them to the "spec" as per instructoins pased on lube or oil or dry, and none of them came even close to what they should have been via the streach numbers, due to the incosistincy in the friction level between the block and the stud. Moral of the story if it isn't set via strech number it isnt set right. This is how it is done in F1, indy, cart, baja, nascar, nhra, ihra, ect... The other thing that I read was from a builder or custom copper head gaskets, in regards to torquing and HP that you make the most HP with the least possible torque that still seals the head. so ???? well I am confused, but I would probabley be inclined to go with the strech version myself :wink:
Generally speaking, the way I understand the "pros" IE: (F1 engineers) set the torques of their fasteners is they determine the torque at which the fastener yields and torque to a certain percentage, IE: 80-90%. The way they determine this is either by looking up on a table and/or calculations based on size, thread pitc, materials, and lubrication, or they can actually buy extra (they've got enough money, right?) and torque a fastener until it yields, then remove it, replace it with a new one of the same type, and torque it to a little bit less.
I think I understand the train of thought of the guy who said the least amount of torque is best for power, but I think I disagree with his recommendation. He is probably saying that because of more clamp load, there is more strain (movement/distortion) of the head/block assembly, and that a block with cylinders that is strained will have the cylinder-shape bores change into oval-shape bores. The piston will rub unevenly and seal less well on an oval bore and therefore, will make less power when the bores aren't perfectly cylindrical. I think I agree with all that (although I'm not sure how big of a factor it really is.) But undertorquing goes against the other good practice rules with ensuring a good head gasket seal, IMO. Based on what I've read, more bolt load is generally better; and the VW head/block seems plenty stiff. The recommended practice in eliminating the "oval bore" syndrome is rather than reducing bolt load, is to machine the bores with the stresses of the head and head fasteners at full torque simulated. Very good machinists will have fixtures called "torque plates" that bolt onto the engine block, sort of like a "simulated head", but with big holes in them for the boring/honing tool to reach through and machine the bores. They will bring the simulated head fasteners up to full torque before doing machining the final bore/honing operations on the cylinder. Then the perfectly machined cylinders will in theory remain cylindrical when the real head is bolted and torqued up on top of there. Using a torque plate is one of those little machining tricks that makes the difference between an econo-rebuild suitable for street use, vs a high quality blueprinted type of engine rebuild. Some machinists have torque plates and use them for rebuilding VW motors, others don't.
A danger with undertorquing is if the pressure on the cylinder head exceeds the bolt load, the bolts can then see a dynamic loading where they stretch and relax a little bit with each cylinder fire. This can lead to failure of the fasteners, even though they may be installed at a load far under their yield or tensile strength! You might think, there is less chance of failure of the fastener if it's torqued less? Well it sounds weird but it is not necessarily true. Over time small amounts of stretching from dynamic oscillations of an undertorqued bolt can lead to metal fatigue of the fastener material. (Not to mention the head gasket will have a tough time sealing when the surfaces pressing against it are moving!) As a result of this, the general practice is to specify fastener torques that comes as close as possible to the yield strengh of the fastener, assuming the material being fastened is adequately rigid and there is adequate thread engagement, etc.
I think you are right about lubricant effecting torque readings drastically. When I torqued head bolts with only oil lubricant as specified by bentley, it can be felt how much friction there is and the lack of "smoothness" when torquing the bolt because of all the friction. But when I lubricated the threads with moly lube, boy did they torque up smoothly. It would be very difficult to measure the lengths of installed head bolts/studs as they are threaded into blind holes! A bolt that had both ends exposed, that wasn't threaded into a blind hole, might be measurable however. What you could do is measure the length before/after installation of the bolt though, to see if it has permanently stretched at all. If it has permenently stretched, it was torqued to above it's yield strength.
-
DR D - cost of the stud?
I cannot reach my email - to get a message off to the gang!
Thanks! - C
-
i think they're around $145 U.S for the set.
-
After reading this thread, I want a set of raceware. Where do I get them? I couldn't find them on Jack's site. Could be I wasn't looking in the right place.
Thanks in advance.
Tim
-
After reading this thread, I want a set of raceware. Where do I get them? I couldn't find them on Jack's site. Could be I wasn't looking in the right place.
Thanks in advance.
Tim
http://www.raceware-fasteners.com/photo.htm
m alexander
-
Doc:
Just for referrence, here is a complete list of SAE and ASTM fastener grades. As you will see, there is no such animal as "grade 12". While I am tempted to say YEB is blowig smoke up your rear, the truth is that few people ever bother to learn anything about fasteners and live by old wives tales, industry slang, and so on. Even in fastener stores, one will often hear of "grade 10" bolts (that the manufacturer has decorated with more than the usual number of grade-code markings on the head) - which, as I said, don't exist as a standard.
Now, if you (or anyone else) has some later information that SAE has added some new standards, I am all ears (and eyes).
http://www.americanfastener.com/technical/grade_markings_steel.asp
What I found interesting when I searched out this table for you is that the ISO grades shown at the bottom are strangely missing 12.9 (which is closer to what Raceware and ARP studs would be).
To those referring to measuring stretch as a legitimate method of torque measurement: very true - for rod caps. You can also do so by measuring how much the main caps grow (if you were to use studs). However, for a head, you have the little problem of a gasket below that will crush and not allow you to have a "zero referrence" point from which to measure. The fact that it is a blind fastener is not a big deal (since you assume that the other end is not moving at all, so you measure the increase in length with a dial indicator on the free end).
BTW: thanks for this thread. I have been agonizing over the ARP/Raceware issue for some time (building another high-ish HP 1.9). Don't know if I am decided one way or another, but I definitely have a lot more good information upon which to base my decision.
-
that link also left out socket head bolts which are alloy for the most part anyway. I have been working on somthing for Myke_W for about 2 months and haven't had a good enough answer to get back to him, but after reading this I think I will try it on my next turbo. I sell these SPS Unbrako bolts that are in all sorts of industries...I can get them at my cost and offered them to Myke first. But I don't want to give somebody something that doesn't work or work correctly for this application. I haven't heard back from SPS what the torque would be for VW diesels and I don't think I will since it is a small market for them. I need to get my turbo engine bored and put back together before I can tell you it they work or hold up. Here's the link for the some of the stuff I sell.
http://www.spstech.com/business_groups/unbrako.html
-
50ft-lbs as recommended by Raceware, with non-synthetic oil, and with a beam-style torque wrench not a less-accurate "clicker", has worked well for me and everyone else I know of who has run them in VW Diesels.
Raceware makes it pretty obvious in their instructions/literature they send out with their vw diesel head studs by the way, not to use factory torque specifications but to use theirs for their bolts. Along with the added requirements of not using synthetic oil to lubricate the threads (but rather non-synthetic) and also not using a clicker torque wrench but an accurately calibrated beam-style. They are really quite fussy about proper torquing! .
Interesting thread, my question is if the beam-style is better than a "clicker" torque wrench, I wonder why the military doesn't require all torques to be accomplished with a beam-style only. All we use in the Air Force is "clicker" except for the altra light 4 to 20 inch pound torques where we use a beam style. One other thing is you hear that if you use a "clicker" not to double click it but just go with the first and only click, but you see it on national TV on HorsepowerTV putting an engine together and hearing them double click. :?
-
It's back to the same thing: people just don't pay enough attention to fasteners and fastening tools, and "go with the flow" of what is around them.
While bending beam torque wrenches have SOME advantages, reading a wiggling needle on a shaky scale, trying to correct for parallax (since it always reaches value somewhere almost out of sight!) is a real PITA. I have ONLY ONE of 3/8" (MAN I wish I have bought the 1/4" and 1/2" drive when I could - but I was doing only air cooled then, and didn't need them) Repco bending beam torque wrench with a little wedge on it that slides along to allow it to hit a trigger that releases a pin at the pre-set torque. It if audible (barely), visible and tactile (fires against your thumb) and meant for aircraft work. The wedge is very soft, and the trigger point is very hard and sharp. After releasing the pin, a bit more deflection puts a mark on the ground face of the wedge.
As I understood it when I got it (over 30 years ago) workers would engrave their name on the wedge, and the QA/QC crew would collect them at the end of the day. Mark up your wedge, and your work (and you) would be re-doing the day's stuff. Another feature was the drive was removeable and available in calibrated torques - that is they would break if taken beyond their marked value (a great way to protect really expensive stuff). Needless to say, if a mark got you called on the carpet, I imagine a broken drive was a pink slip.
Why do I mention all of this stuff? Because THAT is how fastener tension should be treated.
-
These are what I am going to experiment with.
http://www.spstech.com/aero/products/sde_studs/sde_studs.html
After more and more digging here is a competitor of mine that sells the stuff in just our kind of usage.
http://www.aaa-aircraft.com/pdf/sps_racing_brochure.pdf
-
does anyone have the torque specs for the racewares lying around??? i had the sheet but now i can't find it!!! :(
-
I bought a newly rebuilt engine with Raceware studs. One was missing and one was untorqued. If I relax them all then retorque to Raceware specs should this be good enouogh?
Brian
-
well i dont think you have any other options... i would just do it and hope for the best... except for the missing one. maybe you can order just one?
-
does anyone have the torque specs for the racewares lying around??? i had the sheet but now i can't find it!!! :(
I have the sheet somewhere. I'll dig it out and post the values.
Best I can remember:
20
35
50
lets see how close I come to whats on the sheet.
Actually the final torque is important, and as long as the lower torque steps are more or less evenly spaced, you should be OK.
Heck do 16.67 ftlb stages to 50.
-
well i dont think you have any other options... i would just do it and hope for the best... except for the missing one. maybe you can order just one?
I already ordered the missing one. I installed it and torqued it. I checked all the other ones and have started the engine and driven the vehicle briefly. But maybe I should relax them all and retorque.
-
I have arp studs in my TDI I torque them to 105 ft-lbs.With the metal head gasket you gan actually feel it stop compressing at approx 100 ft-lbs.I just go to 105 to seal the deal :lol:.Any less than 100 and you are asking for possible leakage.
-
I have arp studs in my TDI I torque them to 105 ft-lbs.With the metal head gasket you gan actually feel it stop compressing at approx 100 ft-lbs.I just go to 105 to seal the deal :lol:.Any less than 100 and you are asking for possible leakage.
don't forget about that 'nifty' anti friction coating they put on the racewares though. they should only be torqued to 50 ft/lbs or maybe 60 ft/lbs.