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Engine Specific Info and Questions => IDI Engine => Topic started by: Rabbit79 on February 06, 2011, 02:48:54 am
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After getting my head back from the machine shop I noticed they'd taken out the stud for the timing belt tensioner. I didn't think much about it at the time but now that I'm finally getting around to putting all this back together I can't remember which way the stud goes back in, or if it even matters. Anyone have a head laying around with the tensioner pulley off that they can look at real quick and refresh my memory?
Here's what I've got:
You can see from this picture I've got more thread to one side of the stud than the other.... I don't know for sure if that's how it's supposed to be or not. The only picture I can find of one is in the Haynes manual and it shows it being threaded equal lengths on both ends, with a much larger smooth portion in the middle. This could just be a home-made job that someone put in there at some point in the cars life, although it has worked just fine in the 14 or so years that I've owned the car.
(http://i859.photobucket.com/albums/ab151/08Hes_dead_Jim/Rabbit%20engine%20rebuild/02050005.jpg)
So do I go with option 1:
(http://i859.photobucket.com/albums/ab151/08Hes_dead_Jim/Rabbit%20engine%20rebuild/02050002.jpg)
(http://i859.photobucket.com/albums/ab151/08Hes_dead_Jim/Rabbit%20engine%20rebuild/02050006.jpg)
Or option 2:
(http://i859.photobucket.com/albums/ab151/08Hes_dead_Jim/Rabbit%20engine%20rebuild/02050009.jpg)
(http://i859.photobucket.com/albums/ab151/08Hes_dead_Jim/Rabbit%20engine%20rebuild/02050007.jpg)
Any and all help appreciated
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I do not know the correct (factory) orientation.
I do know (don't ask me how, just take my word for it ;-) that if possible a stud should ALWAYS be installed so that the shoulder of the stud meets the top of the threaded hole before the stud is able to bottom in the hole. If a stud is allowed to bottom in it's hole, it can (or for me, definitely will) either 1)seize and then shear off, requiring me to waste much time extracting it, or 2)push through the thin, aluminum bottom of the threaded hole and penetrate the water jacket in the head, therefore causing me to say really bad words before I go looking for a replacement head.
I hope this helps.
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Mine has the long portion of thread sticking out.
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Mine has the long portion of thread sticking out.
2X.
Another clue is that sometimes when you buy 'em there's blue locktite on the short end.
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Thanks fellas. I kinda thought that's how it went but I wasn't sure so thought I'd ask. Interesting that with all the timing belt changes and other related stuff I've done over the years I never paid one bit of attention to how that stud was in there. I like to tell myself I would have noted the orientation had I taken it out myself... but who knows.
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Much better to reason things out... slow and careful like... especially when the timing belt is involved. :)
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I will forward this to ex-wife # 1 , she thinks she knows something about stud's
I would go with 12.9 grade stud and locktite
GB
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I will forward this to ex-wife # 1 , she thinks she knows something about stud's
To which your reply should be "obviously not..... since you divorced me"
I would go with 12.9 grade stud and locktite
GB
Never heard of 12.9. 10.9 I have heard of though. One thing about this old car that makes me happy is a lot of the bolts are property class 10.9 (roughly equivelant to grade 8 in SAE usage), which means they'll probably all last as long as I do. I don't know for sure what that tensioner stud is, as there are no identifying marks on it, but it's still in good shape. I wonder though if a 10.9 would be overdoing it threading into aluminum? Probably no more than an 8.8 I guess, just thinking out loud.
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I wonder though if a 10.9 would be overdoing it threading into aluminum? Probably no more than an 8.8 I guess, just thinking out loud.
A stronger bolt would allow you to torque it harder in which case the head threads would give first. I'd go for a stronger bolt just so it could hold the side load.
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Torque spec on that 13mm nut is not that much mind you... I think you'll be fine with what you've got. ;)
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Torque spec on that 13mm nut is not that much mind you... I think you'll be fine with what you've got. ;)
Both of my diesels have a 15mm nut.
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Mine has the 15mm nut. 33ft/lbs is what the Bentley says for the nut, but I don't see anything for the stud. Granted I didn't look that hard either. I just went to 29 with blue loctite on the stud, as it felt like it was getting pretty tight and I really don't care to strip the threads out of the head (or crack it either). Hopefully it won't want to come out every time I loosen the tensioner.
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For the stud I think slightly more than finger tight is good.
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How tight are you guys cranking your timing belts? The stock bolt will do just fine for the loads involved. I'd put the short end in the head with a little blue loc-tite mainly so that there would be no possibility of the nut hitting the shoulder if it should project beyond the face of the pulley and then you would be turning the stud in the head and aluminum threads don't like that on a repeated basis.