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Thread: ARP Main stud issues

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    ARP Main stud issues

    I figure the FI guys are the best to ask....

    Motor: S52

    ARP main stud kit: P/N 201-5000

    Threading the studs in by hand, I get them to bottom out in the block. No issues. I put the caps on, then the washers, then the nuts. It's obvious that even after I torque the nuts, I am not going to get complete thread coverage on the nuts. In other words, the stud end will not come all the way up through the nut.

    The studs are 3.758" long. I call ARP and they confirm this is the correct kit and stud length for the US M50/M52/S50/S52 engine. I ask about the S54 kit (p/n 201-5002), and they tell me that kit has studs that are exactly the same as the S52 kit, only the studs are 4" long. That extra length would be exactly what I need to get complete thread coverage on the nut.

    So, what the hell? Am I the only guy to ever bring this up to ARP's attention? Has anyone else had the issue, and if so, what was the solution? Dropping a spacer down in there, to me, does not appear to be an adequate solution (that appears to be what this guy did, after a search on the subject: http://forums.bimmerforums.com/forum...light=arp+main).

    Unless someone in this thread comes up with a magical solution, I think I am just going to use the S54 studs. Leaving the nuts hanging 25% off, to me, is not right. The alternative to this would be to not bottom the studs and torque the nuts with full coverage, but I suspect that's going to lead to inaccurate torque readings.

    Ideas, opinions, experiences?

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    techno550 is offline Senior Member Supporting Vendor
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    backing off the stud would be a solution. Do you have a picture of the stud next to a stock bolt?
    Michael McCoy TRM

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    Its only a solution if you install an insert so the stud can bottom out


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    Thanks for the link. I'm not as comfortable as you are with backing off the stud to get more thread into the nut. It just means I'm getting fewer threads into the block, and I'm concerned about accurate torque readings on a stud that's not bottomed. This isn't going to be a turbo motor but it is a race motor that's going to top out around 7400 RPM and will live 90% of it's life at full throttle.

    I don't have a pic of the studs next to the factory bolts, but I did compare them last night and the "incorrect" studs I have are longer than the factory bolt - which means the factory bolt (obviously) does not bottom in the hole...makes sense, since it has a head, not a nut.

    I'm interested to see if anyone's used the S54 studs, since they're 1/4" longer. ARP says the threads that go into the block are identical to their M50 studs, so I'm guessing that's a good solution.

    I wonder if BMW's manufacturing tolerances for the drilling/tapping of the M50-based blocks are really that out of whack. Some people appear to have the problem, others work fine....

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    Could you measure all of your main holes and see if they are all the same depth? I wouldn't be too surprised to see they are slightly different, perhaps so much as to cause this discrepancy.

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    you know what i bet happened is that the arp's are supplied in an m50 length where the all the other e36's are 5mm longer. the m50 uses 75mm long bolts for the mains and the other e36 motors use an 80mm long bolt.
    do you even know what a plethora is?

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    Thats an interesting theory Drew


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    Quote Originally Posted by 5mall5nail5 View Post
    Thats an interesting theory Drew
    i am gonna go test it with the 2 blocks i have in the garage.
    do you even know what a plethora is?

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    Quote Originally Posted by ///M3 CRAZY View Post
    you know what i bet happened is that the arp's are supplied in an m50 length where the all the other e36's are 5mm longer. the m50 uses 75mm long bolts for the mains and the other e36 motors use an 80mm long bolt.

    It could also be that ARP know's that and just figured installers would back the studs out that last 5mm?

    I can't see what it would hurt..the actual torque on the fastener should be more accurate when the stud is suspended.

    I think the gent that posted his "link" in this thread actually talked to someone at ARP about this and they told him to not use the washer?? I would sooner back the stud out!!

    Don

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    ok so the theory WAS ok till i went outside. yes the m50 stud is definitely 5mm shorter. but the threaded block is the same depth. the 80mm s50 main bolt threads all the way in and can be torqued. so i am back to
    do you even know what a plethora is?

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    Quote Originally Posted by dcvee View Post
    It could also be that ARP know's that and just figured installers would back the studs out that last 5mm?

    I can't see what it would hurt..the actual torque on the fastener should be more accurate when the stud is suspended.

    I think the gent that posted his "link" in this thread actually talked to someone at ARP about this and they told him to not use the washer?? I would sooner back the stud out!!

    Don
    and we can agree that the stock bolt doesn't bottom out so why should the ARP's?
    do you even know what a plethora is?

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    Quote Originally Posted by ///M3 CRAZY View Post
    and we can agree that the stock bolt doesn't bottom out so why should the ARP's?
    If the ARP was a bolt we wouldn't have to worry about it. What happens to a stud that isn't bottomed out is pretty easy to picture. If its not bottomed, you torque the nut - there is friction on the nut. Once that friction is high enough (probably nearest the torque value), the whole assembly will want to compress and turn in the block. This will not torque the stud appropriately and will throw off your torque reading. If the stud is allowed to move down into the threaded hole, that means your reading will be off/wrong. Putting an insert in the hole, or bottoming out the studs, will be the only way of torquing the fastener properly.


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    you for sure don't want a bolt bottoming out.

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    Quote Originally Posted by 5mall5nail5 View Post
    If the ARP was a bolt we wouldn't have to worry about it. What happens to a stud that isn't bottomed out is pretty easy to picture. If its not bottomed, you torque the nut - there is friction on the nut. Once that friction is high enough (probably nearest the torque value), the whole assembly will want to compress and turn in the block. This will not torque the stud appropriately and will throw off your torque reading. If the stud is allowed to move down into the threaded hole, that means your reading will be off/wrong. Putting an insert in the hole, or bottoming out the studs, will be the only way of torquing the fastener properly.
    ok, so then since i have not dealt with this yet, is there anything in the top of the stud that will allow you to hold it in place? like on the top of a shock? if so then couldn't you hold the stud in place with that while applying the correct torque with a crows foot?
    do you even know what a plethora is?

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    Quote Originally Posted by 5mall5nail5 View Post
    If the ARP was a bolt we wouldn't have to worry about it. What happens to a stud that isn't bottomed out is pretty easy to picture. If its not bottomed, you torque the nut - there is friction on the nut. Once that friction is high enough (probably nearest the torque value), the whole assembly will want to compress and turn in the block. This will not torque the stud appropriately and will throw off your torque reading. If the stud is allowed to move down into the threaded hole, that means your reading will be off/wrong. Putting an insert in the hole, or bottoming out the studs, will be the only way of torquing the fastener properly.
    Agreed, and my machinist agrees too. We are going to try the S54 studs. They are 1/4" longer and, according to ARP, have the same thread diameter and pitch as the M50 stud. I think this is the answer.

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    Quote Originally Posted by ///M3 CRAZY View Post
    ok, so then since i have not dealt with this yet, is there anything in the top of the stud that will allow you to hold it in place? like on the top of a shock? if so then couldn't you hold the stud in place with that while applying the correct torque with a crows foot?
    There is an allen key hole, but its used to bottom the stud You can't fit a torque wrench over it (not a traditional torque wrench anyway). The real solution is not to hold the stud but to bottom it. Even if you loctite the stud in place I don't think I'd trust it. I mean you could mark the stud and the cap and see if it moves, but still... its designed to be bottomed.


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    Quote Originally Posted by S.Lang View Post
    Agreed, and my machinist agrees too. We are going to try the S54 studs. They are 1/4" longer and, according to ARP, have the same thread diameter and pitch as the M50 stud. I think this is the answer.
    There's only one thing to keep in mind - the threaded portion of the stud may not be longer. So if the thread portion is the same length or less and theres a shoulder at all on the stud it won't go all the way in either way. My machinist didn't use the washers and we bottomed the 201-5000 stud all the way in, fits perfect. He has done this before as long as the block/cap isn't aluminum.


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    Quote Originally Posted by ///M3 CRAZY View Post
    ok, so then since i have not dealt with this yet, is there anything in the top of the stud that will allow you to hold it in place? like on the top of a shock? if so then couldn't you hold the stud in place with that while applying the correct torque with a crows foot?
    Yes, there's a hex hole in the top of the stud that would allow you to insert an allen and hold it it place. But that's really there only for extraction purposes.

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    Quote Originally Posted by S.Lang View Post
    Agreed, and my machinist agrees too. We are going to try the S54 studs. They are 1/4" longer and, according to ARP, have the same thread diameter and pitch as the M50 stud. I think this is the answer.
    that is strange since the stockers are calling for the same 80mm length and use the same bolts as the s50 (same part number).
    do you even know what a plethora is?

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    Quote Originally Posted by 5mall5nail5 View Post
    There's only one thing to keep in mind - the threaded portion of the stud may not be longer. So if the thread portion is the same length or less and theres a shoulder at all on the stud it won't go all the way in either way. My machinist didn't use the washers and we bottomed the 201-5000 stud all the way in, fits perfect. He has done this before as long as the block/cap isn't aluminum.
    1. Do you feel that running the thread to the shoulder, whether bottoming or not, is not adequate? I mean, it is going to stop turning once it hits the shoulder, which really is the point in order to get an accurate torque reading, yes?

    2. Comparing the M50 ARP studs and S54 ARP studs, the threads that go into the block are about 3/16" longer, and the center unthreaded portion is about 1/8" longer, so it adds about 5/16" total length, which would appear to be perfect for my application.

    I really don't want to discard the washers, for two reasons - one, I think ARP, although someone there may say it's ok, includes them for a reason, and two, at the #3 and #5 main caps where the oil pump pipe brackets attach, you are still going to have the problem, as they are the same approximate thickness as the washers.

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    yes i did speak to arp direct. they gave me two options remove the washers or turn out the studs a bit..

    and as mentioned above i think turning out the studs is the best bet. since the stock bolts dont bottom out either.

    a few points IMO

    i dont see any benefit in bottoming out the stud the force of the TQ pulls away.

    also debris such as oil and other variables can make the holes seem shallow and forcing them to bottom out can cause fractures..

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    Quote Originally Posted by ///M3 CRAZY View Post
    that is strange since the stockers are calling for the same 80mm length and use the same bolts as the s50 (same part number).
    Intersting observation.

    Stock main cap bolts:

    M50 - M10 x 75 - p/n 11111735525

    M52 - M10 x 75 - p/n 11111735525

    S50 - M10 x 80 - p/n 11112244286

    S52 - M10 x 75 - p/n 11111735525

    S54 - M10 x 80 - p/n 11112244286

    It would appear that if your build starts life out as an S50 block (which mine did) you are going to have to go with the S54 ARP studs?
    Last edited by S.Lang; 02-26-2008 at 03:07 PM. Reason: found more info

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    Quote Originally Posted by s52e368 View Post
    yes i did speak to arp direct. they gave me two options remove the washers or turn out the studs a bit..

    and as mentioned above i think turning out the studs is the best bet. since the stock bolts dont bottom out either.

    a few points IMO

    i dont see any benefit in bottoming out the stud the force of the TQ pulls away.

    also debris such as oil and other variables can make the holes seem shallow and forcing them to bottom out can cause fractures..

    Carl the holes should be chased and cleaned thoroughly and bottoming the studs is what ensures proper torque specs. ARP/my machinist both say that running the washer is no big deal. The OEM bolts cannot be compared to the studs when talking about bottoming out. If you bottomed out a bolt you'd not be able to achieve the torque.


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    Quote Originally Posted by 5mall5nail5 View Post
    There's only one thing to keep in mind - the threaded portion of the stud may not be longer. So if the thread portion is the same length or less and theres a shoulder at all on the stud it won't go all the way in either way. My machinist didn't use the washers and we bottomed the 201-5000 stud all the way in, fits perfect. He has done this before as long as the block/cap isn't aluminum.
    Quote Originally Posted by s52e368 View Post
    yes i did speak to arp direct. they gave me two options remove the washers or turn out the studs a bit..

    and as mentioned above i think turning out the studs is the best bet. since the stock bolts dont bottom out either.

    a few points IMO

    i dont see any benefit in bottoming out the stud the force of the TQ pulls away.

    also debris such as oil and other variables can make the holes seem shallow and forcing them to bottom out can cause fractures..
    Both of you guys, very interested to know if the basis for your particular build was an S50 block!

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