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Thread: Replacing OEM head bolts with ARP Studs

  1. #1
    Join Date
    Jan 2014
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    1995 BMW M3 Turbo

    Replacing OEM head bolts with ARP Studs

    Hey,

    I have 9.0:1 pistons with stock head bolts, running 12 psi without problems. I want to increase boost to about 16-18. So I got me some ARP studs and now am stuck on what the best way to install them is. I don't want to replace the head gasket, and I will be attempting this without removing cams. What I gathered from some reading is that the two main ways of doing this is

    a) undo all OEM bolts at once, then install ARP studs, or
    b) undo OEM bolt, install ARP stud and torque to OEM spec, one at a time. Afterwards go through and retorque all per ARP spec.

    If I do option a, will the head gasket still be ok? If I go with option b, is it possible that OEM spec has higher torque than the ARP?
    Which route should I take?

    Will appreciate any insight.

    Thanks.
    Last edited by BensM3; 09-02-2014 at 07:49 PM.

  2. #2
    Join Date
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    96 332IS 6466 turbo
    Arp spec is 85 ft lbs. Some go higher.
    1996 332IS
    Built 3.2
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  3. #3
    Join Date
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    89 635csi 384/493 @18psi
    Quote Originally Posted by BensM3 View Post
    Hey,

    I have 9.0:1 pistons with stock head bolts, running 12 psi without problems. I want to increase boost to about 16-18. So I got me some ARP studs and now am stuck on what the best way to install them is. I don't want to replace the head gasket, and I will be attempting this without removing cams. What I gathered from some reading is that the two main ways of doing this is

    a) undo all OEM bolts at once, then install ARP studs, or
    b) undo OEM bolt, install ARP stud and torque to OEM spec, one at a time. Afterwards go through and retorque all per ARP spec.

    If I do option a, will the head gasket still be ok? If I go with option b, is it possible that OEM spec has higher torque than the ARP?
    Which route should I take?

    Will appreciate any insight.

    Thanks.
    Arp torque will be higher than oem. If it were me I would not take them all out first. My car has 12mm arp, recommended tq was 90 I think I did 95. You will definitely need to torque again after running up to temp or after a few days.

  4. #4
    Join Date
    Oct 2007
    Location
    Montreal, Quebec, Canada
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    45
    My Cars
    1999 BMW M3 COUPE
    Did mine at the beginning of the summer. I removed one bolt at a time in the order given on the spec sheet provided in the arp's box. I did 85 ft.lb right away and after the 14 were done, I checked them again with 87. I just put 2 more pounds to make sure I had the 85 spec because torque wrenches may not be as accurate as we think. Who knows?

    Even tho I did not used the car much, it is still holding :P .

    By doing it one at a time would lead me to think that the gasket should not move.

    The only challenge is to align the nut on the stud! Take a magnet and a flat screwdriver!

  5. #5
    Join Date
    Jul 2011
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    Bay Area, California
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    M3 w/Gt35r
    It's essential that you torque them down and then let them settle for a good amount of time. Maybe not as much because you're not removing the head and you're not compressing a thick MLS gasket, but definitely something that shouldn't be overlooked. IIRC when I removed all the stock head bolts to remove the head, coolant began to leak out near the back of the engine. Personally, I would do it one at a time.
    My torque sequence consisted of 35ft lbs.- 65ft lbs.- 85ft lbs.

  6. #6
    Join Date
    Jun 2005
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    virginia beach
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    Turbo S52 E39 M5
    Definitely one at a time, and install in torque sequence

  7. #7
    Join Date
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    Pittston, Me
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    92 535i, 93 325is 01 X5
    +1

  8. #8
    Join Date
    Jan 2014
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    Mill Creek, WA
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    1995 BMW M3 Turbo
    Exactly what I was looking for. Will do one at a time then. Thank you much.

  9. #9
    Join Date
    Apr 2012
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    Tampa, FL
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    E36,E38, and E46
    its probably common knowledge but you still want to iron the head out. start in the center and work you way out.

    xx0xx
    xx0xx

    x0xxx
    xxx0x

    xxx0x
    x0xxx

    0xxxx
    xxxx0

    will keep you from developing a "bubble" between the block and head.

  10. #10
    Join Date
    Dec 2011
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    Holland, bish!
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    Euro e36 M3 3.2 cabrio
    Not saying you shouldnt do it but here is some technical background info that can help you decide on how you want to tackle this job;

    Installing studs and then using higher clamping loads without honing the bores at this clamping load with a torque plate will distort your bores roundness which can result in leaking piston rings, or at least 4 shiny spots that don't retain oil in the bores after some use. How many miles other people have successfully done with their similar setup gives no guarantees for your engine.
    It is amazing how flexible and soft such a rigid piece of steel actually is by the way!
    Also; undoing the bolts one by one is possible but you do risk warping the head; you create a very large local amount of difference in stresses in the aluminium as you are not untightening the entire head in sequence. Besides overheating it is the number one reason for warped heads. Number 2 is undoing heads whilst they are still too hot.

    Good luck

  11. #11
    Join Date
    Jul 2004
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    Sid Knee
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    325is, 96 M3 Euro
    some of the older engines had issues with faulty headbolts and the BMW fix was a different bolt replaced one at a time in a specified sequence... i would worry about the extra warping the extra boost will compensate. address that if you tear it down
    Last edited by digger; 09-06-2014 at 02:16 AM.

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