Torquing N* head
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Northstar Engines and System Technical Discussion Discussion, Torquing N* head in Cadillac Engine Technical Discussion; Well I have a Northstar down to the heads...that was not fun...but anyhoo .... Side note...this is a 97 service ...
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    Tailfin's Avatar
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    N* Headgasket torquing procedure

    Well I have a Northstar down to the heads...that was not fun...but anyhoo ....

    Side note...this is a 97 service manual and I'm doing it on a 96...but I trust that doesn't matter--same engine.

    I'm a little confused about the torquing procedure given in the service manual. I have scanned the page in question here...
    headgasket3.jpg

    The highlited spots are the one I'm confused about. The first one just sais feet...not foot-pounds. I thought maybe they meant that anyway, but then the put "pound feet" by the other bolts, plus the conversions between the N-m and the feet/feet-pounds/whatever are different. Could someone clarify this bit for me?

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    98eldo32v's Avatar
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    Re: N* Headgasket torquing procedure

    The 3 M6 bolts are the ones near the timing chain. The others are the head bolts themselves

    ----------

    Which repair method did you chose?

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    Re: N* Headgasket torquing procedure

    DO NOT torque - or attempt to torque - those 3 bolts to 106 lb/ft. !!!!!!!

    Use an online conversion engine to get lb/ft for Nm. Google "foot pound to newton meters"

    The head bolt (10) sequence and degrees is correct. The initial torque establishes base bolt tension, the additional rotations set the bolt stretch. I hope you used either BigSerts or NS300L inserts.

    USE NEW BOLTS !

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    Re: N* Headgasket torquing procedure

    I did the conversion and the first number seems to be correct... 30 N-m is 22.12... foot pounds...just seems like they messed up printing this. As long as it's the right number, I have no issue with it...but that's the sorta thing to make one nervous . Seems kind of light actually, considering it's only getting another 120 degrees, but I'll follow. I just noticed taking some of the old ones out...they were really in there.

    Yeah no worries. I have new bolts and I'm using the NS300L inserts.

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    Re: N* Headgasket torquing procedure

    I am sure they simply (mistakenly) omitted "lb" in the first number. It should have read "lb/ft".

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    Re: N* Headgasket torquing procedure

    Quote Originally Posted by Ranger View Post
    I am sure they simply (mistakenly) omitted "lb" in the first number. It should have read"lb-ft".
    Fixed

    Fun fact - torque is equivalent to the force (lb) multiplied by the length of the moment arm (ft). There is no division. Interesting the the 'ft/lb' error is somewhat common, yet we never see the same mistake applied to the metric unit, shown as 'n/m'.

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    Torquing N* head

    I've just put the heads back on my N*. I'm using the NS300L inserts...and I'm just a bit nervous on the experience. With the inserts, I carefully followed the instructions to the letter. The thread locker says to let dry 3 hours before putting in the head bolts...To remove doubt, I watied 2 days. I was also careful to use brake cleaner and compressed air to make sure the holes did not have oil residue.

    What I don't like is while doing the second "60 degree" turns (as per the manual) in some of the bolts, I felt the wrench kind of "give" for just a moment, and had this unpleasant image of the inserts breaking loose inside the block. Now I don't understand why that would happen...because they claim that bolts have broken before these things give...and plus, I'm going clockwise...and I don't see why the inserts would want to go that way, since it would be pulling them further into the block...but I don't like that it acted that way, just the same. It's my first headgasket. Anyone had any similar experience?

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    Re: Torquing N* head

    I know exactly what you mean by "give" when fastening the bolts back.

    I understand that you have taken the utmost of care in the preparation of the block for the inserts, but again ANYTHING can happen sometimes.

    You are now screwing a bolt into an insert. Rotating clockwise probably the same way the insert was installed.

    I'm not saying those inserts don't work, they must have worked for a few people with great success but, that "give" feeling I've felt too often dealing with soft metals such as aluminum.

    That is part of the reason I'll never use inserts, for me it's studs or nothing.

    I don't know if you've ever had one of those studs in you hand, but once that is installed correctly it's not going anywhere. Again, anything can happen but the northstar is too much of a beast to work on to second guess.

    I always say, fix it and forget it.

    I truly hope you don't have a problem later...........

    Good luck.

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    Re: Torquing N* head

    I actually e-mailed Norm (the guy who sells these inserts). He said it was not uncommon for this to happen, because the bolts are long and the bolt itself can twist a little, and then the threads catch up. I'm inclined to believe this because it does make sense to me, and it happened on severaly bolts.

    I will post back if I do have a problem...if I haven't commited suicide lol

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    Re: Torquing N* head

    He stated this was common?

    WOW!!!

    I think that would be a little unnerving when you go this deep into the motor KNOWING these things have head gasket retention issue, especially in the aluminum block area.

    I pray you have no problem, my friend.

    Studs....... to the end.
    CadillacLuke24 likes this.

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    Re: Torquing N* head

    Well, it's not unnerving if the give is simply the flex in the bolt. If that is the cause, then it would still happen even if the block were steel. All the same, I too hope I have no problems :-P.

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    Re: N* Headgasket torquing procedure

    Ok lordy... I have a follow-up on this issue...these service manuals are making me as nervous as the engines themselves. I've just put the heads back on and followed the above procedure for torquing....that is, first pass 22 ft-lbs, then 2nd and 3rd pass, 60 degrees. I was reading through an old sticky thread on these head gaskets, and I found a post by AJ (the fellow who did a whole write-up on this subject) as follows:

    Quote Originally Posted by AJxtcman View Post
    Torque Specifications:

    1993-1999 Head Bolt Torque
    • First Pass ----- 30 lb ft
    • Second Pass -- +70°
    • Third Pass ---- +60°
    • Fourth Pass -- +60° (190 Degrees total)



    2000-2003 Head Bolt Torque:
    • First Pass ------ 30 lb ft
    • Second Pass -- +70°
    • Third Pass ---- +60°
    • Fourth Pass -- +45° (175 Degrees total)



    2004-2008 Head Bolt Torque:
    • First Pass ------ 22 lb ft
    • Second Pass -- +60°
    • Third Pass ---- +60°
    • Final Pass ---- +60° (180 degrees Total)
    Here is a link to the actual thread:

    http://www.cadillacforums.com/forums...ure-fix-4.html

    I'm finding this very disturbing... ALL of them have a 4th pass, and my manual page as I scanned up there, doesn't. Also, I have a 96 (97 manual), and the figures he posted don't even start with the same torque as my manual says. Can anyone help me clarify what's correct here? This is not a job I need to do twice :-P.

    ----------

    Sorry edit post is messing up for some reason...I realize maybe he meant 30 N-m and put lb ft....but the last pass...that's really bugging me out...

    ----------

    G'ah! I've just checked ALLDATA, which I have...and I found an "update" for this procedure....and the update has just what AJ put in his post...so it seems like GM screwed up printing, without exception, the most important torque specs in the manual...GRR. Next question...will it cause any problems for me to loosen the bolts and do it properly from there?

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    Re: N* Headgasket torquing procedure

    Northstar head bolts are torque to yield. Once used - even if improperly - you must use a new set.

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    Re: N* Headgasket torquing procedure

    Now you see why per se' WHY I won't use inserts.

    You're making three more passes torqueing the head in place, into an insert that may possibly move a bit?!


    It's hard to say whether or not to redo them.

    As you torque the head, you crush the gasket.

    If you've only done 3 passes and there is a 4th, I'd say you'll be ok.

    Yet, this is an area of repair that you don't what to have a shadow of a doubt about what is going on.

    You may want to get new head gaskets and start all over for peace of mind.

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    Re: N* Headgasket torquing procedure

    Ugh... Yeah I see the issues at hand. Part of me likes the idea of just doing a 4th pass...but the updated service bulletin STARTS at a different torque...not much, but still. Plus, even the bolt order is different. I think if I were to loosen them, then that first torque setting would not be correct if the bolts are deformed. What a mess... This isn't a problem with the inserts... I don't mind the process of new bolts or even gaskets... I do mind the prospect of being out another $120 just because the GM manual people were morons...

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