Exhaust Stud Tightness Question?

Discussion in 'Engine, Fuel and Exhaust' started by Hoople, Jul 17, 2011.

  1. Hoople

    Hoople Account Removed

    7,198
    0
    34
    None of this makes any sense to me. Two weeks ago I installed a set of SE slip-on's. In addition to just installing them, I wanted to remove the header pipes and install new HD header gaskets in order to make sure I would have no leaks once the install was finished. Pulled everything apart, cleaned and inspected all fittings. Installed new wire mesh gaskets in each cylinder head. Installed the new HD header pipe SS wire mesh gaskets along with grade 8 header studs. Torqued the stud nuts to 120 in/lbs. Installed the slip-ons. Road the bike & all seemed perfect.

    The next morning after the bike cools off, I once again torque the header studs to 120 in/lbs. I expected they would settle in. Rode the bike, let it cool and once again the torque wrench would not "click off" until they were tighten a little more. The following day, once again the same thing. And again and again and again....
    This has been going on every day for 10 days. The exhaust flanges are just about flush with the head (I think one actually is).

    I don't get it. Will these exhaust nuts ever terminate to a tightness of 120 in/lbs and stay there.
    I know the nuts are not actually loosening. They are going deeper and deeper, that much I know. It seems if I had tighten them just once and stopped there, in a short time the pipes would have a leak.
    It is like the heat is actually crushing the rounded fitting on the end of the header pipe each time the engine expands. I really don't have a clue and I don't want to take it all apart to see...

    Is there a problem or is it normal? Should the flanges be flush with the head?
    The book called for 120 in/lbs.
     
  2. Jack Klarich

    Jack Klarich Expert Member

    18,544
    153
    399
    Hoop, I have gone over the torque on my exhaust nuts I don't know how many times. I got so sick of it I chucked the H D nuts in favor of lock washers and new grade 8 nuts. Have you bottomed out the new studs in the heads? To me the flange should not be bending like that, tho I have seen alot of Dynas loosen up the exhaust nuts just because, I think it is the way the exhaust is mounted to move with the engine pulses, I could be wrong Jmo, let me know what you find and I know you will
     
  3. ballpeen

    ballpeen Active Member

    172
    18
    1
    I found the same thing, my resolve was after the third time was to just leave them alone, they have not leaked in over two years now. I'll be waiting to see what some of the guys say on this one.. Take Care
     
  4. sharpscuba

    sharpscuba Banned

    945
    0
    1
    Hoop I had the same problem on my 07 Electra glide. I ended up just changing the nuts just like Jack did.
     
  5. Hoople

    Hoople Account Removed

    7,198
    0
    34
    From what I can tell the flange is not bending at all. It is just pressing squarely toward the cylinder head, evenly on both sides. As best as I can tell (without taking it apart) it just seems like the folded over "flare end" of the header pipe is just forming or shaping to the contour of the receiving shape of the head and SS mesh gasket.

    As you know the head studs are made up of two different thread pitches (24 & 18 per inch). I do have the 18 (course head thread) bottomed in the head.

    At this point there is not much I can do except leave them alone because the flange is almost flush and square against the head. I will just double nut it and leave it alone for now.

    Thanks for the replies. It really helps because I thought I was seeing things or going crazy!.
     
  6. Iceman24

    Iceman24 Well-Known Member

    3,224
    48
    13
    Hoop; similar deal w/my TD's, but only rear cyl. Front torqued to spec & dead-on every time I check & rear cyl keeps wanting more...?? Ended up "double-nutting" stud & left alone for now. Thinking about taking a look this winter to ensure I didn't over-crush the rear gasket.
     
  7. gator508

    gator508 Senior Member

    2,314
    68
    81
    Hoople,

    I have done the same thing over and over, installed lock washers and grade 8 nuts as Jack suggested, I still have to check the torque from time to time, it seems only the rear cylinder exhaust needs it, front remanis tight. I assume this is just part of routine maintenance.
     
  8. Hoople

    Hoople Account Removed

    7,198
    0
    34
    It can't be looked at as routine because in my case it gets loose again with just 1 heat cycle. There has to be something strange going on for this to happen.

    I am thinking the grade 8 studs I installed have a smaller coefficient of expansion than the pipe and flange, thereby resulting in a crushing effect of the tailpipe. I just don't know.
     
  9. gator508

    gator508 Senior Member

    2,314
    68
    81
    You may have a valid point there, it will give us all something to ponder, I would like to know the outcome of this, maybe check with the experts from the HD shop.
     
  10. dangerdan

    dangerdan Junior Member

    922
    26
    0
    Not sure if this applies.
    The book says to torque one stud to 8 in/lbs.
    Torque the other one to 120 in/lbs.
    Torque the first stud upto 120 in/lbs.

    Repeat the process for the other cylinder.