2CV Bolt. What were they thinking?
  • Register
  • Help
Results 1 to 12 of 12
Like Tree3Likes
  • 1 Post By citroenthusiast
  • 1 Post By Ken H
  • 1 Post By jaahn

Thread: 2CV Bolt. What were they thinking?

  1. #1
    Fellow Frogger! pottsy's Avatar
    Join Date
    Sep 2002
    Location
    Melbourne, Northern Suburbs
    Posts
    901

    Default 2CV Bolt. What were they thinking?

    As we all know, Citroen are a lateral thinking bunch of Gauls, but lately I've been questioning their sanity somewhat.

    Firstly, I'm aware that there is an element of Citroeniste out there who view any minute variation from "Factory" as deviation of the worst sort and will perhaps react with a degree of pious fervour to my query, however, I've never subscribed to such illogical shenanigans so their protestations will be water off a Duck's back, so to speak.

    There are many areas of 2CV design which have my hand agitating my follicles, but the latest one seems to take the flat baked confection.

    The rocker shafts on the head are held at the top by the head bolts, but at the bottom by a Citroen Special Bolt with a head on it like a diseased pimple. Why is it so? I ask, summoning the Professor from my childhood.

    The head on this bolt is a rounded rectangle 6mm wide and 8mm long. Nominally it requires a special tool to remove and replace. In a pinch one can improvise with adjustable spanners or vice-grips, but we really shouldn't need to resort to these methods. I've had a go at milling out the end of a bolt to suit but unfortunately the ageing motor on the mill threw in the towel. A job for another day.

    The business end of the bolt is simply 35mm of high tensile M8 x 1.25 thread. Experiment and a bit of Internet searching shows me that a socket headed capscrew of the matching thread is a perfectly adequate subsitute.

    The head clears the rocker cover, the function is the same and as a bonus a standard tool will operate it.

    Advertisement


    Yet the usual suspects, sorry, suppliers, offer a special tool for this head as a matter of course so obviously people do remove and replace them.

    So can anyone shed some historical light on this conundrum? I doubt that Walter Becchia was such a devious designer that he did it out of spite. Surely there's a reason, but it's really not obvious to this retiree.

    Thoughts people?

    Cheers, Pottsy.
    Buvito Ergo Sum!

    The Fleet:

    2006 307 Auto 5 Door ("Spike" Mrs P's)
    1974 D Special Manual Sedan ("Moby Dick")
    2006 C5 HDI Wagon Auto ("Mephistopheles")
    1957 Slough 2CV ("Alphonse") Waiting in the wings
    1982 ex UK 2CV6 ("Gaston") On the road! (Woohoo!)
    Half of a 1984 2CV6Special ("The Alleged Vehicle")
    And for Fun, 1968 Mini Deluxe ("The R & D'luxe" 1078cc, Grin Factor 100!)

  2. #2
    Member
    Join Date
    Feb 2016
    Location
    North Yorkshire
    Posts
    50

    Default

    pottsy,
    you've hit the nail square on the head, since those peg bolts are a complete PITA.
    Replace with M8 cap head Allen screws, 35mm long, that's all...
    .
    ...except to say, avoid stainless screws.
    It took some time to extract a set of those from a pair of cylinder heads.


    Quote Originally Posted by pottsy View Post
    Thoughts, people?
    Cheers, Pottsy.

  3. #3
    Fellow Frogger! citroenthusiast's Avatar
    Join Date
    Apr 2014
    Location
    Phoenix, AZ
    Posts
    401

    Default

    Quote Originally Posted by Ken H View Post
    pottsy,
    ...except to say, avoid stainless screws.
    It took some time to extract a set of those from a pair of cylinder heads.
    Now I am curious. What happened with the stainless screws? I would think stainless steel, being relatively non reactive would be a reasonable choice.
    robmac likes this.
    Cheers,
    John T.

    61DS19 LHM BVH (son's); 67DS21 BVH; 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

  4. #4
    Fellow Frogger! Trading Estate's Avatar
    Join Date
    Oct 2010
    Location
    melbourne
    Posts
    482

    Default

    Seem to remember that two of the bell housing bolts on the traction are a similar dimension. David Gries had tool that fitted in a socket wrench. It looked like flattened 'cylinder'!
    '04 Megane
    Gone but not forgotten
    '71 16 TS, '72 16 TL, '74 15TS,'82 20TS Series 2, '85 25 GTX. '49 L15,

  5. #5
    Fellow Frogger! neural revolt's Avatar
    Join Date
    May 2005
    Location
    Frenchs Forest/Sydney/Australia
    Posts
    282

    Default

    Quote Originally Posted by citroenthusiast View Post
    Now I am curious. What happened with the stainless screws? I would think stainless steel, being relatively non reactive would be a reasonable choice.
    I think it could be a problem with galvanic action between aluminium and stainless steel. Could this be relevant to 2CV heads?
    I know we had this problem with radar antennas at Sydney airport; the s/s bolts became frozen into the aluminium antenna frames.
    Past Frogs:
    Alpine White 1967 R10 (round eye)
    Alpine White 1972 R16TS
    Blue 1978 Virage Wagon

  6. #6
    Member
    Join Date
    Feb 2016
    Location
    North Yorkshire
    Posts
    50

    Default

    My guess would be that lethal pairing which is far too common, 'brute force' plus 'ignorance'.
    Whenever I install Allen screws for this application, I use the same torque as specified for the cylinder head stud nuts; 2.5 kgf.m / 18 lb.ft., less an allowance for oiled threads.
    However, it would be very easy for someone who considers torque wrenches to be an irrelevance to apply something close to double that torque...



    Quote Originally Posted by citroenthusiast View Post
    Now I am curious. What happened with the stainless screws? I would think stainless steel, being relatively non reactive would be a reasonable choice.

  7. #7
    Fellow Frogger!
    Join Date
    Jan 2004
    Location
    Margate
    Posts
    346

    Default

    Quote Originally Posted by neural revolt View Post
    I think it could be a problem with galvanic action between aluminium and stainless steel. Could this be relevant to 2CV heads?
    I know we had this problem with radar antennas at Sydney airport; the s/s bolts became frozen into the aluminium antenna frames.
    That sounds about right to me. It's along time ago, but doing high voltage substation construction, you never had direct contact between stainless and aluminium due galvanic action. Galv to aluminum seemed to be ok through

    Driving - '90 XM, '85 CX IE Auto, 406 Coupe, 405 srdt wagon, '78 dyane, Resting (or Rusting): '71? Birotor '82 CX Presitige, '81 CX Break IE, GS X2, GS1015 Wagon, GS 1300 5sp Wagon, '76 GS 1220 Wagon, '75 GS Wagon, '58 2CV, '58 Vauxhall Velox

  8. #8
    Fellow Frogger!
    Join Date
    Apr 2016
    Location
    Bedford, UK
    Posts
    306

    Default

    Quote Originally Posted by pottsy View Post
    The rocker shafts on the head are held at the top by the head bolts, but at the bottom by a Citroen Special Bolt with a head on it like a diseased pimple. Why is it so? I ask, summoning the Professor from my childhood.

    The head on this bolt is a rounded rectangle 6mm wide and 8mm long. Nominally it requires a special tool to remove and replace.
    Are you any wiser on this Pottsy? On the DS, one (or two?) bolts holding the bell housing to the gear box (or the whole lot to the engine?) have 'special heads'. I'd assumed that these were meant to be 'tamper-proof' but why that would need to be case I can't imagine! I'd also be interested in the reason for your 'special' rocker bolt.

  9. #9
    Member
    Join Date
    Feb 2016
    Location
    North Yorkshire
    Posts
    50

    Default

    Err, for a galvanic cell to exist, don't the dissimilar metals need to be immersed in an electrolyte?
    If your engine oil is dosed with enough (saline?) water to render it conductive, you've got quite a problem...

    Quote Originally Posted by andrewj View Post
    That sounds about right to me. It's along time ago, but doing high voltage substation construction, you never had direct contact between stainless and aluminium due galvanic action. Galv to aluminum seemed to be ok through
    jaahn likes this.

  10. #10
    Member
    Join Date
    May 2014
    Location
    Sydney
    Posts
    90

    Default

    Pottsy

    The galvanic voltage difference between two dissimilar metals is given by a chart such as that given in this article: SSINA: Stainless Steel: Corrosion

    Between stainless and aluminium will oxidize (protecting the stainless even more) formed. An electrical path between the stainless and aluminiumneeds to exist and and access to oxygen. Process is accelerated in corrosive conditions.

    In non corrosive connditions it is fine with the galvanic potential barely above aluminium and brass which is pretty universal in engines.

    You might consider the strength difference between stainless bolts and non stainless. It is possible to get Allen headed bolts up to grade 12.9 in non stainless.
    - you will be lucky to get half that in stainless steel.

    I would assume the old citroen bolts to be around 8.8 grade.

    I have the same views on citroen querks - some are brilliant some are questionable - sometimes it takes some time to figure out the category.

    Alex
    Last edited by Arekisir; 15th October 2017 at 08:14 AM.

  11. #11
    Fellow Frogger! geodon's Avatar
    Join Date
    Jan 2013
    Location
    Geelong
    Posts
    344

    Default

    SS can be a double whammy.

    Apart from the galvanic reaction, has anyone tried to drill SS?

    I used SS rivnuts to attach the floor on an old land rover. Installing them with compressed air always puts a strain on the thread, and, sure enough, one stripped. No way I could drill it out! I had to put a bolt in.

    I shudder at the thought of a SS bolt snapped off in a cylinder head.
    "Pauses for audience applause......not a sausage!"....Bluebottle

    1949 Citroen Big 6
    1955 MGA1500
    1970 Peugeot 404 Utility (Resto project)
    1962 Renault Dauphine Gordini (Resto project)
    1950 Grey Fergie Tractor

  12. #12
    1000+ Posts
    Join Date
    Nov 2010
    Location
    Newcastle
    Posts
    1,891

    Default

    Quote Originally Posted by geodon View Post
    SS can be a double whammy.

    Apart from the galvanic reaction, has anyone tried to drill SS?

    I used SS rivnuts to attach the floor on an old land rover. Installing them with compressed air always puts a strain on the thread, and, sure enough, one stripped. No way I could drill it out! I had to put a bolt in.

    I shudder at the thought of a SS bolt snapped off in a cylinder head.
    Hi geodon
    There are several types of SS and they are not the same properties. I would have to brush up a bit to say more. but generally the corrosion resistant ones are a bit soft but some types are hardenable and can hold a sharp edge in a knife for instance.

    The softer type will "work harden" the surface very quickly if you attack it, with for example, a blunt drill and speed. The surface work hardenes as you go and the drill gets blunter and it all turns to sh*t rapidly as the drill turns blue as does the air The trick is to sharpen the drill first, and then using a slowish speed and pressure and lubricant, ensure it cuts in and does not rub and continues to cut till you are finished the hole. Easy peasy
    Jaahn
    cjl likes this.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •