warped carburetor base
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Thread: warped carburetor base

  1. #1
    Fellow Frogger! citroenthusiast's Avatar
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    Default warped carburetor base

    What are the accepted solutions for a warped carburetor base? I would prefer not to machine the carburetor since it will leave the base somewhat thin at the corners.

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    Cheers,
    John T.

    54 11BL; 61DS19 LHM (son's); 71DS21 BVH; 73SM 3.0; 73SM 2.7EFI; 73SM 3.0 (other son's); 74 Maserati Merak

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    Fellow Frogger! mberry's Avatar
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    You could go for the sandwich - 2 gaskets buttered with a mastic filling.
    Last edited by mberry; 22nd January 2017 at 07:26 PM.
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    the famous 18E pug206gti's Avatar
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    G'day,
    why did it warp ? Was the engine running a bit warm ?
    regards,
    Les W.


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    Yes, mastic sandwich.

    Roger

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    Mastic doesn't translate well to left-pondian. Would silicone RTV be the equivalent?
    Cheers,
    John T.

    54 11BL; 61DS19 LHM (son's); 71DS21 BVH; 73SM 3.0; 73SM 2.7EFI; 73SM 3.0 (other son's); 74 Maserati Merak

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    Quote Originally Posted by pug206gti View Post
    G'day,
    why did it warp ? Was the engine running a bit warm ?
    Hi Les
    The old carbies always warped. They were made of a poor quality diecasting alloy that was not nearly as good as later carbies. A usual problem in the good ol'days. Particularly when they sat on an insulating spacer which warped too under the pressure at the bolts.

    Use old fashioned gasket goo or similar. Silicon usually swells and causes problems in direct exposure to petrol like that application. Make an insulating spacer out of something solid like electrical base board and "fit it" to the curved base by filing and a thin gasket and Goo.
    Jaahn
    Last edited by jaahn; 22nd January 2017 at 07:06 PM.
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    Fellow Frogger! mberry's Avatar
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    Quote Originally Posted by citroenthusiast View Post
    Mastic doesn't translate well to left-pondian. Would silicone RTV be the equivalent?
    Yes, that should do it. Position sandwich before silicone has cured, then hand tighten, clean up any excess silicone (filling). Let silicone cure, then you should have a nicely shaped 'bespoke' gasket that you can then tighten firmly.

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    Quote Originally Posted by citroenthusiast View Post
    What are the accepted solutions for a warped carburetor base? I would prefer not to machine the carburetor since it will leave the base somewhat thin at the corners.
    While it's probably easier to flatten the carb base, to avoid the problem (and risk) you identify, what scope is there to shave the corners of the spacer to try to match the warped base? I'd rather cock-up and sacrifice a spacer than risk cracking a mounting point off my carb.
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  9. #9
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    Quote Originally Posted by jaahn View Post
    Hi Les

    Use old fashioned gasket goo or similar. Silicon usually swells and causes problems in direct exposure to petrol like that application. Make an insulating spacer out of something solid like electrical base board and "fit it" to the curved base by filing and a thin gasket and Goo.
    Jaahn
    Thanks for that, but I am having difficulty with language again..... In the states, "electrical base board" is a type of home heating appliance. The original spacers were, I believe, made of phenolic (Bakelite). Is that not a good choice?
    Cheers,
    John T.

    54 11BL; 61DS19 LHM (son's); 71DS21 BVH; 73SM 3.0; 73SM 2.7EFI; 73SM 3.0 (other son's); 74 Maserati Merak

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    Think I'd try grinding paste on a sheet of glass approach and look to get the base flat by hand.

    Cheers

    Marc
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    Cheers, Marc.

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    Quote Originally Posted by citroenthusiast View Post
    Thanks for that, but I am having difficulty with language again..... In the states, "electrical base board" is a type of home heating appliance. The original spacers were, I believe, made of phenolic (Bakelite). Is that not a good choice?
    Hi John
    Yea we speak 'strain over here !! Always hard to know what things are called somewhere else.

    As you said the spacers were made of something like phenolic but it seemed to be not as hard as today and yielded under the bolt pressure. What you need IMHO is a hard solid phenolic that will not give. Over here they make electrical meter boards and switch boards out of a very hard phenolic that I think would be good. That's what I had in mind.

    Do not use a soft gasket and spacer as it will just continue to warp the base more. A firm spacer shaped to the base and thin gaskets are best I think. Use an old fashioned type of sealant rather than silicon here because of the direct petrol exposure IMHO.

    I have tried to press the base of old carbies flat but the risk is high. That old metal is weak and can just give way suddenly. Even working on them can break the nozzles and lugs if you are not careful because they get weak. Treated carefully they can still work ok again.
    Good luck Jaahn
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    Machining a carburettor base?
    A bit of bush engineering (with a file) seems to work OK on A series carburettors with a warped mounting surface...



    Carburettor base after filing. by slcchassis, on Flickr
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    Quote Originally Posted by jaahn View Post
    Hi John
    Yea we speak 'strain over here !! Always hard to know what things are called somewhere else.

    As you said the spacers were made of something like phenolic but it seemed to be not as hard as today and yielded under the bolt pressure. What you need IMHO is a hard solid phenolic that will not give. Over here they make electrical meter boards and switch boards out of a very hard phenolic that I think would be good. That's what I had in mind.

    Do not use a soft gasket and spacer as it will just continue to warp the base more. A firm spacer shaped to the base and thin gaskets are best I think. Use an old fashioned type of sealant rather than silicon here because of the direct petrol exposure IMHO.

    I have tried to press the base of old carbies flat but the risk is high. That old metal is weak and can just give way suddenly. Even working on them can break the nozzles and lugs if you are not careful because they get weak. Treated carefully they can still work ok again.
    Good luck Jaahn
    You can buy the suitable carb base with gaskets. . .
    Insulating spacer for under carburettor
    Fibre spacer block with gaskets for under Weber and Solex double choke carburettors fitted to 1985cc, 2175cc and 2347cc engines.

    This block can get warped along with the base flange of the carburettor and allow air to get sucked in which upsets the running of the car.
    Cheers
    Chris
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    Quote Originally Posted by mberry View Post
    Yes, that should do it. Position sandwich before silicone has cured, then hand tighten, clean up any excess silicone (filling). Let silicone cure, then you should have a nicely shaped 'bespoke' gasket that you can then tighten firmly.
    Silicone RTV is not recommended for any Engine gaskets

    https://www.permatex.com/products/ad...esive-sealant/
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  15. #15
    Real cars have hydraulics DoubleChevron's Avatar
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    Quote Originally Posted by Ken H View Post
    Machining a carburettor base?
    A bit of bush engineering (with a file) seems to work OK on A series carburettors with a warped mounting surface...



    Carburettor base after filing. by slcchassis, on Flickr
    the trouble with filing them flat .... Is it is then much thinner and much weaker so will rapidly bend again However now it's flat, how about a much stronger new custom made insulator for beneath the carby so it will not be able to bend under the bolt pressure .... That should work well

    seeya
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    Hi Chris. I forgot to mention that this is a 24/32 DDC from a DS-19, so the late model spacer won't fit. It has almost a full millimeter of warp, so if I want it flat, I will fly cut it. I just hate to remove metal, because you can't put it back.

    I like the gasket sandwich + permatex (hard curing gasket compound) idea and I can get electrical grade Garolite sheets (fiberglass reinforced phenolic) from McMaster to make the spacer.

    Thanks everyone.
    mberry and jaahn like this.
    Cheers,
    John T.

    54 11BL; 61DS19 LHM (son's); 71DS21 BVH; 73SM 3.0; 73SM 2.7EFI; 73SM 3.0 (other son's); 74 Maserati Merak

  17. #17
    Real cars have hydraulics DoubleChevron's Avatar
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    I just remembered why you shouldn't file/sand/mess with the carby base. Buttercup Bob found years ago if you did this, when you bolted the carby back on, the body would slightly bend again causing the throttle butterflies to stick

    seeya,
    Shane L.
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    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


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  18. #18
    Fellow Frogger! citroenthusiast's Avatar
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    Shane,

    Thanks for that confirmation. I am having Dave Burnham ream and bush the primary throttle shaft - it is pretty bad... (see photo). The last thing I want is for the shaft to bind later on.

    warped carburetor base-throttle-shaft-gap.jpg
    Cheers,
    John T.

    54 11BL; 61DS19 LHM (son's); 71DS21 BVH; 73SM 3.0; 73SM 2.7EFI; 73SM 3.0 (other son's); 74 Maserati Merak

  19. #19
    Real cars have hydraulics DoubleChevron's Avatar
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    Quote Originally Posted by citroenthusiast View Post
    Shane,

    Thanks for that confirmation. I am having Dave Burnham ream and bush the primary throttle shaft - it is pretty bad... (see photo). The last thing I want is for the shaft to bind later on.

    Click image for larger version. 

Name:	throttle shaft gap.jpg 
Views:	195 
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ID:	93208
    Wow, I can even see the base is curved there too ! That is one well worn carby
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    '63 ID19 http://www.aussiefrogs.com/forum/showthread.php?t=90325
    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


    Modern Junk:
    '07 Poogoe 407 HDi 6spd manual

  20. #20
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    Quote Originally Posted by Ken H View Post
    Machining a carburettor base?
    A bit of bush engineering (with a file) seems to work OK on A series carburettors with a warped mounting surface...



    Carburettor base after filing. by slcchassis, on Flickr
    I have done the same for my CX with a Weber 34DMTR and also my Tractions with Solex 32PBIC. The problem of distortion is exacerbated by ham fisted over tightening onto the Phenolic insulator base. Only very thin gaskets should be used between the insulator and carb and between the insulator and induction manifold.
    Cheers Gerry

  21. #21
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    I would say the cardy is on its last legs!!!!

    Old Holden trick, (less complicated carb base pattern)...

    Get a suitable peice of thick cow hide and cut out pattern. Now boil...yes boil.... in a hard grease, (like machinegun pack and store grease, (i used to have a box of blocks a few years back)). While still hot and slightly liquid assemble parts and just tighten down a bit...let cool and re-tention.

    Not run engine up to full temp and recheck tention. The leather wll harden up with exposure to fuel over time.

    Note...a smear of copper cote on the alloy surfaces will allow the gasket to come off in the future. However in this case the next time you dissasemble it you will be tossing it away!

    If there is the chance of sucking in the gasket soak the dry hide gasket in locktite or superglue and assemble. The superglue will be absorbed by the leather and eventually set solid.

    Future removal of the carby will be done by the next owner of the car!!!
    /// 1986 SII 505 GTI
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