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Hot Rods C-357-B EDELBROCK triple deuce manifold question.

Discussion in 'The Hokey Ass Message Board' started by clem, Mar 7, 2024.

  1. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    Does anyone out there know what the thread / bolt size is for the threaded bosses on the above manifold which is a modern version that is still being sold new, - ( not one from the 1950’s )

    Particularly the right hand side ( rear ) boss that is under the vacuum can on the distributor.

    It appears that they are all tapped differently and I can’t find a bolt to suit.
    1/4 unf slides down inside and 5/16 unc won’t thread in as it seems too large.

    Metric bolts 8mm appears too large and 6mm too small.

    Is it possibly an oddball thread type, such as whitworth or something else ?

    any help would be appreciated, - thanks !
     
  2. bubba55
    Joined: Feb 27, 2011
    Posts: 521

    bubba55
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    Is it possible it’s pipe threads ? 1/4 npt
     
  3. onetrickpony
    Joined: Sep 21, 2010
    Posts: 863

    onetrickpony
    Member
    from Texas

    In guessing here, but maybe it is supposed to have a thread insert? Depending on what bolts on there, I would just run a 5/16 tap in it and call it good.
     
    Deuces and Tickety Boo like this.
  4. leadsled
    Joined: Apr 24, 2001
    Posts: 1,109

    leadsled
    Member

    I would think 1/4" NPT. I see you are from New Zealand, it's not identical but very similar to 1/4" BSP
     
  5. Oneball
    Joined: Jul 30, 2023
    Posts: 1,653

    Oneball
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    If it’s new I’d double check it’s not 5/16 UNC.
     
  6. Moriarity
    Joined: Apr 11, 2001
    Posts: 37,869

    Moriarity
    SUPER MODERATOR
    Staff Member

    Is this the manifold? is it the boss in the upper right on this picture? What is that boss even for? does the hole go through to the water p***age?
    c357.jpg
     
  7. Fordors
    Joined: Sep 22, 2016
    Posts: 6,548

    Fordors
    Member

    The NPT description means National Pipe Taper, 1/4”NPT is 1/4” ID pipe and the tapered thread, when measured at its midpoint will be approximately .530, so its not that.
    If you chamfered the hole a bit would the 5/16 bolt start in the thread?
     
    427 sleeper likes this.
  8. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 14,430

    Johnny Gee
    Member
    from Downey, Ca

    PDF install sheet makes no mention of it. Not what you like but is it for a temp sensor for engine management? If so, what thread do those sensors use?
     
  9. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 14,430

    Johnny Gee
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    from Downey, Ca

    ^^^^^ A little more poking around??? IMG_2535.jpeg IMG_2534.jpeg
     
  10. Moriarity
    Joined: Apr 11, 2001
    Posts: 37,869

    Moriarity
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  11. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 3,372

    427 sleeper
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    It's just a 5/16" threaded boss that doesn't go into water. Try running a tap in the hole to straighten out the boogered up thread's.
     
  12. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 14,430

    Johnny Gee
    Member
    from Downey, Ca

    ^^^^^ Then is it for ground wires?

    Not that I wanna know, because if I did I’d call Edelbrock myself.
     
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  13. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    yes, correct, that is the manifold, I downloaded a photo and then got distracted and forgot to post it.


    not open to any p***ages, just a boss and I wanted to put a clamp into it to hold a vacuum line.
    On the left hand side, the two bosses ( ***uming to hold throttle linkage) are both different sizes and the rear one appears to be the same as the one that I am questioning.

    sorry for the late responses, but we are on a bit of a time difference here.
    It was 11.00 pm here when I posted (and then I went to bed).
     
    Last edited: Mar 7, 2024
  14. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    Thanks, - we have NPT here, ( and not a tapered thread) and I didn’t try that, but I think that the thread is too co**** for npt.

    Can’t get a 5/16 UNC or UNF started.
     
    Last edited: Mar 7, 2024
  15. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
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    maybe, and that is what I thought it was, just measures smaller.
    At the moment the distributor is in the way, so that is the plan, to re tap a 5/16 thread
    if no one can convince me that it is something out of the norm, which of course is why I asked first.
     
    Last edited: Mar 7, 2024
    427 sleeper likes this.
  16. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    thanks,
    I did download the PDF sheet before I posted this thread, and like you, I couldn’t find any information about it.
     
  17. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    It is chamfered, and I still can’t start it.
    I will just re tap it.
     
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  18. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 14,430

    Johnny Gee
    Member
    from Downey, Ca

  19. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    Thank you gentlemen for all of your replies.

    as mentioned, I will probably just re tap, or if it is actually 5/16 UNC thread, just clean it up……..
     
  20. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    tried that also !
    ( I tried a lot before I asked here).
    It measured and looks like 7mm x 1.25, but I don’t think there is such a thing.
    I ***ume that they are made in America so will be standard imperial 5/16”.
    If made overseas it is more likely that someone could have inadvertently taped it with metric instead of imperial.
    Or -
    Maybe their tap is worn out, hence a smaller hole………..? :)
     
    Last edited: Mar 7, 2024
  21. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 14,430

    Johnny Gee
    Member
    from Downey, Ca

    None of it makes sense. Why is it there to begin with? And do we really want to know?
     
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  22. Just.dale
    Joined: Dec 4, 2018
    Posts: 410

    Just.dale
    Member

    Pretty sure this is the manifold I have sitting on a shelf, I’ll check when I get home after work.
     
  23. MCjim
    Joined: Jun 4, 2006
    Posts: 1,382

    MCjim
    Member
    from soCal

    There is an M 7.0 co**** thread
     
  24. Just.dale
    Joined: Dec 4, 2018
    Posts: 410

    Just.dale
    Member

    Mine seems to be the mirror image in the back of the one pictured above and the hole is not tapped. Is mine the older version??
     

    Attached Files:

    clem likes this.
  25. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 14,430

    Johnny Gee
    Member
    from Downey, Ca

    Yours makes sense when used on a 55 Chevy car. Trucks may have used that sensors position longer.

    Here’s both 2 and 4 barrel intake’s IMG_2536.jpeg IMG_2537.jpeg
     
    Last edited: Mar 7, 2024
  26. Just.dale
    Joined: Dec 4, 2018
    Posts: 410

    Just.dale
    Member

  27. leadsled
    Joined: Apr 24, 2001
    Posts: 1,109

    leadsled
    Member

    Can you get a thread pitch gauge in it?
     
  28. leadsled
    Joined: Apr 24, 2001
    Posts: 1,109

    leadsled
    Member

    1/8" npt is 27 threads per inch and female ID .380". It is often used for gauge line
     
  29. As has been said, it's a 5/16" course thread hole. As for your desire to use it to hold a vacuum line, that's how I used it as well. I made a small L-bracket out of stainless steel.

    20230120_134444.jpg
     
    Deuces, 427 sleeper and Fordors like this.
  30. clem
    Joined: Dec 20, 2006
    Posts: 4,705

    clem
    Member

    thanks for confirming this.
    At the moment I have run it around the other side and will just use a non traditional rubber clamp.
    I still don’t understand why on the other side the two holes are different ?
    Curious to know what yours are ?
    Although it is possible that they are both meant to be 5/16” co**** and the thread has been crossed and someone tapped it out to 3/8” co****.
     

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