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How to I.D. a 400 cid

Discussion in 'The Garage' started by Dafey, Apr 17, 2007.

  1. Dafey

    Dafey 1/2 ton status

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    I think I have a 400 according to the Vin :laugh: ,the 3rd letter is a R.How can I tell with out seeing behind the drivers side of the motor (I'm disabled ,its too hard for me to crawl up in there :laugh: )I haven't done a tune up yet,but it runs smooth it just has less power than Id expect from a 350 let alone a 400....Esp with headers and a 4barrel.My guess is the PO didn't re-gear it [which I haven't had time during the day to check either :rolleyes: ].If some one has a clear pic of a certain part of the motor for me to compare it too Id be very grateful :bow:
     
  2. goldwing2000

    goldwing2000 Guest

    Look for an externally balanced harmonic balancer, something like this:
    [​IMG]

    Also, some 400s have three core plugs (freeze plugs) on the sides of the block.
    Not all 400s have three but all that have three are 400s.

    That's about it, short of getting the casting number or yanking off one of the heads and looking for steam holes.
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    The balancer on a 400 is 8" diameter and so are many 350's. The way to tell is by either looking at the backside of the balancer for a piece that is cast irregular (external balance) or the flexplate will have a weight welded to the engine side of it (external balance).
     
  4. 54inches

    54inches 1/2 ton status

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    Well 400's only came in vehicles between 1970 to 1980.

    Casting #'s:

    330817......400...72-80...2
    3951509....400...70-71...4
    3951509....400...74-80...2
    3951511....400...70-73...4


    This is the best I can do for ya.
     
  5. Dafey

    Dafey 1/2 ton status

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    Sorry 54 , mines a 77,so it still could be...I hope so.
    And thanks guys !!
     
  6. Beast388

    Beast388 1/2 ton status

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    Probably the easiest way for the novice to determine if he has a 400 or not is to look at the harmonic dampner, which is what all of the crank pulleys bolt too.

    Since the 400 is externally balanced, the dampner will have some material removed around one side to act as part of the crankshaft counterweight.

    Here are a few pictures of harmonic dampners for externally balanced engines:

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    This is what a dampner looks like for an internally balanced engine:
    [​IMG]

    Hope that helps!:D






    Edit: Dang I'm slow.:doah: :haha:
     
  7. goldwing2000

    goldwing2000 Guest

    That's mine! :thumb:

    Out of a '72 Caprice. I still can't figure out why they put 4-bolt mains under a 2bbl carb, but I ain't complaining!
     
  8. Dafey

    Dafey 1/2 ton status

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    Thats perfect Goldwing & Beast.Thanks!!
    Shouldnt be hard to figure out. Getting under the front if I need to isnt hard.
     
  9. 54inches

    54inches 1/2 ton status

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    You are very welcome....compliments of moretec.com
     
  10. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Geeze, thanks. I gave you the most accurate info and i'm not even recognized. Guess i should have posted a pic to go along with what i said, goldwing2000 had to edit his post to make himself look good though since i posted in this thread. :rolleyes:
     
  11. goldwing2000

    goldwing2000 Guest

    Awww... poor widdle baby didn't get a pat on the back.

    Whatever.:rolleyes:

    And just fyi, smartass, I edited my post after I went to summitracing.com and started looking up dimensions on harmonic balancers so I could make sure I wasn't giving erroneous information.

    Yes, you should have posted a picture.
    And no, your information wasn't any more or less accurate than anybody else's.

    I don't know why you go around looking for shít to bitch about. Worse than a damn woman.
     
  12. Dafey

    Dafey 1/2 ton status

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    LOL sorry I was actually laying on the couch and dictated that to my wife to post,she told me two people posted pics and I told her to thank them...PLEASE forgive me :blush: :blush: :blush:

    These are the best pics I could get today,does it help?

    [​IMG]

    [​IMG]



    BTW does anyone know who this is,or I should say who made this trans?

    [​IMG]


    Im thinking the PO just put in a 350ci/th350 combo to replace the blown up pair that was in there.Beacuse the tag in the glove box says it had a 400ci and a M40 turbo hydramtic in it [ is that a th400?].

    And BTW again anyone know what a "UA1 4000 watt HD Delco F " is?

    {more questions to come tonight when I figure some stuff out :haha: }
     
  13. Dafey

    Dafey 1/2 ton status

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    LOL I think I need to make a "Questions/build" thread...:haha: :D What do ya think?
     
    Last edited: Apr 18, 2007
  14. 3 on the tree

    3 on the tree 1/2 ton status

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    I believe the 4000 watt Delco refers to the OE battery. For some odd reason, they used to rate them by watts.
     
  15. 54inches

    54inches 1/2 ton status

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    If you look at the harmonic balancer, you can see where it is reliefed on one side, so this makes this an exterally balanced engine.....400.....
     
  16. Dafey

    Dafey 1/2 ton status

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    Thanks 3 !

    So I really do have a 400? COOL!!!:bow: :D Thanks dude!!!

    Ok So what are these 3 other things guys? Besides the 4000 watt thing.
    EDIT:Is that the tires? Also whats the N41 Variable raito power?The steering?

    [​IMG]
     
  17. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    His picture does not show any relief on the balancer. He needs to rotate the engine 180* and snap another pic to confirm for sure.
     
  18. 54inches

    54inches 1/2 ton status

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    I can see two reliefs in both pics and none 180 degrees from those reliefs which would indicate balancing.
     
  19. Dafey

    Dafey 1/2 ton status

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    Ok I`ll do that tomorrow and feel behind it also for the relief.I couldnt feel any on the flywheel , but I wasnt that far under it either.
     
  20. 54inches

    54inches 1/2 ton status

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    Just as the 1st pic posted by beast 338 shows.

    Small drilled relief.

    Fairly clear to me, unless I am seeing something else.
     

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