Two Different Heads

Small Block Mopar Engine

  1. nodemon

    nodemon Well-Known Member

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    Just discovered my 318 2bbl has one 318 head and one 1967 273 head... I've owned it for for 7 months and am just now starting to work on it. Could there be and issue ..? Side note, I just bought a ld4b intake for it.
     
  2. JBurch

    JBurch FABO Gold Member FABO Gold Member

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    What year 318 are you dealing with? As a quick guess, not knowing year of your "Teener" I will hazard a guess that there are no worries to be had here, as in 1967 the 273/318 shared a common cylinder casting number 2658920.

    BTW what made you think there would be a problem?
     
  3. nodemon

    nodemon Well-Known Member

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    The block is a 73 warranty block..
    I had heard rocker arms / assembly might be different on the 273.. And just wondered about port size.. The heads I have, have two different casting numbers.. One is 68 -74 318.. Other is 67 273
     
  4. JBurch

    JBurch FABO Gold Member FABO Gold Member

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    Ports are the same size, types of rocker arms used have no influence on the heads themselves, regardless of style of rocker arm, they all bolt down the same. Based on my reference book "How to Hot Rod Small Block Mopars" I will say this: the 67 head is closed chamber, the other is open chamber. From 68 to 74 , they are all the same casting #: 2843675, with slight differences in finished chamber volume; which is larger than the 67 head. Look for another 67 head and you would be golden IF the difference bothers you. The 2 heads are for all intents and purposes, functional equivalents, if it were me I'd just bolt it together and not loose any sleep. You of course, can do what makes you feel good.
    Good luck.
     
  5. nodemon

    nodemon Well-Known Member

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    Really appreciate the feedback.. I'm not worried, at this point, about maximizing horsepower..just want it to run and not have issues.
    Again, appreciate the feedback..!
     
  6. 318willrun

    318willrun Utube channel 318willrun

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    one may have hardened seats for todays gas, and the other may not
     
  7. JBurch

    JBurch FABO Gold Member FABO Gold Member

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    What is the date cast of the other head? That casting number was used for 6 years.
     
  8. nodemon

    nodemon Well-Known Member

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    The 273 is a 1967 head
    The 318 is listed from 68 to 74
    Im not sure how to narrow it down...are there other numbers. ?
     
  9. cudamark

    cudamark FABO Gold Member FABO Gold Member

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    There are date codes cast into the head too. Starting sometime in '71, they started hardfacing the exhaust seats for unleaded fuel. I would match the heads to keep the combustion chamber sizes the same.
     
  10. 66fs

    66fs FABO Gold Member FABO Gold Member

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    You will have different compression ratios between the left and right bank of pistons. 675 casting has Open chambers (68 cc vs 920 casting has closed chambers (64 cc). I'd try to find another 273 head at best or another 318 head. Same port size, although the 273 head flows better as cast. Rockers will work the same, mechanical or hydraulic.
     
  11. toolmanmike

    toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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    I have 2 heads on my 273. Something happened in the life of that engine. I found one rod bearing stamped 71 also. You need to look at the casting numbers and look them up to see what they are. One is probably a #920.
     
  12. JBurch

    JBurch FABO Gold Member FABO Gold Member

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    Something just hit me........you know one head is a 67 273 head; how do you know? The other is 68 to 74 yet you do not know the date cast, how do you know it is a 68 to 74? I ask this because to know one head is a 67 273 head, you would need to know date cast and it follows that you say the other head is 68 to 74, you would also need to know date cast, yet you just stated you are not sure how to narrow it down.
    Something does not add up.
     
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    • nodemon

      nodemon Well-Known Member

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      Pulled up casting number page... The number on the 273 head is a one year only number.
       
    • nodemon

      nodemon Well-Known Member

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      Screenshot_20210715-135537.png
       
    • nodemon

      nodemon Well-Known Member

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    • JBurch

      JBurch FABO Gold Member FABO Gold Member

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      OK, for date cast, numbers will be present on one of the runners; top or bottom, I forget, it will be displayed month, day, year, the digits will be separated by dots
       
    • cudamark

      cudamark FABO Gold Member FABO Gold Member

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      If the casting number and in 920, it's one used in both '66 and '67.
       
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