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Technical 239 flathead aluminum heads question

Discussion in 'The Hokey Ass Message Board' started by chop cut drive, Sep 3, 2015.

  1. chop cut drive
    Joined: May 18, 2010
    Posts: 41

    chop cut drive
    Member
    from central pa

    does any one know what size bolts i need to use on these aluminum heads factory ones not long enough. i dont want to use studs. I know studs are 3'' an 3.25" long but not sure if thats to long of a bolt. Please help Thanks
     
  2. flathead4d
    Joined: Oct 24, 2005
    Posts: 876

    flathead4d
    Member

    What kind of heads and what engine block do you have? 49 to 53 8-BA or 48 and back.
     
  3. RichFox
    Joined: Dec 3, 2006
    Posts: 9,760

    RichFox
    ALLIANCE MEMBER

    Well, you know how thick your heads are. And you can easily determine the depth of threads in your block, or how far do the stock bolts thread in with the stock heads. Common rule is 1 and 1/2 times the diameter of the bolt for threads. Or maybe a little more for good luck. So you put those numbers together and round off to some normal size and you should be good to go. By using common sense.
     
    J. A. Miller likes this.
  4. 29AVEE8
    Joined: Jun 28, 2008
    Posts: 1,384

    29AVEE8
    Member

    Flathed Fords have a specific "class of fit". You can't just put any bolt in there and not have them leak. Who made the head? They should know the length required. Then go to Mac VanPelt, Joblot, ARP etc for the specific part. Oh and don't use a tap to clean the threads in the block, they will leak for sure.
     
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  5. chop cut drive
    Joined: May 18, 2010
    Posts: 41

    chop cut drive
    Member
    from central pa

    They are offenhauser heads an I called the place where I got them with no help. Richfox I was going to do that but just wanted some other opinions, good minds think alike thanks
     
  6. chop cut drive
    Joined: May 18, 2010
    Posts: 41

    chop cut drive
    Member
    from central pa

    Oh its a 239 51 block v8 8ba
     
  7. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don
    Member

    There are a few places on that block where just a bit to long will bottom out and not hold the head down.
     
  8. I don't know why you wouldn't want to use studs, far superior clamping force on a bi metal engine setup that will have the head walking around as it settles. They're also easier on the block threads which are easy to pull right out of the casting with bolts.
     
    rmcroadster likes this.
  9. Be prepared to torque & retorque & retorque your heads over initial couple hundred miles.......as mentioned, these will walk around on you and need to take a good set........pay attention to correct sequence & settings for torquing .......
     

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