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using an early flathead manifold on a later block question

Discussion in 'The Hokey Ass Message Board' started by karfer67, Aug 20, 2009.

  1. karfer67
    Joined: Apr 5, 2008
    Posts: 119

    karfer67
    Member

    ok i searched and i could not find info on this. i just got a thickstun pm7 lowrise intake that is in sweet shape for free and a sharp 3 carb intake with 3 97's. i think i want to go with the 2 carb i hear they are easier to deal with on an otherwise stock motor which at first is what mine is. anyways i have a 50 shoebox and these are both early manifolds. i have heard that u can put an early manifold on the late block but what needs to be done if anything? thanks for the info ahead of time.
     
    Last edited: Aug 20, 2009
  2. carcrazyjohn
    Joined: Apr 16, 2008
    Posts: 4,843

    carcrazyjohn
    Member
    from trevose pa

    You have to redrill the intake manifold .The bolt angle on the heads are different.It's easy You will end up with an oblong hole.I made washers to hide this.
     
  3. karfer67
    Joined: Apr 5, 2008
    Posts: 119

    karfer67
    Member

    any more info on the mod? which way do i need to drill them and how much? thanks for the tip it is gonna take me awhile i still have to rebuild the carbs
     
  4. lakes modified
    Joined: Dec 2, 2001
    Posts: 1,283

    lakes modified
    Member Emeritus

    WTF: Just bolt it on. There is no change in the intake bolts.You need to determine the height of the fuel pump stand to see if it needs a shorter or longer pump rod.Have fun.
     

  5. 31ACoupe
    Joined: Nov 14, 2005
    Posts: 1,416

    31ACoupe
    Member

    I've never experienced having to modify anything, the ones I did just bolted on. There may be a few different bolt holes but it shouldn't matter. Also, I think the gaskets are a bit different but can't remember for sure.
     
  6. I believe carcrazyjohn is thinking SBC.
     
  7. 296 V8
    Joined: Sep 17, 2003
    Posts: 4,666

    296 V8
    BANNED
    from Nor~Cal

    Late blocks just have a few less bolt holes. I drilled the missing ones in my block but it's just a looks thing.
     
  8. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,681

    Bruce Lancaster
    Member Emeritus

    Also late blocks lack locating dowels, but usually manifold sits right vis a vis ports anyhow. Some early manifolds have same fuel pump stanf height as late, others are 1" lower. Can't remember which Thickstun is. You will also have to recreate a ventilation path for the engine, probably best done with early fuel pump stand for inlet and a hidden PCV as outlet.
     
  9. cuznbrucie
    Joined: May 1, 2005
    Posts: 2,567

    cuznbrucie
    Member

    You need to pull out the thin metal vent tube from the late model block towards the front of the galley....easy.....just use a pair of pliers.......otherwise the early manifold won't seat......that tube is up about an 1/8-3/16" above the intake deck.........use the early oil fill/breather tube.......

    I have the early style Thickstun PM-7 on a late block and it runs like a bear!

    CB
     
  10. doctorZ
    Joined: Apr 10, 2006
    Posts: 1,270

    doctorZ
    Member

    we just put a very early intake on a late model flattie here in the shop before bonneville, all we had to do was change the fuel pump push rod.
     
  11. karfer67
    Joined: Apr 5, 2008
    Posts: 119

    karfer67
    Member

    thanks for the info cant wait to toss this puppy on
     
  12. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    The only challenge is crankcase breathing. The early engines used a vent on the oil pan as an outlet and the oil filler at the fuel pump as the inlet. Later engines used the road draft tube as the outlet and the oil fill as the inlet.

    By putting an early intake on a late engine, you effectively have only one opening. So expect more blowby than normal as there's nowhere for the crankcase vapors to go but out the oil filler.

    It won't hurt anything, but depending on your engine, could be messy.

    The manifold will bolt on - be sure to check the fuel pump pushrod length as mentioned.
     
  13. karfer67
    Joined: Apr 5, 2008
    Posts: 119

    karfer67
    Member

    that is one of the issues i was thinking of. is there a way to add another breather?
     
  14. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    I've seen folks put a 90* breather on the pan...but as I said, it won't hurt anything, it could just be a little messy. It's done all the time.
     
  15. Toddjg
    Joined: Jun 9, 2008
    Posts: 202

    Toddjg
    Member
    from florida

    I have asked this same question before and got several answears from you can't do it to drilling holes in manifolds.
    The way I now understand this is to use old pump stand make sure push rod lenth is right. The early pumpstand breather will then act as a pcv/breather.

    Do I have it right?
     

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