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Technical Offenhauser Dual Port Carb, Gasket, this ain't right...

Discussion in 'Traditional Hot Rods' started by theloosecannon707, Sep 1, 2022.

  1. Hello Friends,

    Does the carburetor need to fit flush with a gasket and fit flush with the intake manifold around all these little crevasses? Because finding a gasket in this pattern aint happenin. I have tried to modify one but nothing is particularly close to this set up.

    How important is that the channels between those ports are sealed with a gasket? Is my carb smart enough to know the difference? Do I just need a gasket with the center line and leave the rest to fate?

    I don't know. Maybe you do.

    Also, just to address the incoming comments on "oh those are lame, gimmicky, they don't work, why don't you run something else, blah blah" Thats great, I'm with you... But that is not the questions. Let's just pretend that this is a question that should be answered for the universe, not the WHY am i using it, but the HOW can I use it.

    Peace, Love, and Earnest Tubb.

    upload_2022-9-1_16-24-17.jpeg
     
  2. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,722

    seb fontana
    Member
    from ct

    One flat gasket with 4 holes to match carb. Thats it.
     
  3. NoelC
    Joined: Mar 21, 2018
    Posts: 559

    NoelC
    Member

    It's called a base gasket. Not that expensive to buy. Or as a DIY you could as mentioned cut one out at home from gasket material with decent results. I'm sure there is some good science behind the cut outs but at the end of the day, it all goes in the same hole.
     

    Attached Files:

    Bob Lowry likes this.
  4. Almostdone
    Joined: Dec 19, 2019
    Posts: 788

    Almostdone
    ALLIANCE MEMBER

    The Engine Master’s series has an episode about carb spacers that seems appropriate here. They tested open and 4-hole spacers on single-plane and dual-plane manifolds. Check it out on You-Tube or Motortrend Channel on the TV.

    I won’t spoil the ending.

    John
     

  5. dan c
    Joined: Jan 30, 2012
    Posts: 2,414

    dan c
    ALLIANCE MEMBER

    go to the parts store, buy a sheet of gasket material and use a ballpeen hammer to make a gasket; i do it all the time!
     
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  6. NoelC
    Joined: Mar 21, 2018
    Posts: 559

    NoelC
    Member

    Go ahead John, spoil the ending for us. Those that don't want to know can look away or shield there eyes.
     
    Budget36 and '28phonebooth like this.
  7. carbking
    Joined: Dec 20, 2008
    Posts: 3,423

    carbking
    Member

    For WOT, it will not matter.

    For "little old lady driving" in the city, the gasket should match the intake. The intake was NOT designed and cast in this manner simply to make the intake more expensive!

    Jon
     
  8. NoelC
    Joined: Mar 21, 2018
    Posts: 559

    NoelC
    Member

    DO CARB SPACERS REALLY WORK? 4-HOLE VS OPEN (360 MAGNUM-HP & AF-FULL DYNO RESULTS) - YouTube

    Interesting enough (spoiler alert) guess they do, an they don't. But do they work isn't the way I'd phrase it.
    Because really, over all...if your not counting seconds, not worried about peaking out performance, torque and horse power, it's all going in the same hole. Like eating, it's all about how well you chew the food.

    I'm surprised no mention was made of the manifold? A polished up Offy 360, things a classic. Look at the new version below.

    [​IMG]

    I'm just saying...some of us don't need the edge a fraction of a second makes. But when I see the change in the cut out between the two, I have to ask myself, what does it matter and when don't it?

    [​IMG]

    That spoiler...an open plenum or a split plenum spacer gasket and buddies need for a gasket. If turbulence is given any thought, thickness of the gasket must be considered. As long as it seals between surfaces I don't it's going to matter much what he cuts for a hole.
     
  9. Thankseveryone, you all have been super duper helpful, and a real pleasure to get info from. Thank you.
     
    jimmy six and kadillackid like this.
  10. Almostdone
    Joined: Dec 19, 2019
    Posts: 788

    Almostdone
    ALLIANCE MEMBER

    Aw geez. Not doing our homework.

    The Engine Masters guys compared 1-inch open and 4-hole carb spacers with single plane and dual plane intakes on 383 Chevy.

    Ok, on a single plane intake a 4-hole spacer helped a bit more than an open spacer. On a dual-plane intake an open spacer helped quite a bit more than a 4-hole. Why? It came down to fuel distribution among the cylinders which was generally better out of the box with the single-plane than the dual plane. The open-plenum spacer aided mixing between the two engine banks with the dual-plane intake.

    So how does this apply to this thread you may ask? The question was “How important is that the channels between those ports are sealed with a gasket?”. I’d say it won’t matter, because the gasket is thin (no plenum volume change), and even if it did, more plenum volume on a dual-plane intake seems to be a good thing.

    It also seems to me that the notches between banks within primary and secondary sides should be open rather than covered up. Again, probably never know the difference.

    How’s that for over-thinking it?

    John
     
    Last edited: Sep 3, 2022
    NoelC likes this.

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