View Poll Results: Which is better?

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  • Center Mount

    4 100.00%
  • Front

    0 0%
  • Rear

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Thread: Center/Front/Rear Mount Adapter

  1. #1
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    Center/Front/Rear Mount Adapter

    Pulled my motor last weekend and started looking at the TBI to square bore adapter I ordered from trans-dapt and what less than impressed. Would require removing material from the intake for a smooth transition and I am not keen on doing that to a brand new intake, especially if down the road I decide to change it out and sell it.

    So, given my career in rapid prototyping and CNC milling capabilities at my job, I started to design my own with smooth transitions to the width of the square bore intake.

    In my design I got to thinking what is the benefit of TBI positioning on the intake. I don't want to starve any cylinders relative to one another so I would assume that center plates or slightly forward mount would be best for that? Currently I am setup in a forward mount spot even with the front of the intake port. I've seen other people design these on here and wanted to see if anything stands out as being better.

    This is what I've got so far.
    Attached Images Attached Images

  2. #2
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    If I can remember to snap some pictures I have a square bore to 2" bore Marine TBI adapter off a 405 HP Mercruiser 502. It is approximately 2" tall, and has a tapper all the way from the top of the 2" bore to the spread bore oval flanges.

  3. #3
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    Quote Originally Posted by Fast355 View Post
    If I can remember to snap some pictures I have a square bore to 2" bore Marine TBI adapter off a 405 HP Mercruiser 502. It is approximately 2" tall, and has a tapper all the way from the top of the 2" bore to the spread bore oval flanges.
    Fast I assume this is a center mount setup?

    My spacer is designed to be .75" minimize the height of the breather when it's all together. Don't think I will run into hood clearance issues with a full size truck, but don't want to make it gargantuan either.

  4. #4
    Super Moderator dave w's Avatar
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    Pics are "D Shaped / Port Volume Matched" square bore TBI adapter plate. Send me a PM for the STEP file. Original file is .pkg format.

    TBI_Adapter_SquareBore_Port_Matched_01.jpg

    TBI_Adapter_SquareBore_Port_Matched_02.jpg



    dave w

  5. #5
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    Cut this out, based off of dave w. design last night. 6061 Aluminum.

    Fits my performer RPM nicely. I didn't bother to do clearance work from the bottom side, so it isn't truly "port matched" in my case, but I think will work nicely for me. Still need to polish the tooling marks out of the bore taper, just didn't have time last night. IMG_1664.jpgIMG_1669.jpgIMG_1666.jpg

  6. #6
    Super Moderator dave w's Avatar
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    dave w

  7. #7
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    Honestly I would not polish it and leave it slightly rough. I might even go so far as to take a small cuttoff wheel and a dremel and purposely carve ridges in it. The reason behind that is so it will help atomize any raw fuel droplets that might try to collect and run down the bore of the spacer. I often add the same grooves on the intake manifold ports for the last 2 inches of each. Liquid fuel does not burn, vapor burns.
    Last edited by Fast355; 08-04-2018 at 07:31 PM.

  8. #8
    Fuel Injected! geewhiz's Avatar
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    PM sent

    I'm putting a '87 7.4L TBI with the factory adapter on an amc 360, with Edelbrock Performer carb manifold.

    Thanks
    John

  9. #9
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    Quote Originally Posted by geewhiz View Post
    PM sent

    I'm putting a '87 7.4L TBI with the factory adapter on an amc 360, with Edelbrock Performer carb manifold.

    Thanks
    As the design belongs to Dave I am not at liberty to produce these. I will say I have had it on the engine now for 2 years or so without any issues and seems to work fine. I would recommend Dave get them produced and market the design but in truth the amount of machining required may make it not feasible in terms of price to demand. When you consider cost to produce would likely be around $300-400 per part youre halfway to buying a holley sniper at that point.

  10. #10
    Super Moderator dave w's Avatar
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    Quote Originally Posted by bgott View Post
    As the design belongs to Dave I am not at liberty to produce these. I will say I have had it on the engine now for 2 years or so without any issues and seems to work fine. I would recommend Dave get them produced and market the design but in truth the amount of machining required may make it not feasible in terms of price to demand. When you consider cost to produce would likely be around $300-400 per part youre halfway to buying a holley sniper at that point.
    The adapter could be affordably manufactured Off-Shore (at or about the Trans-Dapt prices . . . https://www.hedman.com/carb-to-efi-adapters), minimum production run of 1000 units. My pocket$ are not that deep. Trans Dapt isn't buying my idea either

    dave w

  11. #11
    Fuel Injected! geewhiz's Avatar
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    That's all right, I thought someone offered the step file above. I can make the measurements and make my own.
    John

  12. #12
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    Quote Originally Posted by dave w View Post
    The adapter could be affordably manufactured Off-Shore (at or about the Trans-Dapt prices . . . https://www.hedman.com/carb-to-efi-adapters), minimum production run of 1000 units. My pocket$ are not that deep. Trans Dapt isn't buying my idea either

    dave w
    Mine Either! Something tells me it would be hard to sell 1000 of them too, unfortunately.

  13. #13
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    Quote Originally Posted by geewhiz View Post
    That's all right, I thought someone offered the step file above. I can make the measurements and make my own.
    Dave's design is very nice and although a simpler adapter could be machined very simply, his requires 3D surfacing toolpaths to produce but the benefit is that the cross section of the hole is constant (at least that's how I understood it) and allows the wider throttle body holes to comfortably transition into a square bore intake. That was my impetus for making it when I did.

  14. #14
    Super Moderator dave w's Avatar
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    Holly has drawings available for the TBI.

    https://documents.holley.com/gm_2-bbl__3_bolt_.pdf

    Holley has drawings available for the 4150 / 4160 squarebore.

    https://documents.holley.com/square_..._4150-4160.pdf

    Holley has drawings available for the Spreadbore

    https://documents.holley.com/spreadbore.pdf

    dave w
    Last edited by dave w; 06-25-2021 at 11:18 PM.

  15. #15
    Fuel Injected! geewhiz's Avatar
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    THANKS DAVE!!!! Those will come in very handy as I try to make an adapter. I think that is the route I'm going, I'll make an adapter, and not use the "water doughnut", I think that's what I've heard it called, the stock 7.4L adapter.
    John

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