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77 fresh air duct

Discussion in 'Tech Discussion' started by lcfman, Jan 2, 2019.

  1. lcfman

    lcfman Member

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    First Name:
    Geary
    Truck Year:
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    Truck Model:
    c20
    Engine Size:
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    I need a engine fresh air duct that run from the core support to the carb air cleaner (round to oval). The only part I could find is from LMC and it for later years '80's model but none for '77. The one LMC offers looks like it might work but I am not sure. Anyone know who sells one?
     
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  2. dvdswan

    dvdswan Full Access Member

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    I could be wrong, but I don't believe there was a duct on our year of vehicles. The original air cleaner neck was not designed for a duct to be attached.

    Now if you have a later year air cleaner installed then you would have to use those years.
     
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  3. lcfman

    lcfman Member

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    You could be correct I am not sure but my 77 C20 camper special has the radiator core support air duct connection and the air cleaner is oval and has ribs for air duct attachment. My old truck is pretty much a low mileage survivor with not much changed. It possible someone could have changed it but it doesn't look like it.
     
  4. Dougnsalem

    Dougnsalem Full Access Member

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    Man, I don't know. That sure seems like a lot of hassle and expense that may not be needed. My setup works great, and it was free!

    20190102_120129_Film2.jpg
     
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  5. Doc_Ellis

    Doc_Ellis Member

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    Truck Year:
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    I bought 2 ft of CAT 12 ducting from aircraft spruce https://m.aircraftspruce.com/catalog/appages/cat.php

    Both ends are round on my ‘76 250ci; not sure what you’d do about the round to oval thing. Maybe figure out a size you could squeeze down to work or they do sell flanges at aircraft spruce to go along with the ducts to maybe make an adapter?
    I think it’s pretty pointless to have on there in the grand scheme of things, and I’m hardly trying to build a show truck, but I do think it looks better with a duct than without; just for my own satisfaction.
    A351EA04-A7A3-4FC8-8007-9317624B68F2.jpeg
     
    Last edited: Jan 2, 2019
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  6. dvdswan

    dvdswan Full Access Member

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    Well if it is factory, you may have to scour junkyards to find one that works. It would be a lot cheaper anyway. I'm in the process of adding this, just need to pick up the ducting.

    LMC does show the ducting for 79-80 models. That may be what you need. I would look at the angle the neck comes from the air cleaner compared to the 81-86 model. The 81-86 is 3" longer. Part # 38-4358 and 38-4359.
     
  7. 75gmck25

    75gmck25 Full Access Member

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    My '77 K25 Camper Special has the oval air cleaner snout with ribs, and a round 4" plastic fitting on the passener side radiator support, but I've never found the right hose .

    I found one from a newer truck that was close, but the angles were molded in like it was designed to connect to the driver's side instead of passenger side.

    I also noticed that the radiator support has the same 4" punched out area on the driver's side, so the 6 cylinder picture that was posted now makes more sense.

    Bruce
     
  8. Craig 85

    Craig 85 Full Access Member

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    I got this one for my '79 from LMC. Fit perfect. I purchased a similar one for my K30. I didn't realize it was designed for a small block. I bought the silicone tube from Summit and adapted it to fit.

    '79 K15
    IMG_1096.JPG

    '85 K30
    IMG_1493.JPG
     
  9. Backfoot100

    Backfoot100 Full Access Member

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    I gotta tell you. I always thought that an aftermarket chrome plated open element air filter from K&N was about the perfect "topping on the cake" you could put on an engine. Functionally and aesthetically.

    Over the last couple of decades the cold air intakes have proven to be more functional performance wise than an open element filter sitting on top of the engine. Maybe not a huge amount more but keeping the engine heat out of the equation does make a difference.
    It amazes me that these trucks had the equivalent of a factory cold air intake that guys pay hundreds of dollars for now on the aftermarket.
    I think its pretty cool.

    I still think a well made open element filter is the bomb aesthetically but I must admit that I had to keep the factory setup for functionality.
     
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  10. Craig 85

    Craig 85 Full Access Member

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    @Backfoot100 I have to agree with you. The '79 I had actually ran better with the OEM set up than when I had an open element; especially in the summer. In addition to the cold air tube, I also added the taller OEM lid and filter for better flow.
     
  11. PrairieDrifter

    PrairieDrifter Full Access Member

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    Here is an 84 hose from lmc, it has a bend in it from the core support and shapes into an oval once it gets to the air cleaner.

    75285280-6763-43ED-BE97-540868929EE1.jpeg
     
  12. 78C10BigTen

    78C10BigTen Full Access Member

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    Sweet six ya got there! ;)
     
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  13. Doc_Ellis

    Doc_Ellis Member

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    Haha thanks! I love it, runs sweet and suits the truck perfectly
     
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  14. Backfoot100

    Backfoot100 Full Access Member

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    My Sub has the taller air filter cover already. When I replaced the air filter it was friggin' massive.
    After looking at it some more I may try and add a second air horn and hose to the air filter base out the drivers side to take advantage of the air duct built into that side of the radiator support. It would aesthetically be more symmetrical and relatively cheap to do. My thinking is that providing all the outside air flow possible in the Florida heat can only be a good thing.
    It would be the ultimate cold air intake and could look like a factory option if done right.
     
  15. Craig 85

    Craig 85 Full Access Member

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    Someone else on the forum did that same thing. IIRC they used the snorkels for an '87 and up. It was similar to this photo, but I think the driver side snorkel was flipped 180 degrees.

    2011-07-12_19-13-32_292.jpg
     
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