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Intake gasket restrictor plates- need some info....

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by FWP, Nov 24, 2001.

  1. FWP

    FWP CRS

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    I'm putting together a 350 SBC, and need some info. The exhaust crossover on the intake gaskets have a bunch of different options for adding the restrictor plates to the gaskets- ie. left, right , both or none.......What's the deal? I'm not sure of the block year (77?) or does it make a difference? I guess it's for heating the fuel mixture(what I was told), but I don't quite get the whole picture[​IMG]. Why restrict one side and not the other, or both, or none? Help me understand, so I can put this motor together the right way[​IMG].... Thanks guys.

    <a target="_blank" href=http://coloradok5.com/gallery/75K5>http://coloradok5.com/gallery/75K5</a>
     
  2. Twiz

    Twiz 1/2 ton status

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    Don't know about restricting one side or the other, I would think it's all or nothing.
    The intake has a passage that runs from one head, under the intake and carb pad to the other side. It serves three prurposes.
    1- Heat the intake charge. Heated intakes will vaporize the fuel, vaporized fuel will burn cleaner and therefore, lower H/C emmissions . (a single partical of fuel, with 14 particals of air srounding it = "perfect" combustion) A heated intake will also help re-intriduce fuel that may have dropped out of the air stream.
    2- EGR port, this passage under the intake also feeds the EGR valve exhaust gasses used to reintriduse into the intake charge. The exhaust gass in the intake charge reduse combustion temps, and lower combustion temps lower NOX emmisions.
    3- Help with cold starts and cold weather drivability. Gets the engine up to temp quicker.

    Not the best set-up from a performance stand point, but it works. Unless steps are taken to help with cold-starts and cold-drivability, the passage shoud be left open. If the intake manifiold has the correct passage built into it, most dual plane intakes have this passage.

    <font color=blue>Twiz
     
  3. DesertDueler

    DesertDueler 1/2 ton status

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    What do you mean steps to help cold weather, my Firebird has no choke, no bypass and has no problems with cold starts other than it stumbles before it goes until the motor gets up to 160 degrees:) Just have to get use to it I guess.

    86Jimmy 4"&35"MTRs,87 burb 4"&35"MT,69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>
     
  4. Twiz

    Twiz 1/2 ton status

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    It all relitive. You don't drive your 'bird in the snow, right? I would expect, a truck would be more commonly used in the harsh enviroments.

    Everything is a comprimize, loose some drivability to get some performance. And vice-versa.

    <font color=blue>Twiz
     
  5. azblazor

    azblazor 1/2 ton status Premium Member

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    We just went through this last summer. It was real hard to find info. Let me go did in my reference stuff and I'll post back.

    <font color=blue>azblazor</font color=blue>
    <font color=orange> 79 K5 454-FI / 4L80E, NP205, D60, FF14, 4" lift, 9K Warn </font color=orange>
     
  6. azblazor

    azblazor 1/2 ton status Premium Member

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    Here is some info I have on the intake gasket restrictor:
    <a target="_blank" href=http://community.webshots.com/scripts/editPhotos.fcgi?action=showMyPhoto&amp;albumID=18931435&amp;photoID=25923030&amp;security=cbdUbByTJb>http://community.webshots.com/scripts/editPhotos.fcgi?action=showMyPhoto&amp;albumID=18931435&amp;photoID=25923030&amp;security=cbdUbByTJb</a>
    here is the text if you can't read it:
    1955-72: All cars and trucks take the open port heat-riser gasket. That's the
    top one of this photo.
    19731 All 302-350-400 cars and tight trucks take restricted left side (viewed
    from driver's seat) and open on right. 350 heavy duty, that's 3/4 ton capa-
    city and up, take open left and right.
    1974: 350-400 car and truck applications with two-barrel carburetor use
    restricted left, open right, 350-400 car and truck applications with four-
    barrel carburetor use restricted both sides, but heavy-duty 350 with four-
    barre! carburetor uses open both sides.
    1975: All 262-350-400 light truck and cars use restricted gasket on left,
    open on right. 350 heavy-duty applications with two-barrel carburetor use
    open both sides. 350-400 heavy duty with four-barrel carburetor use re-
    stricted both sides.
    1976: All 262-350-400 four-barrel carburetor applications use open gaskets
    both sides. 305-350 with two-barre! carburetor and 350-400 with four-
    barrel carburetor to California emission standards and 350 trucks with
    four-barrel carburetor use restricted left, open right. 350 heavy-duty with
    two-barrel carburetor uses open both sides. 350-400 heavy-duty with four-
    barrel carburetor use restricted both sides.
    1977: Alt cars and light trucks use restricted gasket on left side. 350 heavy-
    duty trucks with two-barrel carburetor use open gaskets both sides. 305-350-
    400 heavy-duty trucks with four-barrel carburetor use restricted both sides.

    Hope this helps

    <font color=blue>azblazor</font color=blue>
    <font color=orange> 79 K5 454-FI / 4L80E, NP205, D60, FF14, 4" lift, 9K Warn </font color=orange>
     
  7. DesertDueler

    DesertDueler 1/2 ton status

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    You kidding me drive it in the snow. I only drive it in the rain if I am already out and it rains, it has no windshield wipers. Anyways it doesnt snow here in Phoenix so we dont really need the bypass. Now AZblazor if you head up north alot then I would say to use it but if not dont worry about it a block of both sides for a litle more power.

    86Jimmy 4"&35"MTRs,87 burb 4"&35"MT,69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>
     
  8. FWP

    FWP CRS

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    Thanks guys for all the help[​IMG]. I get it now. I'm going to restrict both sides (not completely cut off), and use the hot air intake (thermac) for cold weather startups.

    <a target="_blank" href=http://coloradok5.com/gallery/75K5>http://coloradok5.com/gallery/75K5</a>
     

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