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Does it NEED to be there???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlazerWheels, Nov 29, 2003.

  1. BlazerWheels

    BlazerWheels 1/2 ton status

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    On my stock '85 Air cleaner housing, there is a built-in/hooked-on what looks to be like a thick screen filter /forums/images/graemlins/eek.gif. It sits inside of the filter. Does this NEED to be there? Can I remove it? It seems to me that it would slow/minimize the airflow...Any suggestions? /forums/images/graemlins/confused.gif
     
  2. Confedneck

    Confedneck 3/4 ton status

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    its probably there to prevent large debris from entering, i cant quite picture where it is you're talking about though..
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I'm pretty sure you're referring to the grey charcoal pre-filter. It's glued onto the bottom half of the stock air filter housing with some pretty heavy duty glue.

    The main reason it's there is to absorb extra fumes released into the air filter during cold start up. If the thermatic air cleaner is working properly, warm(and gas rich) exhaust is diverted into the aircleaner through the flexhose attached to the front of the passenger side exhaust manilfold. This helps the engine warm up faster.

    That said, rip the sucker out of there. The charcoal is probably deactivated by now anyways, and all the pre-filter does is restrict airflow. Less airflow = less performance. FWIW, I pulled mine off years ago.....
     
  4. Chevit

    Chevit 1/2 ton status

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    It is a spark arrestor in case you have a backfire up thru the carb. I took mine off a long time ago...
     
  5. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    The main reason it's there is to absorb extra fumes released into the air filter during cold start up. If the thermatic air cleaner is working properly, warm(and gas rich) exhaust is diverted into the aircleaner through the flexhose attached to the front of the passenger side exhaust manilfold. This helps the engine warm up faster.



    [/ QUOTE ]
    Look closer, Exhaust doesn't flow through that tube. Only hot air from the manifold is used that rises and opens that butterfly in the air cleaner tube. I am almost positive because there is no hole in my manifold, only sheet metal that wraps around to capture hot rising air.
     
  6. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Actually, you're wrong. Exhaust is indeed forced through the flexhose. During a cold start up, the EFE valve attached to the rear of the passenger-side manifold closes and the exhaust from the passenger-side manifold is redirected through the flexhose to the aircleaner to speed up warmup.

    When the temp sensor in the aircleaner reaches a set temp it sends vacuum to the diverter motor in the neck of the air cleaner and the valve opens to allow outside air in instead of exhaust.
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I was told that in addition to backfire control the charcoal in the pre-filter "trapped" rich exhaust gasses and let them out in a more controlled manner. /forums/images/graemlins/thinking.gif
     
  8. HarryH3

    HarryH3 1 ton status Author

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    [ QUOTE ]
    During a cold start up, the EFE valve attached to the rear of the passenger-side manifold closes and the exhaust from the passenger-side manifold is redirected through the flexhose to the aircleaner to speed up warmup.

    [/ QUOTE ]
    Sorry, but when that valve closes, it forces hot exhaust back through the exhaust crossover inside the intake manifold to help warm up the engine quicker. /forums/images/graemlins/eek.gif The flexhose indeed just draws air past the hot exhaust manifold and the heated air is used to prevent carb/throttle body icing. There's a thermostat in the air cleaner snorkel that determines when the heated air is required.

    The extra filter ring inside the housing is filled with activated charcoal and was part of the emissions system in some years. A spark arrestor would be used on the exhaust, not the intake. /forums/images/graemlins/cool.gif
     
  9. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Well if your exhaust manifold has a hole in it than there is something wrong. /forums/images/graemlins/frown.gif I have no hole in my manifold there only a sheetmetal device and the tube that wraps around the manifold to capture rising hot air.
     
  10. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Ok, but because the EFE valve causes backpressure from the passenger-side bank it stands to reason that the warmed exhaust gas will be forced through the flexhose and into the air cleaner, does it not?

    Fwiw, I knew about the crossover as well(ask me how I know), but I didn't think it was worth mentioning at this point.
     
  11. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Ahah, so that's where I'm going wrong on this. I've assumed all along that there WAS indeed a small hole in there somewhere........

    So can someone please explain to me how the warm air actually gets into the neck of the aircleaner? I mean, how much warmth actually reaches the carb if all it does is "waft" up into the flexhose?
     
  12. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    The preheater hose is required by the smog regulations out here because according to "experts" who have way more knowledge than me, when the door is closed, the warm air from the hose, which is attached to the exhaust manifold, goes into the TBI/Carb because the warmer air does something to the exhaust, which prevents a particular pollutant into the air.
     
  13. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    The reason the entire preheat system was introduced is because the faster the engine warms up, the sooner the choke fully disengages and the mixture leans out. That's why the Eco-Cops ensure that it's installed and operating properly.
     
  14. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    All I know is I hate the darn thing cause I run an open housing, and I have to install the stock housing when smog time rolls around.

    And to throw more tech out there, this system supposedly reduces the HC and CO emissions since it improves fuel vaporization.
     
  15. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]

    So can someone please explain to me how the warm air actually gets into the neck of the aircleaner? I mean, how much warmth actually reaches the carb if all it does is "waft" up into the flexhose?


    [/ QUOTE ] Have you ever put your hand over a candle or some sort of direct flame? Your hand gets hot very quickly.
    Same idea aplies, very hot air rises very fast.
     
  16. BlazerWheels

    BlazerWheels 1/2 ton status

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    OK, so before I go ripping off the charcoal filter, if it is gone will I not pass SMOG?? I have the heat sensor, and the butterfly and all of that(In process of fixing) but will it be okay to NOT have it?? IF so off it comes tomorrow... /forums/images/graemlins/confused.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/ears.gif
     
  17. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I took mine out a while back too and I have had it smogged since. I don't remember him looking inside the air cleaner. /forums/images/graemlins/thinking.gif
     
  18. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Yup, I understand the physics of heat. But since we're dealing with an engine that consumes gallons of air every minute I still can't see how much of a difference a little bit of heat(comparatively speaking) will make unless it was forced in.

    Secondly, with the thermo-valve shut, you have kind of a sealed system. The air comes from inside the housing on top of the manifold, through the flexhose and into the carb. SO how does the air get into the housing on the manifold? Is it hollow on one end?
     
  19. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Hold on, the heat that comes up through the tube isn't used to warm up the engine, all it is used for is to move that butterfly open and closed in the air cleaner tube.

    2nd Q,It is like a little box that wraps around the manifold with a round top that the flexihose sits on.
     
  20. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    [ QUOTE ]
    Yup, I understand the physics of heat. But since we're dealing with an engine that consumes gallons of air every minute I still can't see how much of a difference a little bit of heat(comparatively speaking) will make unless it was forced in.

    Secondly, with the thermo-valve shut, you have kind of a sealed system. The air comes from inside the housing on top of the manifold, through the flexhose and into the carb. SO how does the air get into the housing on the manifold? Is it hollow on one end?


    [/ QUOTE ]

    I swear, if I have to open up my book one more time for this tech stuff, I'm going on a pad spree in the Test Forum /forums/images/graemlins/rotfl.gif.

    The bi-metal (be cool if it was female /forums/images/graemlins/thumb.gif) door is set to operate at 50, 75, 90 or 120 degrees F. So with those numbers, it doesn't take long for the door to open back up, plus there's already a lot of air within that area that there should be no worries. /forums/images/graemlins/thumb.gif
     

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