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Bypassing all Emissions and Smog devices

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Ditchdigger, Mar 11, 2001.

  1. Ditchdigger

    Ditchdigger Registered Member

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    My 84 K-5 is stock with a 305 Q-jet(hope to be 350 down the road). but, my question is: can you bypass the Vapor Canister and PCV systems including the AIR pump and pipes going into Exhaust Manifolds?
    Basically, have a bone stock V8 with a breather in place of PCV and whatever plugged vacuum ports on carb that were for emissions and still run good, If I did have to make carb adjustments all I'd hopefully need to do would be Air/fuel mixture screws Right!

    One more thing! when the engine is cold it accelerates fairly good but, as soon as she warms up it dogs out when I accelerate unless I push the pedal slowly also seems like she's strugglin at highway speeds and I only have 31x10.5s R15s with a 700R4 which leads me to believe its carburetion and the timing has been checked but not the vacuum advance!

    If it ain't intimidating / It ain't a Chevy!
     
  2. Triaged

    Triaged 1/2 ton status

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    I would say to run the emissions stuff. It really doesn’t take up that much horsepower. However since you probably won't listen to me anyway...For a daily driver don't get rid of the PCV valve. It helps remove all the blow-by gases from the engine and doesn’t rob any HP at all.

    '71 Blazer CST with alot of rust
     
  3. ragtop

    ragtop Registered Member

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    I removed the AIR pump on mine when I installed the hedders but, the previous owner had already removed the cat conv. I'm not sure what, if any, effect it would have on the cat, if still there, to remove the air pump. Mine's computerized so it adjusted but, when I did similar to my 81 camaro I had to change metering rods in the Q-Jet to richen it back up to normal. I agree with Triaged that you should definately keep the PVC as it provides negative crankcase pressure to remove blow-by. If your gearing is high (i.e. 2.73s) with a 700R4 in OD and you went to 31s, your engine is running way too slow at highway speeds to have any power. I changed to 3.42s when I went to 31s to compensate for the larger tire diameter and speed the engine back up to where it was with stock tires.

    '88K5 - 350TBI, 700R4, 208, 3.42 10 bolts w/Auburns & 31s
    Ragtop - [​IMG]
     
  4. wayne

    wayne 3/4 ton status

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    This is what a friend of mine and I did to his 83 Z28 and it made one hell of a difference. Not sure if you have a computer to deal with but we did and we wanted to eliminate it in the process.

    1. Put a pipe in place of the cat. converter.
    2. Put in a very mild cam. Don't remember the specs but it was not much bigger then stock. The factory cam went out and that is what started the whole thing.
    3. Put a non computer controlled carb and HEI distributer on it.
    4. Put an electric fan and costom built 3 core radiator in.
    5. Pulled off all emission crap and plugged any holes that we needed to.
    6. Put a PCV valve in one side and a good breather on the other side.

    After we did all of that we had no problem cutting high 13s on the 1/4 and would keep up with a Corvette on the top end. That car pulled harder then most 350s I road in.

    <A target="_blank" HREF=http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html>http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html</A>
    <font color=blue>Happy Trails[​IMG]</font color=blue>
    <font color=blue>Wayne</font color=blue>
     
  5. Ditchdigger

    Ditchdigger Registered Member

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    Thanks for the info guys,
    I'm gonna get rid of the AIR and Canister
    but, I agree on the PCV so I think I'll keep it
    not much life in the motor left anyways
    so it can't hurt anyways!

    If it ain't intimidating / It ain't a Chevy!
     
  6. DMK

    DMK 1/2 ton status

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    The canister vents your gas tank by using engine vaccum.It basically recycles gas fumes from tank instead of venting into the air. It uses no horsepower. If you remove it make sure you buy a vented gas cap, if you can find one that will fit. I would leave it on.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah, and don't forget that cannister has a tube running up to the engine compartment that will need to be plugged as well. Else you will have the possibility of gas entering the engine compartment...reminds me, I need to do something to mine...probably put the cannister back but hook nothing else up to it, and hook it up to the unused EGR (timed) vacuum port on the carb.



    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  8. Ditchdigger

    Ditchdigger Registered Member

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    In my reasoning its another headache to contend with
    there have been so many times in the shop where I've had to reconnect lines to there right places and finding god knows how many cracked lines and then disrupts the whole thing!
    Hey, dyeager535 what you mean after (Probably) in your message!

    If it ain't intimidating / It ain't a Chevy!
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah sorry..I mean that there is an open to atmosphere fuel tank vent in the engine bay when you pull the cannister....didn't think I was going to have to deal with the EVAP (cannister) but turns out that the hose was on the frame, and the sending unit is specific for evap. Have to pull the tank or just re-route the damn hose into the carb so that it burns the vapor off instead of putting it into the atmosphere...although maybe I'll just plug it and get an older vented gas cap instead.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  10. olbluebeast

    olbluebeast Registered Member

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    would you have a schematic of where all those damn lines go? PLEASE HELP........CHRISH9252@YAHOO.COM
     
  11. olbluebeast

    olbluebeast Registered Member

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    WHAT EXACTLY DOES THE CANNISTER DO? WHERE DO ALL THE LINES GO THAT I PULLED OFF WHEN I SWAPPED THE ENGINE OUT. I COULD NOT REMEMBER WHERE THEY ALL WENT AND MANY WERE DAMAGED. I CAN'T SEEM TO FIND A DRAWING THAT SHOWS WHERE ALL OF THEM GOES . BUT I KNOW THE VACCUM IS NOT RIGHT BECAUSE THE CRUISE CONTROL NO LONGER WORKS.. HELP ME WITH A SCHEMATIC IF YOU HAVE ONE E-MAIL ME AT chrish9252@yahoo.com. it is for a 83k5 fwd with a 350, it has a new smog pump, but i thing i need the cannister, o2 sensor replaced. just what is an egr valve, is that another name for something i call doomaflachie? thanks in advance for any help fellow shade tree mechanics and pros.
     
  12. Ditchdigger

    Ditchdigger Registered Member

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    the charcoal cannister stores fuel vapors from gas tank and carburetor for use at a later time primarily at higher RPMs
    the cannister has valves on the top that open at higher throttle and suck the vapors to be burned putting it basically,

    the vacuum lines are hard to put into words where they go because I would end up with a novel explaining it, just get yourself a good mechanics book like Chiltons available at any NAPA or Checkers and it has schematics on the lines for many setups. I have had to mess with Vacuum lines all the time and basically know by heart where they go and even not knowing why it goes there I just know it from fixing hoses all the time and rerouting them because someone else didn't do it right!
    I doubt your cannister needs to be replaced maybe your valves do on top but sometimes the whole shebang is pretty cheap not sure if your engine is stock though because alot of aftermarket carbs don't have the necessary ports, The EGR stands for (Exhaust Gas Recycle)It controls when exhaust gases get back-routed to the Intake where it can be burned again therefore, lowering Emissions and this usually all happens at higher RPMs! hard to say about your Cruise control these years were always a bit finicky you should have no trouble with cruise just find a main vaccum source and plug into control box and then to the throttle diaphragm, but if you have all the lines disconnected and every vaccum source plugged and can't believe it would be running correctly! I have thought about getting rid of everything except the PCV system on my blazer but not sure of the outcome on how it would be running
    How is yours running with everything disconnected except the Dist. advance and vacuums plugged and do you have a stock setup and why are you hooking it all up!
    glad to help!

    If it ain't Intimidating / It ain't a Chevy!
     

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