Smog Pump Delete Plugs

Discussion in 'Small Block Tech' started by Double6skylark, Apr 19, 2018.

  1. Double6skylark

    Double6skylark Well-Known Member

    Anyone out there remove the smog pump system from their SBB? Looking to see what you used to plug the smog tube holes that connect to the head exhaust port. Thanks in advance for your help.
  2. 72gs4spd

    72gs4spd Well-Known Member

    Did that numerous times way back when. IIRC 3/8" pipe plugs were the ticket.
    Double6skylark likes this.
  3. Schurkey

    Schurkey Silver Level contributor

    I would expect that 3/8 NPT plugs can be forced into place, and easier if they're brass rather than steel.

    I bet what you actually need is INVERTED FLARE plugs.

    You'll know when you remove the AIR injection tubes from the exhaust. If the holes and tubes are set up as inverted flares...
  4. 36racin

    36racin Platinum Level Contributor

    Are you plugging the bottom side of the intake or the top where the air pump connects? I was just going to make a plate to go over the top of the air inlet
  5. Double6skylark

    Double6skylark Well-Known Member

    340 SBB.jpg
    I've tried 1/4 NPT pipe plugs which start to go in but stop a thread or two in. I also tried a 1/2-20 socket set screw which did the same...
    Is there something thats an iverted flare plug designed specifically for this?
  6. Double6skylark

    Double6skylark Well-Known Member

    The 1/4 pipe plug wouldn't fit so I'm assuming the 3/8 would be too big...not too familiar with pipe thread vs. imperial national coarse but I know they are completely different.
    Were these somthing you got from a hardware store?
  7. Double6skylark

    Double6skylark Well-Known Member

    I got the motor minus the smog equipment so I have nothing to check thread size on the male tube ends to.
  8. Schurkey

    Schurkey Silver Level contributor

    Shine a light into the AIR ports, see if there's an inverted flare seat machined into the iron.
    Any automotive parts store should have a rack or cabinet of brass fittings, although they're probably not going to have eight inverted-flare plugs. They might have two, and they'll be expensive.

    Or order them from Amazon. Pack of ten, $8.02. These are 1/4" (7/16-24 thread)

    Or 3/8 inverted flare pack of ten, $17.33 (5/8-18 thread)

    These are examples, you'll want to verify which size you need.
    Last edited: Apr 26, 2018
    Double6skylark likes this.
  9. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Just get a 1/4" pipe tap and make a 1/4" pipe plugs fit!

    You will be in control of how far it will go in by how far you thread the hole with the tap. Use grease on the tap to make the chips stick to the grease that is stuck on the tap for chip removal.

    Another option, rather than trying to find the "correct" threaded plugs. GL
    Double6skylark and Harlockssx like this.
  10. Double6skylark

    Double6skylark Well-Known Member

    Thanks @300sbb_overkill I've all efforts trying to find the right size plug....Going to pick up a 1/4 NPT tap and do as you suggested.
  11. SteeveeDee

    SteeveeDee Orange Acres

    If you look into the head and see a tapered seat that looks like a brake fitting, they will accept a 5/16" inverted flare plug, which are common as dirt at parts stores. The factory A.I.R. fittings were 5/16" inverted flare, for the tubing.
    MrSony likes this.
  12. Schurkey

    Schurkey Silver Level contributor

    Horse...water...won't drink...
  13. rhedelius

    rhedelius Well-Known Member

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  14. Brad W

    Brad W Miles from nowhere...

    It's odd that your valve covers only have 4 bolt holes and not six? I haven't seen that before and they have built in spark plug wire guides. Very cool!
    Double6skylark likes this.
  15. Double6skylark

    Double6skylark Well-Known Member

    I re-purposed the valve covers from the 300 I'm replacing.
  16. Double6skylark

    Double6skylark Well-Known Member

    I'm not sure on the removal of the smog pump as my 300 didn't come with one, but the 340 that I have has the smog pump ports in the heads tht I'm trying to plug.
  17. Double6skylark

    Double6skylark Well-Known Member

    Thank you, I realy appreciate any and all suggestions, tips, & recommendations. This is my first Buick and a first time for me to work on and restore a classic car so everything is new to me.
  18. Double6skylark

    Double6skylark Well-Known Member

    Unfortunately I don't have the smog pump sustem and tubes to compre the thread diameter & thread pitch.
  19. Schurkey

    Schurkey Silver Level contributor

    Do you have holes in your head?
  20. Double6skylark

    Double6skylark Well-Known Member

    Yes there are holes in the head just above the exhaust port. See picture earlier in this thread.

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