Author Topic: Air tube check valve replacement  (Read 302 times)

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Offline snowfighter10

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Air tube check valve replacement
« on: October 11, 2020, 01:35:54 am »
The air injection tube that attaches to the rear of the exhaust manifolds on my engine has a blown check valve. As some of you know a bad check valve will allow exhaust gasses to travel back to the smog pump causing it to seize. The T shaped tube and check valve assembly is no longer available for purchase new.
1988 W100 SWB, 5.2 TBI, NP435 4-speed.

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    Offline snowfighter10

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    Re: Air tube check valve replacement
    « Reply #1 on: October 11, 2020, 01:39:16 am »
    After I removed the tube from the motor I cut the bad check valve off with a tube cutter. Then I threaded the end of the tube with a 3/8 NPT die.
    1988 W100 SWB, 5.2 TBI, NP435 4-speed.

    I offer neither pay, nor quarters, nor food;
    I offer only hunger, thirst, forced marches, battles
    and death.
    Let him who loves his country with his heart,
    and not merely with his lips,
    follow me.

    Offline snowfighter10

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    Re: Air tube check valve replacement
    « Reply #2 on: October 11, 2020, 01:42:45 am »
    I purchased a new check valve from Autozone . It comes with a lifetime warranty. Yay Autozone! With a bushing adapter from 1/2 NPT to 3/8 NPT it will screw right on to the tube.
    1988 W100 SWB, 5.2 TBI, NP435 4-speed.

    I offer neither pay, nor quarters, nor food;
    I offer only hunger, thirst, forced marches, battles
    and death.
    Let him who loves his country with his heart,
    and not merely with his lips,
    follow me.

    Offline snowfighter10

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    Re: Air tube check valve replacement
    « Reply #3 on: October 11, 2020, 01:46:00 am »
     Ive already installed a "new" smog pump from the junkyard. I still have to get a new belt for it. Reinstalled the air injection tube on the motor but without the check valve. Until I get a belt put on I have the tube temporarily capped off with this brass cap.

    1988 W100 SWB, 5.2 TBI, NP435 4-speed.

    I offer neither pay, nor quarters, nor food;
    I offer only hunger, thirst, forced marches, battles
    and death.
    Let him who loves his country with his heart,
    and not merely with his lips,
    follow me.

    Offline ToxicDoc

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    Re: Air tube check valve replacement
    « Reply #4 on: October 11, 2020, 10:09:25 am »
    Nice work. thankfully I don't have emissions testing/inspection in my area.
    '85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

    Offline snowfighter10

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    Re: Air tube check valve replacement
    « Reply #5 on: October 11, 2020, 03:30:29 pm »
     I am keeping the emissions on my truck intact for the registration requirements. A friend told me that if I register my truck as a classic vehicle with limited mileage I will not be required to pass emissions. I have not researched it yet. In the meantime, my smog equipment will be present and functional.
    1988 W100 SWB, 5.2 TBI, NP435 4-speed.

    I offer neither pay, nor quarters, nor food;
    I offer only hunger, thirst, forced marches, battles
    and death.
    Let him who loves his country with his heart,
    and not merely with his lips,
    follow me.

    Offline Elwenil

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    Re: Air tube check valve replacement
    « Reply #6 on: October 11, 2020, 03:42:29 pm »
    I don't think I would try to thread the tubing, it's not thick enough to take a good thread and seal without something to help it.  Might be better in the long run to braze on a brass fitting of the correct size pipe thread and then just thread the valve onto it.
    L.Clemons

    1988 Ramcharger AW450-318EFI-NP435 4 speed-NP205 Transfer Case-Dana 60s-Braden Wormdrive Front Winch

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    Offline ToxicDoc

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    Re: Air tube check valve replacement
    « Reply #7 on: October 11, 2020, 06:03:46 pm »
    It's a low-pressure system. With a little sealer it should hold fine. I'd only worry about whether the tubing will crack, but it doesn't matter now since he's already threaded it.
    '85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

    Offline snowfighter10

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    Re: Air tube check valve replacement
    « Reply #8 on: October 11, 2020, 06:20:06 pm »
    Hahaha! That was a concern when I first set out to do this repair. The tubing is actually small enough that the die did not cut too deeply. It will be fine.
    1988 W100 SWB, 5.2 TBI, NP435 4-speed.

    I offer neither pay, nor quarters, nor food;
    I offer only hunger, thirst, forced marches, battles
    and death.
    Let him who loves his country with his heart,
    and not merely with his lips,
    follow me.

     

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