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Oil Pressure Sender Mystery

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Bowtiek10, Feb 16, 2017.

  1. Bowtiek10

    Bowtiek10 Registered Member Premium Member

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    This story begins with a 400 sbc that I had the local machinist put together about a year ago for my project k10. It was given to me from a family friend. Before I sent it to the machine shop, I stripped it bare. Fast forward a year, its a clean new 406 with all the bells and whistles. Here I am putting it into my k10, where this week I was trying to install some mechanical gauges. When I got around to the oil pressure gauge, the block wasn't tapped for 1/8in or 1/4in. Upon further inspection, the pitch is very tight, almost metric.
    [​IMG]
    What I have concluded is that the pitch is somewhere around 3/16 or whatever its equivalent may be. The best part of this is I went to napa with the sender and they had never seen that bushing deal before. The people at napa and myself thought it was maybe HeliCoil, but the pitch is far off, and they couldn't find what the pitch was either. My theory is that the people that had it before my friend must have stripped the threads, tapped it with god knows what, and used this bushing to fill that in.
    [​IMG] [​IMG]
    My theory doesn't amount to much because I still have to find a way to get the hole filled and have working gauges. Here are the options I have come up with:

    1.) Find a way to tap the whole to 1/4in, without allowing shavings to enter, and adapt the 1/4 to 1/8
    2.) Find a way to remove the bushing nonsense and put it on the mechanical gauge fitting
    3.) Find a replacement for the bushing (If they did it how long ago, why can't I find a way?)

    Any thoughts on this? Have any of you seen this kind of thing before? I'm dumbfounded and after about a week straight of searching I haven't come up with anything useful
     
  2. blazer74

    blazer74 Member Premium Member

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    Helicoil insert for stripped threads.
     
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  3. sweetk30

    sweetk30 professional hooker Premium Member

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    tape / dope it up reinstall and forget about it .

    use the port just above the oil filter boss.
     
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  4. diesel4me

    diesel4me 1 ton status Premium Member

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    I doubt anyone could heli-coil that port with the engine in the truck..
    I'd tend to think that "bushing" was just that--an adapter or threaded bushing that had busted off in the engine..

    I haven't seen any metric threaded oil sender ports,but maybe GM did use them ,they had metric fittings on other things like air pump "flute pipes" ..

    I cant see the bottom of that port,it might be it has a flare seat and they used metal brake line tubing instead of a sending unit for a mechanical oil pressure gauge..those had threads like 3/8x24 or 7/16x20 ...but every Chevy motor I've had was 1/8" NPT x 27 threads at the oil sender port..

    You could re-tap it by greasing the tap up good,the grease will keep the chips from migrating into the oil passage...then use a shop vac to suck up the grease and chips..I've done quite a few spark plug heli-coils that way with no problems..
     
  5. Bowtiek10

    Bowtiek10 Registered Member Premium Member

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    I think I'm going to head in this direction
     
  6. Bowtiek10

    Bowtiek10 Registered Member Premium Member

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    Nevertheless, thank you for everybody helping out with advice
     

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