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Threaded Injectors???

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  • Threaded Injectors???

    I'm getting ready to convert an intake to mulitport and was wondering if threading the injectors and screwing them into the manifold vs installing bungs was a bad idea. It looks like they can go 5/16-18 or 24. They could maybe be pressed into an 1/8 npt, and it's bigger than I'd like but would definitely press into a 1/4 npt. Pressing would probably be good enough but I have access to a Swagelok orbital TIG system. Would the tip withstand a quick weld? Could just be tacked manually? What do you guys think?

    Thanks,
    Kevin

  • #2

    Re: Threaded Injectors???



    http://www.hotrod.com/techarticles/m...uel_injection/
    Last edited by Beagle; June 8th, 2012, 01:31 AM.
    Flying south, with a flock of bird dogs.

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    • #3

      Re: Threaded Injectors???

      I dont know about a weld, those internals are beyond tiny. Are you also transferring more heat to the injector having all that surface area of threads, or is that what the sleeves beagles pic is for?

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      • #4

        Re: Threaded Injectors???

        I would not weld even tack them in, it may weld the inside as a ground. BDS makes them. Plus it will limit you to who's injector you can use. Bungs with a O-Ring
        2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
        First to run in the .90s .80s and .70's in SBN/A
        2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
        2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

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        • #5

          Re: Threaded Injectors???

          I was thinking of removing the plastic cap and threading the very tip of the injector. I would use an o-ring seal above that. The pic Beagle posted is threaded above where I was thinking. I'm trying to eliminate the bungs all together. The heat transfer from the manifold was my primary concern but I don't know if it would really be an issue. I agree welding would be a bad idea but I was just curious.

          Thanks,
          Kevin

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          • #6

            Re: Threaded Injectors???

            There are some on E-bay that thread a bung into the intake, then a typical o-ring injector sits in the bung, and then come with a cap to run a hose too instead of a rail.
            Escaped on a technicality.

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            • #7

              Re: Threaded Injectors???

              Most of the manifolds that Ive worked with dont have much meat above the ports ( not threadable) unless its got "bung pads" (sounds pedantic) cast in- place already. If its got the meat, why not just drill (35/64" w/o runout) and chamfer for the injector? Just curious. Injectors are robust, but welding on them is not one of the things they were designed to deal with (many injectors are mostly plastic anyhow...) and chucking them to thread could be fatal unless youve got a good fixture (dont squeeze em too hard)
              www.FBthrottlebodies.com
              Bruce K Bridges

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              • #8

                Re: Threaded Injectors???

                I have a BBC RPM Air Gap and a SBC Hilborn I want to convert. I'm just being lazy on the Hilborn, but on the Air Gap, I was thinking it would be an easy and attractive way to secure the injectors so I could run individual hard lines instead of a stepped fuel rail.

                Thanks,
                Kevin

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                • #9

                  Re: Threaded Injectors???

                  Stepped rail?
                  Ive done a few BBCs and havnt had to step the rail. I havnt done an airgap though. To avoid cylinder to cylinder variations in fueling, you want to place the tip of the injectors at the same distance from the back of the intake valve on all 8 cylinders, regardless of the runner's steepness (sic) making the top of the injectors a single plane (no step)...For street motors and mostly lower rpm stuff i stick the bungs out to the edge of the manifold. kinda like this
                  Attached Files
                  www.FBthrottlebodies.com
                  Bruce K Bridges

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                  • #10

                    Re: Threaded Injectors???

                    I think I see what you're saying. If I put them all the way out to the edge of the runner the outer injectors will only need to be pulled up out slightly further from the runner wall to match the height of the others. I drilled out the manifold and stuck an injector in it to show you what I'm thinking. This is way too easy. There has to be a reason nobody does it this way. The manifold is 0.32" thick on the thin edge. I haven't been able to get a die to start on the stainless tip but I can't see why it couldn't be done in a lathe.

                    Kevin
                    Attached Files

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                    • #11

                      Re: Threaded Injectors???

                      I have a BBC RPM Air Gap and a SBC Hilborn I want to convert. I'm just being lazy on the Hilborn, but on the Air Gap, I was thinking it would be an easy and attractive way to secure the injectors so I could run individual hard lines instead of a stepped fuel rail.

                      Thanks,
                      Kevin
                      The hilbourne used 1/8" pipe taps on the 90 degree mechanical injectors. If you want to thread them in maybe you can get some brass pipe nipples and cut off the threads off the end and epoxy the injectors into the end of the pipe. The ID of the pipe is close to the 5/16ths you were mentioning, if you are really trying to get them to thread into the manifold. I see what you are getting at, where BK welded in bungs (nice work) you just figure threading them in at that point is pretty simple.
                      Those things fire so many times per second you gotta think any machine work at all is gonna mess with the internal screens or tiny ports the fuel is actually shooting out of. I'm just pretty sure they came up with o rings bungs for alot more reasons, including heat transfer. Think of how many other injectors they could sell if people kept stripping the threads.
                      Last edited by anotheridiot; June 9th, 2012, 01:50 PM.

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                      • #12

                        Re: Threaded Injectors???

                        On the Hilborn I'm going to put them on the inside and make hard lines on the outside for vac. I started milling the BBC intake for bungs. I'm going to weld in solid bungs and then mill them to the same depth.

                        Kevin

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                        • #13

                          Re: Threaded Injectors???

                          Looks good! We make our own bungs in three different heights. The height difference is all below the o-ring land. When we set a manifold up we evaluate the steepest runner condition and pick the size of the bung based on the slope to eliminate o-ring land erosion when you port back the welded-in bung. We find the center of the bung location, drill through there and then concentrically mill a pocket the diameter of the bung down until there is just a small shelf left next to the manifolds "rail" (the rest being a hole). Weld the bung in then port it back. Make sure to leave room for any additional porting if you are going that way vis a vis additional bung height. A picture would work better here, but I dont have anything thats unported to show...
                          www.FBthrottlebodies.com
                          Bruce K Bridges

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