Metering rod charts

Discussion in 'The Venerable Q-Jet' started by matt68gs400, Sep 22, 2017.

  1. matt68gs400

    matt68gs400 Well-Known Member

    IMG_9783.JPG IMG_9793.JPG I was wondering where to find metering rod charts? Not just diameter but diameter at a given length. I started drawing something up for one I had and looking online, I haven't seen much. Thanks!
     
  2. GRNDNL

    GRNDNL Wannabe

    I "think" Doug Roe's Q-Jet book has a chart in it, if you don't have a copy you should pick one up.
    You only really need 3 sets of rods, CC, DA and CK, those are the only ones I've used in the last 20 years.
    I've got a dozen or so if you want to start measuring, I'll have them with me next week.
     
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Here is the Secondary Rod chart from Doug Roe's book. Cliff Ruggles' book has a chart as well.

    SecondaryRodsA.jpg SecondaryRodsB.jpg
     
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  4. matt68gs400

    matt68gs400 Well-Known Member

    Schweeeet! Thanks!
     
  5. matt68gs400

    matt68gs400 Well-Known Member

  6. matt68gs400

    matt68gs400 Well-Known Member

    I have Cliffs book and ordering Dougs.

    Has anyone ever seen anything from the manufacturer?

    In the charts, they have A through G listed. Do they also give a distance from a reference point for these cross sections?
     
  7. BadBrad

    BadBrad Got 4-speed?

    You can use an excel spreadsheet and the charts feature to generate a nice looking profile. Here is the one I made up for my own collection of rods and a few others. upload_2017-9-22_21-8-35.png
     
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  8. matt68gs400

    matt68gs400 Well-Known Member

    Thank you. What worked best for you to make measurements?
     
  9. BadBrad

    BadBrad Got 4-speed?

    I pulled that data directly from Doug Roe's book. My objective was to get a graphic view of the relative fuel enrichment (thicker is leaner) provided by these secondary rods (most of which I acquired from junk yard donors), especially compared to what the factory installed as stock. I also have those jets and primary rods.

    Even with headers, a 118 lc cam, 10-ish to one compression, and a full gonzo timing curve I ultimately found stock or very close to stock fuel metering still provided the best street performance; even less pinging than I was seeing with richer metering. I used to run that top line; three years ago I switched back to the "Buick purch" line.
     
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  10. Cliff R

    Cliff R Well-Known Member

    If you are racing your car and serious about getting the very most out of it at track when tuning then you will need a set of custom machined rods. It's difficult if not near impossible to use the factory rods for this purpose as they will require hanger changes in conjunction with rod changes to keep the fuel curves on par when trying to achieve a more ideal full throttle mixture.

    Tip diameter, length, diameter of the section above the tips and included angle leading to the tips all play a role if fuel delivery once the rods reach full height out of the jet holes.

    For this reason the serious racers we supply carburetors and part for will order a custom set of machined metering rods so they only need to make metering rod changes run to run. These same folks will "map" everything using DA and track data so they can tune prior to making runs and repeat the results w/o a lot of tuning at different races. This is essential because a lot of times you are just not going to get a lot of runs at some outings to nail down the tune.

    It isn't' common knowledge but we have supplied the carburetors and tuning parts for some of the fastest cars in Pure Stock and FAST that use a Q-jet and all of those folks also have a full set of custom machined metering rods for those carburetors. Feedback from them has been excellent, and they tell us that once they figured out the learning curve associated with metering rod changes that in most cases they can install the correct rods for the DA and track conditions and good to go right off the trailer with little or no need to chase the tune all over the place.

    I do the exact same thing here, and can install the correct metering rods for the race I'm at before making a run. My own set of machined rods goes from .030" to .065" in .002 to .003" increment....for example. Even so, I very seldom end up with metering rods smaller than .040" or lager than .055" for the tracks in my area or the weather conditions I'll experience there...........Cliff
     
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  11. matt68gs400

    matt68gs400 Well-Known Member

    FEA90D1B-2361-4BA5-A0DA-15F2C631B895.jpeg Here’s a nice close up of a primary rod I took. With my technology and use of computer aided drafting I’m planning on having some rods remanufactured. A nice fall/winter project.
     
  12. matt68gs400

    matt68gs400 Well-Known Member

    Close up of tip 9761E50E-239A-4205-9B0E-8F061AEE3FDA.jpeg
     

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