General Category > Quadrajet Carb Talk and Tips

Sec Hanger Height

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Cliff Ruggles:
The hanger height controls the fattest portion of the rod in the jet (orifice) at the initial onset of the secondaries.  Since the secondary cam raises all hangers the same amount, it also controls how much of the tip is in the jet at full lift.  These facts are pretty obvious.  What isn't obvious, is that different metering rods have different dimensions for their entire length, and produce different fuel curves as they lift out of the jets.

The length of the tips, and diameter, combined with how far they are out of the jets, will have final control of the fuel flow once they reach maximum height.

It is actually possible to go to a smaller tip rod, and lean up the fuel curve vs a longer tip rod that exposes more of the jet opening (based soley on hanger height).

For most applications, it is best to start out with a lower hanger (higher letter).  I made a gauge years ago from a peice of flat stock, by drilling different holes in it, corresponding to the "B" hanger and up to "P".   I don't search in vane these days for various different hangers, I just bent the arms to get them even and where I want them on the scale.

I use DA or CE metering rods for most builds, and set the hanger height low for initial testing, then bend the hanger if/as needed for best results during a running test.....Cliff

von:
I guess I'm still confused as to hanger height versus hanger letter code. Either that or the chart I saw in a Doug Roe book is wrong. I'm assuming by "higher letter" you mean a D is higher than an F, correct? Or the other way around?  Per the chart I saw, a D hanger has a centerline of rod hole to bottom of hanger attaching flange spec dimension of .530 and an F hanger is .540. That would mean the F hanger would put the rods lower into the oriface at the same air valve opening and therefore tend to be leaner with the same rods as a D hanger, correct? In your book second recipe you recommend a G or higher hanger. I took it to mean G,F,E, etc. Is that correct?

omaha:
I think you are correct. Just like the B hanger is .520
                                                  the P hanger is .590
                                          I could see the confusement.
    since you are measuring from the top down, it actually means that the rods are hung higher in comparison 
                                         to the jet with the B hanger at .520 than the P hanger at .590.                   
                                                                                                                                                                                                            [In the alphabet you could say that the P letter is higher than the B letter.]                             
                                        Not the case with the rod hanger letter designations.                                               
                            The lower letters in the alphabet actually HANG the rods HIGHER in the jets.
             If you look at the summit site, it lists the hangers they sell {seperately I guess} as B, G, K, and P.
              Where can other hangers be obtained?  Would  a person actually need more of a selection than these for fine tuning?  I wouldn't think so seeing as you can bend them to suit your needs. I know rods a able to be modified also.    This is all very enlightening info as I have not put much research into the secondary side yet.

von:
How can the lower letters in the alphabet hang the rods higher in the jet then higher letters when the dimension is more from the hole to the mounting surface? The greater dimension places the hole and therefore the rod closer to the jet.

Cliff Ruggles:
Confusing stuff, isn't it?

I really don't pay much attention to hanger height here.  Decades ago I made a gauge from a peice of flat steel the same width as the part in the q-jet that holds the hanger.

Using a "B" and then an "P" hanger, I drilled a small hole at each point thru the flat stock.  I use this to compare different hangers, and custom bend them if/as needed. 

It's interesting to find that most factory hangers to NOT hold the rods exactly even, being a mass produced part, and often they get bent during rebulding, especially when the rebuilder bolts down the airhorn with the hanger and rods still in it!

What I do pay close attention to is the metering rod.  Rods with rich tapers and long tip delivery more fuel everyplace than those with fat sections and short fat tips.  As a general rule of thumb, rich tapered rods require a lower height in the jets, all else being equal.  Also, the better we set up the POE system, as mentioned in our book, the lower the hanger will be required.......Cliff

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