74 Shortbed
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Secondary metering rod size?
- Thread starter 3504boltmain
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74 Shortbed
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LOL...Send it I can play clobbersaurus on it in a “How to fix a slobberjet” YouTube tutorial
3504boltmain
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Good to see the gang showed up again tonight... One day, I'm going to find y'all some ladies...
Honky Kong jr
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I got one.......you can have her.....
RustyPile
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Aaarrright, it's settled then.. @3504boltmain If you need a shipping box, I can fix you right up with one made especially for carburetors.. We're all friends around here so I can speak for Honky when I say we don't charge one another for our services.. And as for parts, I got them Q-jets stacked up around here like cord wood.. Anything in the way of parts Honky might need he'll let me know and I'll send 'em to him.. That way, 3504boltmain, this carburetor job ain't gonna cost you nuttin..
RustyPile
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Same here
3504boltmain
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Alright, but she might actually be a guy... If that's what you want in return of course.
3504boltmain
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Seriously though, I've re-read this at least five times... Clarify if you could please.
RustyPile
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Same here
RustyPile
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It's all right here in your thread.. Honky is rounding up tools to do a You Tube tutorial on Q-jets.. I talked it over with him and Shortbed and we decided you should send your troublesome carburetor to Honky and let him use it in his tutorial..
On another note: I got something here that needs my personal attention.. I'll be back in a few minutes and all of us can work out the details...
3504boltmain
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So I've got one carburetor... And I'm broke (hence why I work on my own s#$%)... and you've got a chord of Q-jets... and you want me to send mine... I've got a better Idea, Why don't you just throw me all of your Q-jets except leave one for Honkey. I can attempt the impossible trying to figure these things out, and Honkey can get out what causes his ----- tension. You wont have to be called RustyPile if you did all that now would you?
I too need to divert attention.... A Driveshaft needs lubricating again.
RustyPile
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Ok, got my bidnes taken care of..
lol.. Trust me-- Honky has a lot of stuff going on inside his head -- but tension ain't one of 'em..
You're missing the point here.. You see, none of my carburetors need fixin'.. and I shut my carburetor practice down years ago.. You have the broke Q-jet and Honky is just getting started with his practice.. You're the one in need and Honky is perfectly willing to help you out.. By your own admission you're out of money and Honky is wanting to advertise and ........... Well it's a perfect match.. Me and Shortbed are just the facilitators in all this...
stuman
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I lot of people hate the QJ. I like it.
First off, there are many, many adjustments which can be made/messed up.
Hesitation means a couple of things.
First the accelerator pump may not be acting or acting too slowly. There should be two holes to put the linkage in on the accelerator pump. The one closest to the fulcrum will make it act more quickly. I have found the newer kits have pumps which tend to come apart in that the cup comes off of the holder and the pump no longer works. Find one that it not thin blue silicone cup.
Primary metering rods are all the same diameter on the thin end. Jet size determines low vacuum mixture. Different rods have different diameters on the thicker part, and the combination of three factors determines cruise mixture...jet size, rod size and rod depth. Depending on the year, there are two ways to control rod depth. The earlier ones had a soft plug below the fuel filter which had to be drilled out to expose a screw. Later ones have an adjustment which can turned from the top of the carb. The deeper the rods go with vacuum, the leaner the cruise mixture.
Secondary control flap is actually the venturi of the secondaries, and has a few adjustments. The flaps are off center and demanded air flow will pull them open. Their bend is the actual venturi of the secondaries. There is a spring which closes it against air flow which if broken or too loose will cause bogging at WOT by allowing the secondary control flap to be open wider then the air flow requires. There is a flat blade screw on the side near the fulcrum for the control flaps and an allen set screw underneath for this spring, which near the fulcrum/shaft of the secondary control flaps. Secondary metering rods are simple and strictly mechanical based on how far open the control flaps are.
There is a vacuum diaphram which normally is the choke pulloff AND secondary shut down. This will cause the secondaries to taper off as you build manifold vacuum...reach speed. There is also a mechanism to disallow the secondary throttle plates from opening if the choke is not fully open...as in "engine too cold for WOT".
All of these things need to be operational for a QJ to work right, but when they are you have good economy with your foot out of it and ample power when needed.
First off, there are many, many adjustments which can be made/messed up.
Hesitation means a couple of things.
First the accelerator pump may not be acting or acting too slowly. There should be two holes to put the linkage in on the accelerator pump. The one closest to the fulcrum will make it act more quickly. I have found the newer kits have pumps which tend to come apart in that the cup comes off of the holder and the pump no longer works. Find one that it not thin blue silicone cup.
Primary metering rods are all the same diameter on the thin end. Jet size determines low vacuum mixture. Different rods have different diameters on the thicker part, and the combination of three factors determines cruise mixture...jet size, rod size and rod depth. Depending on the year, there are two ways to control rod depth. The earlier ones had a soft plug below the fuel filter which had to be drilled out to expose a screw. Later ones have an adjustment which can turned from the top of the carb. The deeper the rods go with vacuum, the leaner the cruise mixture.
Secondary control flap is actually the venturi of the secondaries, and has a few adjustments. The flaps are off center and demanded air flow will pull them open. Their bend is the actual venturi of the secondaries. There is a spring which closes it against air flow which if broken or too loose will cause bogging at WOT by allowing the secondary control flap to be open wider then the air flow requires. There is a flat blade screw on the side near the fulcrum for the control flaps and an allen set screw underneath for this spring, which near the fulcrum/shaft of the secondary control flaps. Secondary metering rods are simple and strictly mechanical based on how far open the control flaps are.
There is a vacuum diaphram which normally is the choke pulloff AND secondary shut down. This will cause the secondaries to taper off as you build manifold vacuum...reach speed. There is also a mechanism to disallow the secondary throttle plates from opening if the choke is not fully open...as in "engine too cold for WOT".
All of these things need to be operational for a QJ to work right, but when they are you have good economy with your foot out of it and ample power when needed.
DoubleDingo
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Agreed, the Q-Jet is a fine carburetor. And you gave sound direction (advice) on how to adjust it.
DoubleDingo
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@3504boltmain how did this turn out? Did you find a quality kit for the q-jet? Did @RustyPile decide to give you one of the many q-jets he has laying around so you can rebuild it and run it? Or did you find another one to rebuild? There is absolutely nothing wrong with a quadrajet carburetor, but people have their preferences.
