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Old 08-29-2012, 07:26 PM
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reaming quadrajet idel ports ?

so as you all who followed my before about the quadrajet i cleaned up again and such running super lean at idle, you guys said it needed to have the idle ports reamed out ( not the mix screw holes but the brass plugs in the carb base )

since im getting a solid 8 mpg with the suburban now i think this would be a good time to maybe see if i can get the quadrajet fixed and use it as a test??!!

ive drilled out jets for our methanol gokarts and such so as long as i got the correct ream i think i should do okay.

so does anyone know the start of seeing what ream i would use or info as how to do this kinda thing ?

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Old 08-29-2012, 08:36 PM
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Never heard of that! Unless you're talking about the fuel well plugs leaking.
Any mileage gains are acquired by adjusting how deep your metering rods are in your jets. THis is called the APT (adjustable part throttle). Accessible thru a plug on the front top of your carb.
Here's an awesome link for quads.
Quadrajet Info by Lars - Corvette Forum : DigitalCorvettes.com Corvette Forums
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Old 08-29-2012, 08:47 PM
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sooo if my idle is like 17-18 afr and runs like a dieing cat, and mixure screws dont do anything that can be the main jets? ( even after i drilled out the screw ports ? )
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Old 08-29-2012, 09:49 PM
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What do you mean mixture screws don't do anything?
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Old 08-29-2012, 10:47 PM
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my idle

when i got the truck the choke always stayed slightly open, and when i rebuilt it it didnt want to idle until it was warm. so in desperation i junked it and used my carter my uncle gave me, and the truck runs fine now

i have the afr meter on it and it wont idle because its off the charts lean, someone said to drill out the mix screws and i did( very tiny afr change )then someone said u can cut down the needles, so i cut down the needles with my lathe and that still didnt make much of a difference. the idle is like 16.5-17.5 afr and idles like a dieing cat anything past 1200 rpm its nice but 1000 and down its horrible. someone said i need to ream out the ( port plugs ) in the idle circuit. my quadrajet book vaguely talks about it, it shows a guy using a 6 inch ream thats very tiny


but idk if thats the issue or if the jets are wrong, its a 7045583CHEV & GMC Truck, 75-77 Calif.73427029862CP2.79993.6545

carb and has 73 jets/41b needles and the piston spring feels like my 9 inch springs for the eddy carbs


i cant say for sure but it seems like these arent correct
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Old 08-29-2012, 10:51 PM
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the mixture screws have to be backed out soo far they wiggle in the slot and even this makes the idle richer then it should.

food for thought, do some carbs have 2 gaskets under the air horn and not just 1 ? if soo then when my kit came with 2 identical gaskets and i only used 1... could this be a horrible mistake???!!!!
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Old 08-29-2012, 10:57 PM
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nice

my carb is a 75-77 and i have the needles for the pre 75..........


Incorrect Primary Metering Rods
Results in: Poor idle, rich idle, ineffective idle mixture screws, surging at cruise, poor mileage, poor cold-running characteristics, hesitations off idle and/or at cruise, poor manifold vacuum with resultant ancillary problems.
Comments: In addition to seeing incorrectly sized metering rods for the application, I am also seeing carbs with the WRONG rods installed. Pre-75 (up through 74) Q-Jets use metering rods that are approximately 2.47 long overall (total length from the metering tip to the extreme top of the rod). 1975 and newer Q-Jets use rods that are about 2.40 long. The early rods typically also have just a plain number stamped into them (like, 44), or will often have the letter B after the number (like, 44B). The later rods will often have the letter K or M after the number. If an early rod (long rod) is installed in a post-75 carb, the actual shank (body) of the rod will be stuffed down into the jet, resulting in a severe lean condition with associated marginal drivability. Likewise, if a late rod is used in an early carb, there will be virtually no lean-out from the power piston at idle or cruise, and the carb will suffer a severe rich-running condition.
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Old 08-29-2012, 10:59 PM
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Only one gasket.
Where do you have your vac advance on your distributor hooked to?
Can you turn the mixture screws all the way in and it not die?
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Old 08-29-2012, 11:38 PM
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on the dizzy itsself or the line to the carb? i got mine hooked to the one where theres no emissions, because theres nothing on the motor anymore ( its a boat motor )

and yeah it wouldnt even humor the thought of roughly ideling less then 6 turns out

6.5 when i got it
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Old 08-29-2012, 11:39 PM
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im sure having the wrong needles isnt much help either, the passage i read claims its make the motor very lean with little drive-ability
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Old 08-30-2012, 08:13 AM
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I think you've got everything wrong with your carb! Time to slam dunk it into the nearest trash can, get another one, learn all you can from the link and make it run.
You say boat motor. I assume this motor is actually in a boat. Yes or no!!
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Old 08-30-2012, 02:46 PM
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Quote:
Originally Posted by RWENUTS View Post
I think you've got everything wrong with your carb! Time to slam dunk it into the nearest trash can, get another one, learn all you can from the link and make it run.
You say boat motor. I assume this motor is actually in a boat. Yes or no!!

nope, its in my suburban. its a yacht motor =P
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Old 08-31-2012, 07:51 AM
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Whats the spark timing set at?
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Old 08-31-2012, 09:49 PM
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i dont recall

i remember looking at info on here a few months ago and i set the truck to that, i think it like 3500 rpm it was like 8. idle checked out okay too

i probably sound stupid atm but i remember having my laptop out in the garage and doing step by step from a post here on hotrodders.

and the truck runs now, i drove it back n forth to work for like 2 weeks but it has the 1406 on it right now, im getting 8 mpg and everyone says q jets get better mpg, so i figured its worth a try
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Old 09-01-2012, 04:43 AM
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If the spark timing is too low, the idle has to be opened up so far to get it to idle that it pulls fuel from the boosters and not the idle circuit.
You have to remember, you only have so much room for the butterflies to be closed enough to run off the idle circuits. If the timing is set too low then the further the idle speed has to be opened to compensate. When it's off the idle slots in the base of the carb it pulls fuel from the boosters to idle, and this makes the idle mixture screws unresponsive. Thats why I need to know what the base timing is set at and if the vacuum advance is in use.
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