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Old 08-31-2012, 09:05 PM
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quadrajet idle tubes

i called my local carb shop and they said my issue for the qjet wasnt the metering rod but the idle tubes, he was telling me theres a certain " sound " they make when u blow air through them.

he offered to blow the tubes for me for free and if they were clogged he'd tell me, but the way he talked to me on the phone i was kinda hoping to never meet him.


i pulled mine out ( they looked somewhat tampered with or like if someone scratched the surface of one ) and after looking up replacement tubes i see that they are .035 tubes.

Idle Pickup Tubes - Rochester Quadrajet Carburetor Parts


mine i can slip a .039 bit in the stepped end and a .052 bit inside the opened end ( what u see in the carb base>under what u put the drywall screw in to remove them)

someone mentioned that theres .037 tubes but idk


so can anyone explain what i have versus what i now need being i removed them and need new ones ?

id prefer not to meet this gentleman lol

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Old 08-31-2012, 09:17 PM
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I got the most complete Quadrajet Rebuild kit I could from Cliff Ruggles, and it just replaced my stock idle tubes. From what I recall. the key point in his book was to make sure the tubes are not plugged. I don't remember much discussion about using a different sized tube.

I don't have Ruggles's book handy, but can try to find my copy if you don't get any better answers to your question.

Bruce
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Old 08-31-2012, 09:32 PM
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well

if thats the case then i might just get another set of the tubes. i need new mixture screws anyway.
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Old 08-31-2012, 09:41 PM
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Quote:
Originally Posted by 75gmck25 View Post
I got the most complete Quadrajet Rebuild kit I could from Cliff Ruggles, and it just replaced my stock idle tubes. From what I recall. the key point in his book was to make sure the tubes are not plugged. I don't remember much discussion about using a different sized tube.

I don't have Ruggles's book handy, but can try to find my copy if you don't get any better answers to your question.

Bruce

did the book talk about cleaning those ports where the tubes came out of ?

the guy i talked to said ( just because air and carb cleaner goes through the idle tubes that doesnt mean theyre cleared out, they become "corrosantifyed" and plugged up)

also how did u install the new tubes ???
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Old 08-31-2012, 10:24 PM
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quadrajet carb

I been following your post about your carburetor. I see now you have taken it to a shop. If your going to pay someone to service your qjet why not send it to a professional. Here is a good place to check into. Give them a call, have it professionally rebuilt. SMI Carburetor Other Services Rebuilding & Modifying Rochester Quadrajet SMI- Sean Murphy Induction
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Old 08-31-2012, 10:27 PM
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ok

i havent taken it to a shop yett and dont plan to unless i have to, and even then id just find the guy who did our boat carb.

thankyou for the link
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Old 09-01-2012, 06:50 AM
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According to Ruggles' book, "the restriction in the idle tubes varies greatly in different applications", so size does matter. However, it is also matched to the other idle passages, so just changing to larger tubes may not be a good idea.

The trapped dirt is under the idle tubes, so once you get them out it should be easy to clean out the area. You can also use a stiff wire to break loose any gunk that is trapped at the bottom.

If you got the tubes out, that is the hard part. You have to use a small drill bit or punch to drive the idle tube down, and then use a drywall screw to engage the outer collar and pull it out. Once the collar is out, the tube should just drop out when you turn the carb over.

To put in the new tubes I just pushed the tube and collar as far down as it would go, and then used a small piece of wood to drive it down until it was level with the carb. Take it slow, because you want the tube straight and you don't want to flare the top end by hitting it too hard.

Bruce
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Old 09-01-2012, 07:17 AM
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wow thankyou !

Quote:
Originally Posted by 75gmck25 View Post
According to Ruggles' book, "the restriction in the idle tubes varies greatly in different applications", so size does matter. However, it is also matched to the other idle passages, so just changing to larger tubes may not be a good idea.

The trapped dirt is under the idle tubes, so once you get them out it should be easy to clean out the area. You can also use a stiff wire to break loose any gunk that is trapped at the bottom.

If you got the tubes out, that is the hard part. You have to use a small drill bit or punch to drive the idle tube down, and then use a drywall screw to engage the outer collar and pull it out. Once the collar is out, the tube should just drop out when you turn the carb over.

To put in the new tubes I just pushed the tube and collar as far down as it would go, and then used a small piece of wood to drive it down until it was level with the carb. Take it slow, because you want the tube straight and you don't want to flare the top end by hitting it too hard.

Bruce
thankyou for the details! since i was stupid and pulled the tubes while i had the carb apart to make throttleshaft bushings, for all i know it was the throttle shaft all along, and i really think that since i see no grime/grit/$h!t down where those tubes were. after making my bushings i cant believe how the shaft doesnt wobble, so im going to believe that the 1/16 slop in the throttle shaft was like leaving the vac advance unplugged =[
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Old 09-01-2012, 07:28 AM
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Quote:
Originally Posted by 75gmck25 View Post
According to Ruggles' book, "the restriction in the idle tubes varies greatly in different applications", so size does matter. However, it is also matched to the other idle passages, so just changing to larger tubes may not be a good idea.

The trapped dirt is under the idle tubes, so once you get them out it should be easy to clean out the area. You can also use a stiff wire to break loose any gunk that is trapped at the bottom.

If you got the tubes out, that is the hard part. You have to use a small drill bit or punch to drive the idle tube down, and then use a drywall screw to engage the outer collar and pull it out. Once the collar is out, the tube should just drop out when you turn the carb over.

To put in the new tubes I just pushed the tube and collar as far down as it would go, and then used a small piece of wood to drive it down until it was level with the carb. Take it slow, because you want the tube straight and you don't want to flare the top end by hitting it too hard.

Bruce

so did you get a set of tubes like these ?
Idle Pickup Tubes - Rochester Quadrajet Carburetor Parts

they claim to be original specs and such. a set of those and mixture screws im only out $20 and i might buy a calibration kit from them while im at it
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Old 09-01-2012, 08:40 AM
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Have to agree, Cliff Ruggles is the man you want to talk to about your Q-Jet. Cliff's High Performance, Mt. Vernon, Ohio.

His kits include the tubes. He knows which carbs need the larger ones (emmissions related). Not cheap, but absolutely the most complete "kit" available. He and I disagree on floats, though. I prefer brass, as "Qaudra-Flood" is an earned nickname, based on "heavy" fiber floats. Many a rebuilt Q-Jet has been scrapped because it still would "flood" after the rebuild, when a new float would have cured it. Brass floats don't get "heavy" unless they leak. Borg Warner, NAPA and many others still offer brass for most carb numbers.

Though more "Pontiac-related", his book is among the most comprehensive studies of Q-Jet. Cliff is a Pontiac guy, and is responsible for the carbs on some of the quickest NHRA SS Pontiacs including the Angeles car (9.0s '68 Firebird, C/SS/A). Virtually everything applies to all Q-Jets, regardless of original brand. SA Designs is the publisher.

Jim
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Old 09-02-2012, 03:39 AM
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Quote:
Originally Posted by LEROYDOZOIS View Post
did the book talk about cleaning those ports where the tubes came out of ?

the guy i talked to said ( just because air and carb cleaner goes through the idle tubes that doesnt mean theyre cleared out, they become "corrosantifyed" and plugged up)

also how did u install the new tubes ???
The idle circuit is about the most important thing to get right on a Q-jet when used on a performance engine. Depending on the original application, the idle circuit can be very restrictive and w/o proper tuning, the idle and off idle response will always be a problem.

The guy is at least partly right about the amount or sound of the air blown through the tubes. But unless you have done this, forget it- about the best you can hope for is to verify that there is an equal amount of flow through both tubes. If one is obviously more restricted than the other, well, you have a problem. Best bet is to just remove them and clean and reinstall. If the tubes only need slight opening up (the small, bottom end is the "working" orifice, you can use a small numbered drill bit and a pin vice to open them up.

A bit of info on the Q-jet in general and removing the tubes in particular can be found here. Ruggles' book is said to be the schitz among the Q-jet books available. Roe's book is often mentioned as well. They are listed in the article linked to above.

Good luck.
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Old 09-02-2012, 06:56 AM
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My rebuild kit came with a standard replacement set of idle tubes like you have in the picture. I also asked them to include mixture screws that had a standard screw head instead of the D-shaped head on my original screws.

Its still hard to get to my idle screws because they originally had anti-tamper caps over them. The previous owner ground the caps off, but the screws are still back under the overhang of the carb flange. The screwdriver has to be almost exactly horizontal to reach the screws, and its hard to see the screw heads. At that angle my hands also get close to the fan and shroud.

Bruce
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Old 09-02-2012, 07:54 AM
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coool

well i have a new set on the way along with the mixture screws. i dont have too hard of a time with turning them but it is a pain too, something about my hands and flex fans just dont get along =]
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Old 09-03-2012, 08:34 PM
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Quote:
Originally Posted by LEROYDOZOIS View Post
well i have a new set on the way along with the mixture screws. i dont have too hard of a time with turning them but it is a pain too, something about my hands and flex fans just dont get along =]
If the idle screws have the "double-D" or hex-shaped heads, slot them for a straight blade screwdriver before installing them- OR- get an idle screw adjustment screwdriver w/the different bits that include the Q-jet screw heads. The tool also has the added benefit of a flexible shaft to allow you to keep away from the fan and belts.


Double-D screw


Idle mixture adjustment tool
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