Quadrajet preschool: - Team Camaro Tech
Engine General Engine Discussion.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 21 (permalink) Old Dec 27th, 08, 05:55 PM Thread Starter
Senior Tech
 
Join Date: Dec 2008
Location: earth
Posts: 584
Quadrajet preschool:

Welp, i've decided i'm going to rebuild my quadrajet and learn how they work.

NOTE: This will probably be the most, slow, anal, and to many of you, a highly annoying thread. Please be patient with me as i know next to nothing about carburetors and fuel systems. It's sort of like someone who has to learn to walk again---it will be a slow and arduous (sp?) process. In fact, it would not suprise me if even Liz Taylor knows more about carburetion than me (she's been around). On top of that, she has more money than me. How can i compete?

On the other hand, this thread may be very exciting in that it has never, ever been done before on the net----- an in depth, highly detailed discussion regarding the disection, discussion and analysis of the rochester quadrajet! We are going to make history! And you're welcome to come along.


So the first thing is, i remembered that i had an unused reman dualjet sitting on the shelf (this was when i had a 3.8 buick powered monte carlo) i purchased the carb for learning purposes and while that may sound strange, it really works for me; i have to physically see something in action in order to truly undestand it. My mind is not "mechanical" enough to undestand a concept if someone just explains it. i'm more of a driver than a mechanic.

i figured it would be ideal, for now, to examine this carb for several reasons:
a) Because it has not been used, it doesn't smell so i can do this indoors where it's nice and cozy; It is getting colder here and i don't yet have the practical ability to heat my garage. i am looking towards kerosene.

b) Dualjet is basically a quadrajet minus the two back barrels and this is good enough for now because:

c) i need to learn the very basics. For instance, in order to get the right rebuild kit, i need to know the model number?, jet sizes? etc.

i will eventually (soon) take the quadrajet that needs the rebuild off the engine and move to the garage.


So anyways, first off i noticed that after taking off the choke cover, the choke coil lever (fig. a) is supported by the choke coil and after the coil starts to relax ( i'm assuming the wire to the electric choke is connected to a temp sensor and at a given temp it "tells" the wire to activate the choke?) the choke coil lever will move downwards in the direction of the arrows. This lever is also connected to the actual choke door and as it moves downwards the choke blade also opens to let more air into the carb.



The intermediate choke shaft? (fig.c) is also apparently connected somehow to the choke coil lever and pushes against fast idle cam (fig.d). The fast idle cam is somehow and apparently connected directly to the throttle arm on the other side. As the choke coil relaxes, the intermediate choke shaft will also move fowards/downwards which allows the fast idle cam to move downwards/forwards which, in turn, allows the throttle to be closed slightly more and thus rpm drops as the engine warms up?



My questions at this point are:
and let me preface by stating that by the time i started driving, most cars were electronic fuel injected by then. So, this further contributes to my ignorance. We just turned the key and off we went.


1) i never really paid attention to the step down/tapping the throttle thing with the throttle to get it off high idle; i usually just drive away gently right after starting because i'm not the type that believes in having the engine just chugging away for no apparent reason. i did see my parents (when we had carbed cars) do it, because they apparently believe in "warming up." But even then, i never really paid much attention.
What i'm wondering is, the fast-idle cam, as far as i can see, apparently has nothing pulling on it in the direction of downwards/fowards. So, i'm wondering, is the rpm supposed to drop automatically, or do you always have to tap the throttle to get the rpm's to come down?

2) What is the purpose of turning the choke cover clockwise or counterclockwise?

3) i noticed that the rear vacuum break diaphram (fig.b) pulls a little bit on the choke door whenever the engine is running which allows a little air in because, apparently, even a cold engine needs at least a little air to run. Why didn't rochester simply put a stop screw in for this purpose?

4) The front vacuum break diaphram (fig.e) is not connected to anything. What is it supposed to do?

Last edited by puff puff; Dec 27th, 08 at 06:08 PM. Reason: grammar
puff puff is offline  
Sponsored Links
Advertisement
 
post #2 of 21 (permalink) Old Dec 27th, 08, 06:13 PM
Team Member
 
Join Date: Jun 2000
Location: LaGrange,Il
Posts: 1,026
Re: Quadrajet preschool:

There is a lot of Q-Jet information at http://www.florida4x4.com/tech/quadrajet/index.php

But not so much the detail you are reaching on choke operation.

(1) The fast idle cam releases by gravity on the counterweight item 'D" it is held up initially by the choke coil (2) turning the coil counterclockwise puts more preload on setting the choke harder and going too far might not let it release at all. (4) the vacuum break pulls down on "C" somewhat which allows the fast idle cam to release a notch when the gas pedal is tapped.
(3) there are many different choke arrangements on the quadrajet, some only use one pull-off others like yours have 2 how they interact and are assembled can be very confusing so take lots of pictures.

"How to rebuild and modify Rochester Quadrajet carburetors" by Cliff Ruggles is a must have book. You will also want the factury service manuals, many of the factory sketches and adjustments are included in rebuild kits.

I love the Q-Jet and it is not hard to rebuild. Learning how they work, understanding the systems involved, and the system interactions is a lot of fun.

TTFN
Mat

SSCARGO
Mat Klemp is offline  
post #3 of 21 (permalink) Old Dec 27th, 08, 06:26 PM
DjD
Retired
Dennis
 
DjD's Avatar
 
Join Date: Apr 1999
Location: Fortuna, CA
Posts: 26,485
Garage
Re: Quadrajet preschool:

Some reference material...

http://www.quadrajetcarburetors.com/...tructions.html

http://www.stratagaz.com/Quadrajet/Q...et_7029202.htm

http://buy.ebay.vn/buying/en/display...STER-QUADRAJET

http://www.valvoline.com/carcare/art...cid=5&scccid=5

http://www.digitalcorvettes.com/foru...ad.php?t=88376

...Dennis

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


"Don't take life so serious, you won't get out alive..."
DjD is offline  
 
post #4 of 21 (permalink) Old Dec 27th, 08, 07:32 PM
Gold Lifetime Member
Michael Gekko
 
Join Date: Mar 2006
Location: Wrightsville Beach, NC
Posts: 5,583
Re: Quadrajet preschool:

This will be an interesting thread, thanks for the links posted guys-

1968 Camaro NHRA/IHRA SS/C 'Super Stocker' 396/Jerico
1968 Street/Strip Camaro 350 w/PG
1968 Caprice NHRA/IHRA Stock ELiminator O/SA 327-250 HP



Land of the Free Because of the Brave

It Takes a Long Time to Grow Old Friends
Eleanor's Nemesis is offline  
post #5 of 21 (permalink) Old Dec 28th, 08, 05:50 AM Thread Starter
Senior Tech
 
Join Date: Dec 2008
Location: earth
Posts: 584
Re: Quadrajet preschool:

What is the stock needle size?

The reason i ask is because i'm trying to get a rebuild kit from ruggles performance center and i think they include in their kit an upgraded/upsized needle? But i'm not sure.

2) Any other sources for good rebuild kits?
puff puff is offline  
post #6 of 21 (permalink) Old Dec 28th, 08, 09:21 AM
DjD
Retired
Dennis
 
DjD's Avatar
 
Join Date: Apr 1999
Location: Fortuna, CA
Posts: 26,485
Garage
Re: Quadrajet preschool:

Quote:
Originally Posted by puff puff View Post
Any other sources for good rebuild kits?
Call a couple local parts stores or local carb shop and see if they stock them or can order them. I rebuilt a dual-jet for a friend last spring and he got the kit over the counter. You can also get them from summit or jegs fairly quickly...

...Dennis

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


"Don't take life so serious, you won't get out alive..."
DjD is offline  
post #7 of 21 (permalink) Old Dec 31st, 08, 11:42 AM Thread Starter
Senior Tech
 
Join Date: Dec 2008
Location: earth
Posts: 584
Re: Quadrajet preschool:

Does anyone know what size flare wrench to use to loosen the fuel line from carb?

i've got most of the metric sizes from 13 to 19.
puff puff is offline  
post #8 of 21 (permalink) Old Dec 31st, 08, 12:09 PM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,755
Garage
Re: Quadrajet preschool:

One inch for the filter nut and 9/16 inch for the fuel line.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
post #9 of 21 (permalink) Old Dec 31st, 08, 01:48 PM Thread Starter
Senior Tech
 
Join Date: Dec 2008
Location: earth
Posts: 584
Re: Quadrajet preschool:

So, can i use a 14mm? i will get a 9/16 if i have to, but i'm wondering if i can get by with the 14?
puff puff is offline  
post #10 of 21 (permalink) Old Dec 31st, 08, 01:58 PM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,755
Garage
Re: Quadrajet preschool:

Yep, 25MM for the filter, 14MM for the gas line. However, if too big and too tight, it might round off the corners of the nut. Then ViseGrips® come out.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
post #11 of 21 (permalink) Old Dec 31st, 08, 06:41 PM
Senior Tech
 
Join Date: Dec 2003
Location: Wyoming
Posts: 1,635
Re: Quadrajet preschool:

You might want to pick up a new float while you are there. I can remember at least some of them had the floats made from some kind of foam material and they would saturate. I learned about this on our 1975 Blazer. We laid the old float on a paper towel, covered it to prevent evaporation, and let it set for awhile. Sure enough, it was proven to me that they would soak up some gas.
deerhunter is offline  
post #12 of 21 (permalink) Old Dec 31st, 08, 06:58 PM Thread Starter
Senior Tech
 
Join Date: Dec 2008
Location: earth
Posts: 584
Re: Quadrajet preschool:

i'm planning on doing at least a new float, new needle+seat, and clean out the idle air tubes, new gaskets and filter.

2) i don't think the in-depth, highly detailed discussion that i had hoped for can happen at this time. It would require highly detailed cutaways and illustrations/animations and interactive illustrations/animations. i don't have the time, stomach, illustrative/animation skill, not to mention solid knowledge of how a quadrajet works. However, i feel that the person(s) who do this will make out quite good ($$$). Hopefully that person will be me.
puff puff is offline  
post #13 of 21 (permalink) Old Dec 31st, 08, 07:52 PM
Senior Tech
george
 
Join Date: Sep 2006
Location: detroit
Posts: 2,291
Re: Quadrajet preschool:

Quote:
Originally Posted by puff puff View Post
i'm planning on doing at least a new float, new needle+seat, and clean out the idle air tubes, new gaskets and filter.

2) i don't think the in-depth, highly detailed discussion that i had hoped for can happen at this time. It would require highly detailed cutaways and illustrations/animations and interactive illustrations/animations. i don't have the time, stomach, illustrative/animation skill, not to mention solid knowledge of how a quadrajet works. However, i feel that the person(s) who do this will make out quite good ($$$). Hopefully that person will be me.
By the time you catch up with all the carb gurus already out there..you would be better served investing your time and energy in being the best efi tuner this planet ever saw.Carbs are not going away anytime soon,,but I hear and see more old school guys inquiring about efi on their classics daily.The Quadrajet has been around for decades..most carb guys have a handle on them and will not be pounding down your door for advice any time soon.Most just swap out the intake and stab a tried and true 3310 Holley vac sec on their rides vs playing with the Q-jet.FWIW..I love the Q-jet.Reinventing it would not be how I feed my kids..mapping fuel curves for the young mustang crowd with forced induction and that nos/naz/fast and furious crowd would lead to huge dividends imo.

George
68 Camaro
8-71 blown 461 Rat on E-85
fatblock is offline  
post #14 of 21 (permalink) Old Dec 31st, 08, 08:04 PM Thread Starter
Senior Tech
 
Join Date: Dec 2008
Location: earth
Posts: 584
Re: Quadrajet preschool:

You're probably right; an instructional dvd on EFI would probably be more of guaranteed seller.
puff puff is offline  
post #15 of 21 (permalink) Old Dec 31st, 08, 09:56 PM
Senior Tech
bill
 
Join Date: Jun 2007
Location: parlin,nj
Posts: 1,902
Re: Quadrajet preschool:

as a rochester works. when you hit gas to put choke on it closes. start car the choke pull off will pull off choke. but will not do it unless you hit throttle. it locks on cam. when you hit throttle and electric choke or manifold warmer warms up choke enough than it will idle down. if the engine isnt warm enough it will not let 4 barrels to kick on. once it is warm than it will let 4 barrels to kick in.the bottom part of the 4 barrel will manualy come on but the top part is controlled by vacumn but you can adjust it by screw on side to kick on quicker.quick basics on a quadrajet or any other carb hope it helps you on your way
hereitis67 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome