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#1 |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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choke rod length
Hello...
My truck ['72 GMC Custom 1500] has the Quadrajet 4 bbl, with the 'Divorce Choke'. When I first bought truck 30 yrs ago, the rod that goes from the divorce choke coil to carburetor's pull-off was missing. I have still, yet been able to find the right one. Yep, 30 yrs and 3 different rebuilt 4MVs later, I'm still trying to figure out what length rod is needed for the choke to work correctly. I thought about measuring the distance from the top of the rod and the distance between it and the hole it goes through on carburetor's pull-off assembly/linkage. So, I made a rod out of 1/8" rod, 2.700" long...had to start somewhere. With the rod connected to coil and pull-off, when I first started truck, the throttle plate wasn't opening far enough to allow the motor to idle correctly [sounds like lean slow, rough idle]...if I remove the rod and start truck it starts right up, and idles smoothly with the fast idle like I feel it should. So I decided that the rod needed to be longer so when coil started expanding it would open plate enough. By my measurements, I decided that I needed a rod at least .200" longer. I made another rod .200" longer, [2.900", actually about 2.940"], and when I first start truck throttle plate is still not opening far enough to idle and run correctly...it's like the divorce choke coil spring is too strong to allow throttle plate to open enough... do you think that I should make an even longer rod?... I don't want to put a manual choke on this thing [I did that once before on another carburetor because of this problem]. I would like for this choke to be setup correctly...but. I'd appreciate all help, info, and advice. Thanks, Keith |
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#2 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,622
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Re: choke rod length
The choke rod length only determines the rich or lean setting of the choke. As in how long it stays on before it kicks off to a normal idle.
The plate opening is determined by the pull off and linkage. Take a pic of yours so we can trouble shoot it. |
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#3 |
Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,695
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Re: choke rod length
This is off my working mv. Hope this helps.
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#4 |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
yuccales ... I can see from your picture that from end-to-end your rod is around 2-5/8" long...can you give me the length where rod goes through coil spring and the length of other end where clip goes on...thanks, Keith
Last edited by slowboy; 01-26-2017 at 11:17 AM. |
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#5 |
Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,695
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Re: choke rod length
I will take a measurement for you tomorrow. As others have said, Cliffs book on Q-Jets is a must have.
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#6 | |
Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,695
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Re: choke rod length
Quote:
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#7 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: choke rod length
I don't want to be the "RTFM" guy, but I had to do this myself a month or so back and the factory shop manual has the steps you need to bend the rod to the correct length. It tells you to pull it to full stop and then bend rod to adjust, etc...
It got me -very- close. I made one small tweak to my personal preference on it but the book got me to where it'd start, idle, run and drive just fine. So, RTFM :-)
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#8 |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
Thanks for replies guys...
geezer#99 - thanks for picture, all of the rods I have are shorter than yours...maybe I need to make one the length that yours is and try it...it seems that the rich/lean setting is my trouble...if I remove the rod I have completely, and start truck it starts good and idles good on high/fast idle cam, but once I tap gas to get it off high step to second step, plate closes too much and it won't idle right, kinda choking out...if I have rod connected, it will start, but idle drops and choke plate doesn't open far as it should to keep idle up... [trying to add video... https://vimeo.com/201130499 hope video link works]... in video adjusting fast idle made no difference...I feel that the choke rod is keeping choke plate closed too much... yuccales - thanks for picture...I'm going to make a rod the length of yours and try it... davepl - [aka the "RTFM" guy...LOL] ... have read it and aware of what it says about bending rod...kinda no help when you have no rod and trying to find out length of one so you can make one... the pictures show- [1] when first press gas [2] when truck starts [3] when truck is warmed up looks right, but...to get to picture [3] I have to unhook rod until truck warms up, then connect rod back to keep plate open |
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#9 |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
Last edited by slowboy; 01-26-2017 at 11:03 AM. Reason: wrong url first time |
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#10 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,622
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Re: choke rod length
Where'd you get the carb?
I see you're missing the secondary lockout. Could be part of the problem. Do you have headers? |
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#11 | |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
Quote:
And yes truck has headers. |
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#12 | |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: choke rod length
Quote:
Don't forget 2bbl and 4bbl are reversed (one goes up, the other down), so the rods may not interchange, but otherwise it's the same deal.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#13 | |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
Quote:
Plus, my choke coil goes 'up'. |
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#14 | |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: choke rod length
Quote:
I just did it a few months back and it was almost perfect. I used a new coil at that time too because my old one looked bad. I found the choke wound up staying on just a tad longer than I liked so I lengthened the rod a little by bending, and it was spot on. I'd assume you'll need one or two "adjustment" passes on your first couple of cold starts.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#15 | |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
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Re: choke rod length
Quote:
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#16 | |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: choke rod length
Quote:
If that's malfunctioning or leaking maybe it's letting the choke close all the way again? Just a guess. I second the Ruggles book, it's good.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#17 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,622
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Re: choke rod length
And here's some pics and tips to help too Dave.
http://www.corvetteforum.com/forums/...djustment.html |
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#18 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,622
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Re: choke rod length
With headers you have limited heat in the intake crossover. The choke coil takes forever to heat up(if at all).
In post 65 here there's a pic of a secondary lockout arm. Yours is missing in your first pic. You should see it when your choke is full on. If it's missing in the linkage it can cause binding. http://www.hotrodders.com/forum/roch...-190558-5.html |
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#19 | |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
Quote:
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#20 |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
I had really hoped to set this carb up like it came from factory on truck originally.
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#21 | |
Registered User
Join Date: Jun 2010
Location: San Diego Co.
Posts: 1,163
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Re: choke rod length
Quote:
It'll take some disassembly to install. If you don't have it already, invest a few bucks and get Cliff Ruggles' book on Quadra Jet carbs. You'll learn more than you'll ever need about them. Website is Cliffshighperformance.com I used his book for a complete rebuild (not that you need that), and I couldn't be happier with the result. But like I said, this omission is on them... Best of luck
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#22 |
Registered User
Join Date: Jul 2012
Location: Marshall, NC....heart of the Appalachians.....aka, Gods country!!
Posts: 537
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Re: choke rod length
[QUOTE=If you don't have it already, invest a few bucks and get Cliff Ruggles' book on Quadra Jet carbs. You'll learn more than you'll ever need about them. Website is
Cliffshighperformance.com I used his book for a complete rebuild (not that you need that), and I couldn't be happier with the result.[/QUOTE] Best carb $ I ever spent. Got the book and throttle shaft bushing and carb kit from Cliff (little more expensive, but much better quality) spent a weekend reading and rebuilding my Qjet....runs like a new, starts and idles great. Couldn't be happier. |
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#23 |
Custom Sport W/T
Join Date: Nov 2010
Location: Tarpon Springs,Fl & Annapolis,Md. ....................Quaint drinking villages with a fishing problem
Posts: 898
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Re: choke rod length
Slowboy while you are at it you need to get some rat poison on that engine. The rat ate a huge hole in your choke coil cover and pooped on your intake.
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#24 |
Registered User
Join Date: Nov 2010
Location: WINSTON SALEM, NC
Posts: 106
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Re: choke rod length
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#25 | |
Custom Sport W/T
Join Date: Nov 2010
Location: Tarpon Springs,Fl & Annapolis,Md. ....................Quaint drinking villages with a fishing problem
Posts: 898
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Re: choke rod length
Quote:
Good luck, Capt Roger |
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