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

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.

Re: choke rod length
 

This is off my working mv. Hope this helps.

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 :-)

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

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

Re: choke rod length
 

this video is once truck is warmed up and I replaced choke rod...

https://vimeo.com/201137825

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?

Re: choke rod length
 

I disagree, I think you could make one out of a coat hanger with the steps in the manual, but to each their own! The picture below should do it.

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.

Re: choke rod length
 

And here's some pics and tips to help too Dave.
http://www.corvetteforum.com/forums/...djustment.html

Re: choke rod length
 

So Dave...you're saying as long as the bottom of rod is all the way down on a cold choke coil spring, and the top of the rod is at the bottom of hole when choke plate is completely closed, that's the length of rod that's needed...measure by that distance to make one.
Plus, my choke coil goes 'up'.

Re: choke rod length
 

I bought the carb last month from Guaranteed Carburetors out of Florida...and I don't know what you mean by missing the secondary lockout. Where's that suppose to be?
And yes truck has headers.

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

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. :mm:

Re: choke rod length
 

lol...I get the feeling that you don't have a quadrajet on yours:lol:

Re: choke rod length
 

I hadn't noticed that it wasn't on there...do you know of any reason that the company I bought carb from would not put secondary lockout on carb besides a possible oversight?...

Re: choke rod length
 

I had really hoped to set this carb up like it came from factory on truck originally.
:waah:

Re: choke rod length
 

Yes I have a Quadrajet on mine and would not have it any other way. Try to come up with an original cover for the choke coil. You can make an aluminum plate that will cover the hole and drill a hole in it so you can slide it over the rod and just let it lay on top of the cover. The heat loss from the cover that you have now is likely causing a good portion of your problem especially in cold weather which is when the choke is needed the most.
Good luck, Capt Roger

Re: choke rod length
 

Covers are available.
http://quadrajetparts.com/quadrajet-...-c-128_23.html

Re: choke rod length
 

With a name like "Guaranteed Carburetors" they should have NO problems taking careof that for you...on their dime. But that lock-out should definitely be there. It's part of that choke mechanism, and prevents the secondaries from opening before the engine is warmed up...Even if you floor it, they are physically blocked from opening up. As your choke moves fully open with heat, the lock-out rotates out of the way...

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

Re: choke rod length
 

I don't want to paraphrase the manual without having it in hand, but that's the basics of it. You make a rod like an L I think, with just the part in the choke coil. Hold that against the stop and then bend the rod in the right place to get the basic shape, then bend the top L to go into the carb. Adjust the rod length by bending so that it winds up the length advised in the manual.

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.

Re: choke rod length
 

thanks will try...just not sure what keeps the choke from staying on at first start...doesn't stay on but a few seconds then the choke plate seems to close back choking motor out

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.

Re: choke rod length
 

Your choke rod might be binding I have a couple of these quadrajet with divorced choke and the top hook points to the outside of the truck. Snap ring on the outside. It gives a more straight up and down shot Here is one I put on a performer rpm with a square to spreadbore adapter and it works just like it should. I tapped a hole to bolt the coil housing down and a dimple for the nub on the bottom

Re: choke rod length
 

Pic. Factory one beside longer one I made. This has been configured like this for 8 years and 30k miles