[Greg Reid]

Ok, I'll try adjusting the pulloff before I get around to driving it again. Makes sense in hindsight. Don't know when I'll have it out again. I will advise results.

[Greg Reid]

Originally Posted by Baron Von Zeppelin

Pull cable / manual chokes have always been my favorite.
With the repo underdash Ram Air cable brackets for 69-70 available, one of those could be used for a choke cable mounting - and have a built-in cool factor.

I haven't used a choke at all in years. This time I wanted my carb rebuilt to work as it should, including the choke plus, I wanted to learn how the auto choke on these carbs is actually supposed to work (Pretty ingenious IMHO).
This particular carb used to require a LOT of cranking if it sat for more than a week. I actually used to pour a shot of gas down the carb and that got real old. I know that's not exactly choke related but thought I'd address all of that stuff during the build. That is, lack of fuel after sitting and bad manners in cold weather for the first 5~6 minutes. Idle speed used to wander all over the place also.
Starts instantly now no matter how long it has sat. Saturday was the second or third time I've driven it this YEAR and it started after about 4 seconds of cranking. I don't know what fixed that as the bowl plugs were not leaking when I tore it down and tested them.

[lust4speed]

I'm too lazy to go look at my carb, but doesn't the vacuum choke pull-off only pull the choke flap open and not affect the fast idle cam? I don't have a problem with running rich, just a little too much fast idling for a few seconds. Yes, the idle drops off the 1,600 cam slot immediately on the first throttle wing and many times doesn't go there unless the car has sat for most of the day. The second cam slot is about 1,200 or so and within 10 to 15 seconds the throttle can be blipped and idle drops all the way down.

[Schurkey]

The fast idle cam is attached to the choke blade lever by a metal-rod linkage. When the choke blade moves, the fast idle cam moves (if there's no pressure on it from the fast-idle screw.)

So the fast idle cam can be synchronized to the choke blade position by bending the linkage rod. When the choke blade is fully closed, the fast idle screw is on the highest step of the fast-idle cam. When the pulloff opens the choke the proper amount, tapping the gas pedal to lift the fast idle screw off the cam, results in the cam rotating to the second-highest step; which it typically a fairly dramatic reduction in idle speed.

If the cam isn't synchronized to the choke position, you may not have proper high-step/second step motion with the choke blade and the choke pulloff adjustment.

1600 and 1200 rpm seems high to me. Even if that's "spec" I bet you could reduce the highest-step speed some, which would also lower the second-step speed.

Does the choke close fully at "room temperature" or has it been adjusted extra-lean?

[Greg Reid]

Someone mentioned this further back but the spec sheet on my carb says that fast idle should be 2800! rpm. I think I have mine set to about 1200~1400.

Anyway, I checked the vac break gap in the choke blade yesterday using a Mighty Vac to pull the dashpot in. It's supposed to be 17/64...about a quarter inch. It's actually a little bit wider than that but what really came to my attention and I think it MAY be my problem.
The '74 carb pulloff uses an 'L' shaped choke lever that is engaged by a link tied to the vacuum break diaphragm. I noticed that occasionally if the L shaped choke lever was about halfway up/down and I increased the vacuum when it's in just the right position, about 2 out of 10 times, the rod will foul the lever as it moves in.
I'm thinking that on a cold day, I shut down just for a couple of minutes and the spring starts tightening up and I start the car, pulling vacuum, it could have just hung up for a second or two until the spring heated up to move the lever down out of the way...That might also explain why when I first bumped it the other day, instead of idle dropping, it actually went UP for a second. Bumped it again and it came down to my normal idle speed.
I bent the lever upward just a hair to better engage the linkage rod and keep the lever from winding up partially in FRONT of the rod... In other words, the rod was trying to skip over the lever and sometimes winds up jamming on top of it perhaps holding idle speed up to the mid fast idle momentarily.
The pic is after I bent it. Didn't think to photograph the problem position... It now has a more positive engagement between the rod and the L lever. Hope I explained that right...
So, it's true that the e-choke cools off faster and causes the idle speed to come up even when the engine may not need it, I think my main problem was this mechanical hangup. I can live with the quick cool down and just wait 30 seconds or so in cold weather to start the car.
Make any possible sense to anyone?

[Sirrotica]

Greg, in the my aforementioned Kent Moore tool set there is a special tool just for bending carb linkages. It can be done with pliers, but much easier to get a rod bent with the tool. The tool is just a T handle with a 1/2 inch main shaft with a slot cut into one end to fit over the linkage, and as you twist it, it will bend or straighten the linkage out. One could easily be fashioned from a 1/2 inch bolt with a slot cut in with a cutoff wheel, and a Tee handle welded to the other end.

The linage binding up will have a detrimental effect on operation of choke functions to be sure. Probably if you hadn't used the Mityvac tool, and just depressed the choke pulloff by hand, you might not have caught it. I hope this eliminates your problem, or at the very least minimizes it. Cliff is right though, when all the carb adjustments are done properly the car will run nearly as well as a FI unit will. The problem is most people don't know how to properly make all the adjustments, or they skip over them when overhauling a carb. How many times have I heard, "I threw a kit in the carb, and it still has problems", mentioned? They didn't do the adjustments as required. This is when Q Jets get blamed for poor drivability, and Holley, or Edelbrock sells them a new carb................LOL

If all the adjustments are done correctly the engine will run flawlessly, but all the adjustments are critical to success. Only doing half of them will give you a half assed overhaul, pointed out to me when I worked in dealerships and was sent for a 2 day carb overhaul school back in the 80s. The schooling I got from GM was usually from excellent instructors that had previously spent time in dealerships on the line, so they knew the drawbacks of working flat rate in a dealership, and would give you any time saving tips, along with the book part of the course.

Doing a complete carb overhaul, as opposed to just soaking a carb and putting new wear parts in is like night and day. I used to earn a lot of easy side money doing carb overhauls as a second source of income because I would do all the adjustments to bring the carb back to new specs, as opposed to just throwing a kit in it, and neglecting the final adjustments.

I also for the most part I wanted the car to be brought to me rather than someone just dropping off a carb and asking for a rebuild. That allowed me to set the mixture screws on the car, and test drive it to check for other problems. Many times the carb is pinpointed as the cause of poor drivability, when it's another problem that is causing it. I know Cliff has a mule engine that he tests his builds on before shipping them out, and he claims that the last step of QC really helped on comebacks in his business.

Just to sum it up, doing all the adjustments is critical in a carb overhaul to make them run as new again. This is one instance of when doing a carb overhaul, you need to read the directions, do the complete set of adjustments, instead of throwing the directions with the specs on them in the circular file. Yes it takes more time, but the results are worth the effort.

[Greg Reid]

Good info Brad. I did a search for that tool and I think I found one or at least something that does the same thing. Interesting. If I were doing this on a regular basis it would be a must have.
Actually, I enjoy the carb work. I've always been a tinkerer and a Q-jet is a tinkerer's dream...lol . Having said that, if you get it set up properly and maintain it properly, it is a joy to behold. Quadrajunk, yeah, right! Key is understanding how the carb works. Cliff's book was a revelation to me in that regard. I tried reading the Doug Roe book years ago and was lost. Cliff's book simplified it and with the great pics identifying every passage by name, and a carb in hand to guide me, the fog lifted. I then went back to Roe book again and it suddenly made sense.
If it doesn't rain too much I'll get it out this weekend for a run around town.

[Cliff R]

Very good points made and excellent information about the relationship between the choke pull-off, fast idle cam, and e-choke, etc.

Two things to add. There are a LOT of different fast idle cams, some having only two "steps", others may have more. For this reason we have to pay attention to the fast idle speed on the highest setting and how big that step actually is. If the choke coil cools down enough to get you up there a really fast and often annoying/embarrassing moderately warm restart may occur. I use a multi-step (pretty sure it has 4 steps on my own carb) cam and get several reductions in engine speed during warm-up if needed.

There are also a LOT of different electric chokes available and being sold for the hot-air and later e-choke carbs. Many will be cheap imported junk, and/or not even designed for the Q-jet in the first place. I know LOTS of folks buy them, as price drives the market no matter what people tell you. These cheap POS e-chokes show up all the time on carbs sent here and if they didn't get broken in shipping a quick "whack" with a hammer and I make certain the customer gets a new one that's going to work like it's supposed to and last for many years. I'm NOT trying to take more money from the customer here, I learned very quickly in this game to NEVER let a carb out of here with a used or cheap replacement E-choke on it. The customer will NOT remember me telling him it should have been replaced when it takes a chit on him after a few weeks or months of use and he's stuck at a car cruise and can't get the engine down off fast idle, then I guzzles down more fuel than the cost of a good choke before he can make it back home! It's also evident they aren't designed for a Q-jet when they "clock" upside down or the terminal isn't in the down position.

WAY back nearly 20 years ago when I went into the parts business I ordered at least a dozen e-choke coils that were available and tested all of them. The one I sell is USA made, clocks correctly and works like it's supposed to. So depending on what you bought and are trying to use the results can be dramatically different and you may have trouble finding the ideal setting(s) for flawless year round operation........FWIW.......Cliff

[Greg Reid]

It definitely crossed my mind that the brand might possibly have something to do with the quick cooldown Cliff. I will have to look and see if I can find a clue to where I got it. Perhaps take a photo of it. I do believe the hanging up was at least part of the problem but that never would have shown up if the spring wasn't pulling to the 'halfway' point after a couple of minutes.
My carb has at least two steps and three if you count dropping all the way down.

By the way, what are your recommendations for setting fast idle? Ballpark, that is.
I'm thinking now that the midway step is kind of important for RPM as the highest step can be dropped down from immediately with a tap of the pedal as the pulloff occurs.
If I set the midway idle high enough so that it doesn't go dead in gear but low enough that it doesn't CLUNK into gear, seems to me that that would be the way to set it....?
Right now, it goes dead on that mid step (if it's stone cold) as soon as I put it in reverse to back out of my garage.

[Greg Reid]

I did find the choke I ordered. Quick Fuel Technology is the maker.
https://www.amazon.com/gp/product/B0...&psc=1&fpw=alm

[Sirrotica]

Cliff, I was hoping you'd chime in here. I know my way around carbs fairly well, but have no where near the experience you have just by shear numbers. Someone that has parlayed one specific model of Rochester carb into a successful business is going to be a wealth of knowledge when it comes to idiosyncrasies of them.

I'm aware that your book has plenty of information in it, but you can't cram every thing you've encountered into a printed version.

The multi stepped fast idle cam makes a lot of sense in giving you more choices as the choke opens and gives a more gradual ramp towards curb idle. Now that you've mentioned it I do recall some cams having more steps on some cams than others.

Of course since you've tested the available offerings of E choke thermostats, you've already done the legwork for us. The adage that cheaper isn't always better, is something that we in the US experience in the cheap offshore offerings we have to choose from everyday. The automotive parts offerings are from perfectly serviceable parts, to crap that isn't even worth going to pick up at the store.

The members here get a bonus of having you check in on our questions daily, and offering your expertise on this board freely. Although there are some persons that question your expertise that sometimes spirals into arguments, rather than a civil debate.

[many birds]

I don’t want hijack this thread, but have a quick question regarding the choke pull off. Is it the same set up for all the early 70’s q-jets? After reading this thread, I tested my pull off, but the choke flap does not crack open at all. Is my link rod incorrect? It goes real close to the L-shaped piece, but never contacts it. The pull off does work and holds the secondary air valve shut and has about 1 sec opening time. It’s a 1973 (7043266) q-jet.

[Schurkey]

The main purpose of the choke pulloff is to yank the choke flap open a little bit as soon as the engine starts. Rochester engineers were clever enough to make it do double-duty, also controlling the secondary air flap. But the main purpose is to pop the choke blade open when the engine starts.

Either your pulloff is way out of adjustment, maybe there's a missing linkage rod, or perhaps there should be a secondary pulloff. Some Q-Jets had two vacuum canisters--one in front, one on the back.

At any rate, SOMETHING is wrong; I bet that engine gargles on gasoline when cold.

[Greg Reid]

Post a pic.
You're not hijacking. It's related directly to the subject matter. In fact, I was going to ask about the different pulloff units and how you know which one is correct for your particular carb. I'm interested in function, not necessarily appearance. The reason being that I have noticed that some of the pulloff units have a shorter plunger than others. In fact, I have two identical '74 carbs and they have different pulloff units on them. One of them I believe is original and lines up ok. On the other one, I had to bend the actual mounting bracket to get it far enough aft to get the vertical portion of the rod behind the choke lever. Otherwise, it would pop over and in front of the rod. Also, even when it was on the correct side of the lever the rod wouldn't allow the choke to fully open. The plunger on the pulloff, being short, kept tension on the choke lever.

[1968GTO421]

For those with an electric choke that they can never get right and think it's the quality of the electric chike, here is Cliff's choke that he mentions in post 28. I need one myself.

https://cliffshighperformance.com/pr...tail-connector

[many birds]

I don’t see a mounting point for a second pull off.

[Cliff R]

Your carb has the wrong choke pull-off AND the wrong link on it.

Although the early plastic pull-offs will fit the bracket, the "throw" is too short for them.

You are using a link designed for the 1975 and later Q-jets, the 73-74 Pontiac and 70-74 Olds use another variety that has a long drop on the front of it to unload the choke on a cold start.

The set-up you are using will not work correctly no matter what you try to adjust.........

[Greg Reid]

Cliff, do you carry the replacement pull off with the long arm and the linkage?

[Cliff R]

Yes, I carry the pull-offs and the link.

There is a second type of link used on some 73-74 Pontiac carbs that is NLA. I'll put up some pics later today of both styles and what is available.....

[Greg Reid]

Good deal. I have a second identical '74 carb, 7044266 I think, that has a damaged link and the wrong pulloff. It's close enough that it works but I had to move the choke lever a bit to clear the link under no vacuum condition with choke engaged. I'd rather have the right parts there.