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Integral e-choke/q-jet question
The one issue that I have and do not like with the e-choke/q-jet (with integral choke) combo is that in the type of weather we're experiencing right now...Averaging just about 40~50 degrees or so in the daytime... The choke coil cools down much quicker than the engine and when I start the car after being shut down just a few minutes, the high idle kicks in even though the engine is still fully warmed.
By the time I get out of the parking lot, I can bump it down but it's a hassle switching to neutral as I'm driving and bumping the pedal and I know it's not supposed to be that way. Am I missing something about how to set this up? |
I am no expert but I kinda wish I'd gone with a manual choke for my truck. The electric choke just seems to be hard to get right.
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You could try to tweak choke adjustment a little leaner(clockwise). That will shorten the time the choke is 'on' and may help when it get cooler out. You may be on the edge of having it 'on' too long when full cold.
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you should be able to blip the throttle to get it to kick off of high idle:
Is something askew that prevents you from doing this? |
i agree turning the choke dial counterclockwise a little will pull it off a bit faster & not engage it as soon after shut off. another thing i found when you find the sweet spot for the dial, is to back off the fast idle adjuster screw a bit, if its set to high then it engages the steps on the cam more. some of the factory high idle rpm specs are a little too high IMO & when the weather changes it can make the choke stay on longer or at higher rpms than needed.
im in iowa & deal with this on my e-choke & manual choke cars every season, but have got the dial & flap adjustment in a pretty good spot, backing off the high idle screw about 1/2-1 full turn seems to fix the issue you describe. but im no carb expert, just saying what works for me. |
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The original choke would act no differently than the electric. The choke housing cools down faster than the engine. Maybe you need to convert to FI? |
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I'll figure it out.. Make some adjustments. It's not a big deal. |
Obvious, but make sure it’s not getting a little gummed up also. Seems like every few years I have to spray my linkage as it gets a little gummy and hangs up a little.
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I agree with Greg. Only time it bothers me is leaving a car show or gathering where there is a audience at startup, and despite a lot of fine tuning the choke still cools off enough that it "thinks" a little fast idle is needed. This only seems to happen on my electric choke Quadrajet, and a little less adjustment hurts the initial actual cold start. My band-aid approach is to simply turn the key on and sit there with the choke coil heating up beforehand. Only takes 30 seconds to avoid the embarrassing fast idle start.
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Yeah, I like that idea Mick. I'm glad you chimed in. From reading the previous responses I was beginning to think that I was the only one who ever had that issue. Now I won't have to go to fuel injection.
I did a full rebuild using Cliff's recipe just a few miles ago. Runs great and clean enough to eat off of so nothing's sticking. |
That’s exactly what we do on our kid’s Plymouth. Switched to e-choke when we swapped out his manifold. I wasn’t fond at first, but after learning you could give it your own “input” with a key turn and how long you choose to wait, it’s actually convenient.
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As Dick B has said, the vacuum brake can also be adjusted to minimize the time it is on high idle, many times the only adjustment people make is to turn the choke thermostat to try and solve their choke problems. Making sure the vacuum brake is opening the choke butterfly up upon fire up, and the high idle specs are correct, and within the specifications makes a lot of difference in how an combination acts when it's cold.
Having all three adjustments correct is when the carb will act nearly as well as a FI setup does. No excessive fast idle, and no flat spots or coughing through the carb when trying to accelerate when cold. And no overly rich exhaust from the tailpipes, the kind that makes your eyes burn. It's also important to observe how fast the vacuum brake opens the choke upon startup. A small hole in the diaphragm will make it pull lazily and not open the choke as quickly as it should open, nor as far as it should open. It's best to use a vacuum pump to set the vacuum brake to specifications, and test it's operation. taking the time to set all three adjustments usually will have a much greater effect than just turning the choke thermostat. :2cents: |
The electric choke mechanism has less mass--and therefore cools down faster than a system that depends on intake manifold temperature such as a divorced-choke coil, or even a hot-air choke.
Even so, you should be able to kick from the highest step of the fast-idle cam to the second-highest step INSTANTLY upon starting the engine; and the second-highest step shouldn't have the idle speed so fast as to cause any sort of discomfort. My guess is that you don't have the choke pulloff/vacuum break, the choke-blade position, and the fast idle cam position properly synchronized. With the choke COIL still trying to close the choke, the pulloff/vacuum break should pop the choke blade open far enough that the engine doesn't gargle on gasoline, and with the choke blade forced open by the pulloff/vacuum break--the fast idle cam should rotate to the second-highest step as soon as you touch the gas pedal enough to release pressure on the fast-idle cam. Point being, it's a three-way relationship between pulloff/choke blade/fast idle cam; with the choke coil position and the fast idle screw adjustment making things just a little more complex. https://www.chevelles.com/threads/ad...roach.1131913/ |
The average backyard mechanic usually only adjusts the choke thermostat when they have a problem with the cold running. What Dick B, Shurkey, and myself have tried to convey is that the relationship between all 3 adjustments (vacuum break/choke pulloff, fast idle, and choke thermostat tension) is imperative to proper operation in cold weather.
If the specifications for your particular carb don't work with an electric choke substituted for a heated thermostat, you might have to try substituting the specs from the Q Jet that the electric choke came on from the factory, but I would try the specs from your carb first. The article that Shurkey refers to on the chevelle site is what adjustments you need to make in addition the the choke thermostat tension to have proper operation of a Q jet, or any carb when it's cold. Cliff Ruggles also commonly refers to a properly set up O Jet having mostly the same manners as FI during warm up, and properly adjusted, this is true. If you have a fairly lumpy camshaft it may not have enough vacuum at idle to pull the vacuum break/choke pull off to activate it properly. You would need to put a vacuum gauge on the engine to determine how much vacuum it has and if the reading on a pump such as a mityvac unit would have enough vacuum to operate the unit as required. Although the partially closed choke during warm up should raise the reading to an acceptable level, I would think that you'd have to have a really radical camshaft to lose enough to make the vacuum too low. |
The pulloff is adjusted and I believe it's correctly adjusted. There are no leaks in the diaphragm. The carb runs very, very well. No coughing, no flat spots, great idle. The ONLY issue I have is the one I've described. I'm pretty meticulous with that kind of stuff and even fabricated a reducer to go in the diaphragm line to adjust the pull-off dropout time. I set the gap in the choke valve using a drill bit...can't remember what the specs were now but it was set.
The engine starts cold with high idle just like I want it to, just drops out a little quick when the engine is cold and comes in a little quick when the engine is warm. This is really the essence of my issue. I can look at all of those adjustments again as I think it was summer when I originally set it up. I remember leaning the choke spring just a tad when I first finished everything because I did not like the bit of black smoke when the choke was fully cold. Leaned it out just a bit and got rid of that but now the choke will lean out just a tad colder than I would prefer. Maybe the cold weather requires me to take few minutes to check everything over again...? Again, none of it is a major issue. I rarely drive it in cold weather but I did this past weekend. Otherwise, I may have never noticed it going back to hi idle after being shut down probably 3 minutes tops. It's a 1974 carb by the way and also, just as a point of interest, I have rebuilt 4 of these carbs using Cliff's recipe and quite a few others before I knew to do anything other than disassemble, clean and reassemble so it's not like my very first rodeo on this. I'll take a look at the chevelle site and see if there's anything there that opens my eyes to something I completely did not know about in that dept. |
Greg, as Shurkey has referred to the mass of cast parts of the hot air chokes keep the choke from re-applying as quickly as the electric ones do. You might need to find out what carb the electric thermostat comes on, and use those specs instead of the OEM 74 specs.
The quick cooling off of the electric chokes is why I usually try to use the engine heated chokes on my own cars. I do however remember working on a few of the electric chokes in the dealerships where I worked in the mid 80s and those cars didn't seem to have the common problems associated with electric chokes when doing a conversion from engine heated to electric. That might be attributed to different specs for the choke pull offs, and high idle specs. The magnetic choke angle level gauge (pictured in the chevelle article) was used on most of the later carbs, instead of the drill gauges to set pulloff opening. That could be a problem when converting to the newer specs if you decide this might be the key to your problem. Most people that don't work on carbs for a living wouldn't have that tool at their disposal. I happen to own a Kent Moore carb gauge set of tools, but the average Joe isn't going to have the set. I'm sure you could buy the magnetic choke angle gauge separate though if you googled it. GM/Rochester decided that the choke angle gauge was more accurate than just using drill gauges during the closing years of carburetors. |
Here's a Thexton one that is shipped from GA, same state, for $22:
http://www.2040-parts.com/gm-choke-a...-nos-i1888576/ |
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I have wondered if I just got an off brand e-choke that maybe is a little too sensitive to temp changes. That might explain why it actually heats up faster AND cools down faster than I would like. I cannot for the life of me remember where I got this one. In the past, I have used a NAPA part and I don't recall having this issue back then. |
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. :D :focus: |
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Downside is that it may make the choke-coming-on-when-the-engine-is-still-warm problem worse. I'd try it and see--tighten the choke coil back where it was, adjust the pulloff to pop the choke blade open a hint more. (It won't take much!) Verify fast idle cam is on the second step when the pulloff is opening the choke, and verify fast idle speed |
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.
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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. |
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.
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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? |
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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? https://forums.maxperformanceinc.com...1&d=1607522020 https://forums.maxperformanceinc.com...1&d=1607522056 |
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. :focus: |
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. https://images-na.ssl-images-amazon....DaWbL._AC_.jpg |
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 |
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. |
I did find the choke I ordered. Quick Fuel Technology is the maker.
https://www.amazon.com/gp/product/B0...&psc=1&fpw=alm |
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. ;) |
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.
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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. |
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. |
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 |
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I don’t see a mounting point for a second pull off.
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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......... |
Cliff, do you carry the replacement pull off with the long arm and the linkage?
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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..... |
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.
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I modify the pull offs that I sell if/as needed so they apply and release like they are supposed to....
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Understood Cliff.
In that case, I have already got both working through modifications of my own. I modify the timing of the pulloff with a short length of nylon screw with the head cut off, a small passage drilled lengthwise and inserted into the rubber vacuum line. Open the drilled hole a little at a time to get the 1.5~2 second release. As for the short throw one, I bent the mounting bracket rearward enough to clear...so I guess I'm good. The link is buggered up but it does work. That one is a spare carb anyway. |
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If it works it works. Sounds like a lot of cobbling in lieu of buying the correct parts, but for sure there aren't any rules in this hobby.
Anyhow, below are a couple of pics. First one is an early Olds hot-air converted to E-choke with the more common link that is still available back to the secondaries. The second is a Pontiac 455 Super Duty carburetor with the correct parts used. This set-up is not nearly as common as the first one and that link is NLA far as I know........ |
I misunderstood the intent of your previous post Cliff. To back up, I have two 7044266 carbs. One has the original link and pulloff. It looks like the one in pic #2 that you posted. The spare carb has the same link, slightly buggered up but complete, with a different pulloff with two nipples and a too-short throw.. I 'modified' that one by bending the mount back just enough to clear the lever to compensate the shorter throw.
Personally, I'd prefer to have the proper pulloffs in both of them. Just pm me or email what I need..Looks like either of the ones pictured have the longer throw and looks like either link would work? I'm not hung up on correct appearing. After all, I have a '74 carb on my '68 intake and engine. |
I stock the correct pull-offs and the links as shown in the first pick. The links as used on the Super Duty carb are not available far as I know. I've made a few out of the style that is when I've had to. PITA to bend them into shape but doable with enough effort.......
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