In reply to Alan Cesar:
You just have to know what each screw does, and get a feel for how they react.
In reply to Alan Cesar:
You just have to know what each screw does, and get a feel for how they react.
Alan Cesar wrote: He'd twist a screw, rev the engine, listen, twist a screw some more, repeat, twist another screw. Within five minutes, the thing was running like a top. Blew my mind.
I saw Jack Roush do this in the pits one time many years back.
Vigo wrote:forget the wideband... you don't need it... normal everyday people were adjusting carbs with vacuum gauges and screwdrivers for 10 decades before anyone figured out how to hook an oxygen sensor to a gauge and marketing them as the latest and greatest tuning tool that you absolutely cannot live without..Where exactly do you think carbs got their reputation? From people using AFR gauges on carbs??No, it came from people NOT using afr meters
, and it came from about a bajillion man hours of labor wasted fumbling around with carb changes that you couldnt determine the side effects, or even MAIN effects of, without wasting a bunch of time and gas driving around in all sorts of conditions to find out what worked and what didnt. There's plenty of stuff you can't set by ear on a carb. For example, this Weber i put on my CRX is supposed to be jetted and set for this engine blah blah blah and yeah, when i installed it i was able to get it to a decent idle AFR 'by ear', and WOT afrs were acceptable as well, but cruise afr was 12-13. Gee, i wonder if that coincides with EVERYONE on the crx forums complaining about poor mpg with a weber? Wanna guess how many of them had a wideband? Mine now cruises at 15:1 and i didnt have to waste a bunch of gas and re-live everyone else's failures to figure it out. You have to be really dang good (which comes from many hours of failure learning how to get good) to old-school your way to the same quality of result as any dweeb with a wideband can get in one day with a jet kit. Even a narrowband is helpful, and you can get a single-wire o2 and weld a nut to your downpipe for like ~$40 total and just read it with a voltmeter if that's what you want. A real wideband is only $150.. And although i didnt get any credit for being the first to point out that it was probably a lean condition regarding the accelerator pump, i will say YOU'RE WELCOME to the OP anyway.
using a vacuum gauge isn't "by ear"... it's a gauge that tells you in real time what that screw you are turning is doing. you can use it to see what the engine is doing at idle, under load, while cruising. think of it as a steampunk diagnostic computer.... and once you get a handle on what the effects of adjusting different things on a carburetor in different ways are and how the other parts of the engine affect it, you can whip a carb into shape in no time.. which, really, is not any different than taking the time to learn what the different sensors and what not do on a fuel injected engine..
novaderrik wrote:Vigo wrote: And although i didnt get any credit for being the first to point out that it was probably a lean condition regarding the accelerator pump, i will say YOU'RE WELCOME to the OP anyway.using a vacuum gauge isn't "by ear"... it's a gauge that tells you in real time what that screw you are turning is doing. you can use it to see what the engine is doing at idle, under load, while cruising. think of it as a steampunk diagnostic computer.... and once you get a handle on what the effects of adjusting different things on a carburetor in different ways are and how the other parts of the engine affect it, you can whip a carb into shape in no time.. which, really, is not any different than taking the time to learn what the different sensors and what not do on a fuel injected engine..
Vigo, THANK YOU for mentioning the possible lean condition. You can tune my carb any day. 
So how about a primer on using a vacuum gauge? I have one that I've used on the engine before- I don't remember why, but it was around the last time I adjusted the valves, so it was probably something related. [shrug]
What am I looking for as it pertains to a carb? Someone mentioned a book a while back in the thread- is there any other recommended reading?
tuna55 wrote:Toyman01 wrote: Be glad it wasn't a Quadrajunk though.
Don't get me wrong, the Q-jet is by far one of my favorite carburetors. It's the only one I know of that will behave like a 200cfm 2 barrel and dump fuel like a 750cfm sewer pipe. If it had been the first one I ever tried to rebuild and tune, I probably would have run screaming.
You really haven't had fun unless you have rebuilt the electronic version though. 
That is the one that made me HATE computer controlled cars for a looooooog time.
you want steady vacuum, and maximum vacuum for a given operating condition... except for WFO, where you want as little vacuum as possible because any vacuum indicates a restriction in the system... and it's cool when you actually get positive manifold pressure under certain conditions at WFO when you don't have a turbo or supercharger ramming air into it.. the only car that i've ever had that happen (positive pressure) was the 355 in my Nova that would snap from 17" of vacuum, to 0, then to about 2lbs positive for a second or so as it hit the torque peak, then back to 0 as it went up thru the rpm band...
vacuum gauges are fun, and can actually make you a better driver and gain you some mileage as you train yourself to be smoother with the throttle because that damn needle moves with every little movement of the pedal as you are cruising down the road..
Toyman01 wrote:tuna55 wrote:Don't get me wrong, the Q-jet is by far one of my favorite carburetors. It's the only one I know of that will behave like a 200cfm 2 barrel and dump fuel like a 750cfm sewer pipe. If it had been the first one I ever tried to rebuild and tune, I probably would have run screaming. You really haven't had fun unless you have rebuilt the electronic version though.Toyman01 wrote: Be glad it wasn't a Quadrajunk though.
you get a feeling of genuine satisfaction and overall manliness when you figure out how to make the secondaries in a quadrajet come in without making the "quadrabog" noise. for some reason, people don't think that they are looking at a fast car when they see a quadrajet on it... but some of us know better..
Agreed, Q-jets are one of the best OEM carbs bar none.
They have the same problems SU's and Webers do. No-one takes the time to learn how they work and tune them properly. Then they blame the part when it's really the monkey with the screwdriver that is the problem.
GM wouldn't have used them for nearly 30 years if they didn't work well.
Heck, Ford even put one on the Super Cobra Jet.
Trans_Maro wrote: Agreed, Q-jets are one of the best OEM carbs bar none. They have the same problems SU's and Webers do. No-one takes the time to learn how they work and tune them properly. Then they blame the part when it's really the monkey with the screwdriver that is the problem. GM wouldn't have used them for nearly 30 years if they didn't work well. Heck, Ford even put one on the Super Cobra Jet.
Dodge put them on trucks in the 80's, too..
if you want to know how to tune a quadrajet, get the book that Edelbrock put in the box with every qjet that they sold when they were making them... the book that came with my 1910 (850 cfm) qjet breaks down what every system does, how to adjust it, and how changes to other systems in the carb- and even the ignition system- will affect it.. i'm sure they'd send you one if you called them, or you can find it online..
You should try tuning one on a draw through, turbocharged, Chevy 250 I6. You will really feel manly when you get it to behave. And this was in the days before WB O2 was readily available. Might have been before it was even invented.
I still regret selling that car. 
Toyman01 wrote: You should try tuning one on a draw through, turbocharged, Chevy 250 I6. You will really feel manly when you get it to behave. And this was in the days before WB O2 was readily available. Might have been before it was even invented.
No problem, I've tuned several on draw-thru turbocharged Pontiac 301's. You really need the enrichment circuit to be ported externally so the primary metering rods will work from manifold pressure instead of throttle plate vacuum.
Shawn
In reply to novaderrik:
I thought Dodge had Carter Thermoquads.
I've never worked with an Edelbrock made Q-jet.
some dodge pickups in the 80's had qjets- i don't know what years or what exact engines and models, but i've seen a few on 360's in 4X4 pickups. they have the Chrysler kickdown linkage, but otherwise look like a Chevy version.
the Edelbrock qjets were just regular quadrajets that were made by Carter for Edelbrock for a few years... some of them were even emissions legal... but they did make the 850cfm version (1910) that was calibrated for use on 350 and 454 engines with the RPM head, cam, and intake package... i have one, and it's been on a few different engines ranging from the stock 200hp 307 in my Nova to the dyno flogged 600hp 455 Olds that the guy i got it from had it on... the book that came with it goes into great detail about how to tune it for different engines and takes a lot of the "scary" out of working on and tuning a quadrajet.
Ma Mopar used the Q-jet after Carter stopped Thermoquad production (and I think all OE carb production) in '86-87. Or sometime around then. The Q-jet was used on the 4bbl trucks that didn't get TBI, and on the police package M-bodies (Diplomat/Gran Fury).
Edlebrock had the Q-jets for several years but dropped them recently. I'm not sure who was manufacturing them for Ed. Weber was making the square bore carbs for them (now Magneti Marelli), but I don't think they did the Q's.
using a vacuum gauge isn't "by ear"... it's a gauge that tells you in real time what that screw you are turning is doing. you can use it to see what the engine is doing at idle, under load, while cruising.
All a vacuum gauge will really tell you is whether an engine is running 'good enough', under high vacuum conditions.
Sound and vacuum gauge are a lot like a narrowband o2 sensor. You'll have most of your resolution in the area around stoichiometric afr where going too far in the lean direction has really obvious results. But there just isn't a whole lot of difference in sound between 14 and 12 and 10:1 when you're doing something a vacuum gauge cant read anyway (which is like half the throttle range), and you're left to tune by 'feel' and maybe with some very tedious and uncomfortably warm plug-reading sessions on the side of the road.
There are probably a LOT of people who consider themselves pretty good with carbs that dont realize how unnecessarily rich their engines run under some conditions, or even that their engines might be going lean under high load/noise conditions (if there isn't something obvious like pinging and speckled plugs to notice).
Like i said, most carb tuning in history has been done to 'good enough' standards, with inaccurate or no AFR monitoring, with relatively poor results, which is why most people can't get good fuel mileage out of modified carb cars even to this day. Lots of people can get a carb to run 'good enough'. But put a wideband on it or test it against a fuel injected version of the same thing, and not many of them would qualify as 'very good'.
In reply to Vigo:
I agree with you on the wideband and carb tuning. However, today for Mez, a vacuum gauge will get him to "good enough" since he has one in his toolbox.
Maybe he can spring for something out of the Innovate catalog later. 
When doing carb work I usually get it running, set the idle speed, set the idle mix with the vacuum gauge, etc, all old-school. Once that's done, then I'll grab the LM1 with the tailpipe adapter and LMA-3 and go log some data for a 21 century tune.
In reply to Vigo: I agree with you on the wideband and carb tuning. However, today for Mez, a vacuum gauge will get him to "good enough" since he has one in his toolbox. Maybe he can spring for something out of the Innovate catalog later. When doing carb work I usually get it running, set the idle speed, set the idle mix with the vacuum gauge, etc, all old-school. Once that's done, then I'll grab the LM1 with the tailpipe adapter and LMA-3 and go log some data for a 21 century tune.
Perfectly reasonable!!
Vigo wrote: Perfectly reasonable!!
That might be the only time in Interweb history that statement has been used.
Big Update
So I had a few hours to work on the truck this weekend. Before making any further adjustments on the carb, I decided to go through all the usual tune-up items: I gapped the spark plugs, and pulled the valve covers to adjust the valves. A few were a little out of range, so it was a good thing I went in there. Interesting note: the factory service manual says to adjust the valves while the engine is running. How the hell are you supposed to do that? I can't even get a wrench on the rocker adjustment bolt because it is rocking away! Never mind all the oil leaking onto the exhaust manifolds... Anyway, I just did it on a hot (not running) engine and had to bump the starter a bunch of times to get all the valves adjusted properly.
After I was satisfied everything was in proper tune, I adjusted the kick-down linkage as previously mentioned in the thread and moved the accelerator pump out one hole, into the center position. I know you guys said to go for the biggest shot, but I wanted to see for myself.
I have two vacuum ports on my carb, and I have NO idea which one is manifold... The first one I tried is the port to the vacuum advance module on the distributor, but I don't think that was the right one because the vacuum was dancing all over the place and didn't respond to throttle the way I expected.The second port had a much smoother vacuum and was doing what I expected based on what I've learned here and in some YouTube videos.
I backed out the idle mix screws a few turns and repeatedly adjusted the idle speed screw until the vacuum was rock steady and holding at 17.5 inches of mercury. The idle sounded really smooth, slower than I've ever gotten it. The engine hardly vibrates at all.
After a shake-down cruise, I was very pleased! The engine has never run so well and really sounds quiet and smooth- almost like a modern engine! I don't have to worry about it dying on deceleration or when coming to a stop as it would in the past. It was still bogging a little from a stop: remember how I said I wanted to see for myself about the accelerator pump? Yeah, you guys were right! I've now moved it to the outermost position for the biggest shot from the accelerator pump. I need to bend the linkage a little bit as it is much better, but could still take a tiny bit more. I need to go a little further with the kick-down linkage still because it will stay in second gear better now, but it still wants to shift too soon.
It wasn't until I'd cleaned everything up and put all the tools away that I saw the small vacuum line coming off of the intake manifold back by the distributor feeding the transmission- I'm going to repeat the vacuum tests soon using that line because I am second guessing everything I did earlier now.
In any event, I really want to say THANKS to everyone for all the help- I feel vastly more comfortable with carburetors now thanks to your help and insight.
Excellent work! Glad you got her running better. Remember, always use your powers for good.
I doubt you'll find any difference from the trans vac port, but it won't hurt to check. If it runs right, it IS right!
I know this is an old thread, but THANK YOU for posting it Mezzanine! Ironically, I have been looking for information on how to properly adjust the "blasted" carb on my '66 Charger (which happens to have a Stromberg WW on top of a 318 Poly). This is a huge inspiration for me since I have been badmouthing that blasted thing for years now. At least I have the confidence now that it is possible to adjust even the Stromberg. But, I have to say, on the accelerator pump adjustment, don't bother bending the linkage unless it's just to take the slop out. Mechanically speaking, shortening that linkage will NOT give you any more shot. It's a set of levers... Moving the attachment point further from the pivot on the initial lever will give a larger throw which will, in turn, give more movement on the second lever and yield a larger shot. If you need more throw, then drill another hole on the second lever that is closer to that pivot point (fulcrum).
Anyway... thank you! Now I just need to sort out the other issues with my Poly [Cyl 6 has all 140psi compression but rarely fires even though it has a verified good spark, it will sometimes stall at stoplights and sometimes run like a raped ape (like today, I had to stand on the brake at one stop light and then had to feather the throttle at the next stop - really annoying!)].
In reply to Mezzanine:
They still commit more acts of witchcraft than turbochargers....so don't feel too bad
novaderrik wrote: some dodge pickups in the 80's had qjets- i don't know what years or what exact engines and models, but i've seen a few on 360's in 4X4 pickups. they have the Chrysler kickdown linkage, but otherwise look like a Chevy version. the Edelbrock qjets were just regular quadrajets that were made by Carter for Edelbrock for a few years... some of them were even emissions legal... but they did make the 850cfm version (1910) that was calibrated for use on 350 and 454 engines with the RPM head, cam, and intake package... i have one, and it's been on a few different engines ranging from the stock 200hp 307 in my Nova to the dyno flogged 600hp 455 Olds that the guy i got it from had it on... the book that came with it goes into great detail about how to tune it for different engines and takes a lot of the "scary" out of working on and tuning a quadrajet.
I have an edelbrock qjet on a 350HO crate engine. great carb.
Someone years ago said 90% of tuning problems blamed on carbs is ignition timing. Get that spot on first.
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