I just realized that I own an O2 reading setup I bought years ago to tune the mechanical fuel injection in my BMW 2002tii. It has a sensor holder that clamps to the tailpipe and a small box with readout. What values shoud I be looking for for a well tuned engine 
R Thorpe
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If you're running carbs you're looking for notes of cherry and old leather, with maybe some spice or hints of forrest floor on the finish.
I jest because I don't know the answer other than somewhere between 12.5-14.5 ish. Wait for @DannyP to chime in.
Stoichiometric with gasoline is 14.7:1. Tuning is not as easy as just aiming for that everywhere-- it helps to be rich of that (lower first number) on acceleration and leaner than that on cruise (if you can get away with it).
Heat is also a factor.
Thanks, got the tools might as well take a look. This thing is a gas hog, my 911 got better mileage, and it was a 3.2 with Webbers.
The vast majority of people have the set up pig-rich. Using the A:F gauge to tune is always a good idea.
Here's a how-to.
tl/dnr:
Best A/F ratio at idle is 13.5--14:1
WOT 12.8-13.2:1
Cruise and mid should be in those ranges; a little richer when stomping on it but not below 12, and generally in the 14:1 range when steady-state.
As stan says, you're probably super-rich. Like 10, even 9-ish, which is wrong and stupid and it won't "run cooler" like that either, despite what a plurality of "experts" claim. Just wasting gas, leaving power and throttle response on the table and probably hurting the engine a little too.
I've got the same chore high on my agenda.
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I know I'm running rich. The tail pipes get sooty, instead of that nice gray color they should be.
But, it just runs and sounds best this way.
I've tried all kinds of things to lean it out. Smaller fuel jets (idle, main, idle and main). Larger air jets. Lower settings on the 'mixture' screws (which aren't mixture screws). Lighter on the accelerator pumps.
When I do any of that, it runs like crap and starts popping, or stops responding well. So, I gradually nurse it back to where it runs well and all of the settings end up exactly where they were when I started.
It is a good way to spend a few days, though, feeling like I've just done some righteous guy stuff - the stuff you just have to drink a beer after.
If it weren't for that manly feeling of having once again wrestled the bull and won, it would probably be a complete waste of time.
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What Ed said. Washing your cylinder walls with gasoline is NOT a good thing.
I shoot for 12.5 at WOT(wide open throttle).
What does your wideband say, Mitch?
Also, how much are you reducing your spark timing to compensate for leaning out the fuel mix?
I know @DannyP will chime in here with some actual wisdom.
I don't back off the timing at all with carbs.
But I'll actually know more when it warms up again and I get some road time and tuning time.
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Ed, no wideband, no narrow band, no band of any kind.
The engine builder and Anthony had much experience with builds like mine, so their first guess at vents and jetting was pretty close. I swapped in one size larger idles, left everything else where it was, and it ran pretty well from the start. That was 30,000 miles and six years ago.
It idles, transitions, and pulls well - no dead spots. When warm, it smoothes right out. Never any popping, even when cold or when going down a long hill in gear, foot off the throttle.
Twice a year, at change of season, I'll go around the 'mixture' screws and adjust - but they never need more than half a turn. I think the best thing I did for the carbs was the Magnaspark.
I average 20-23 mpg, but that's maybe because of the 5-speed. On rural roads, I spend more time in 4th than in top gear. On the rare freeway cruise, the mileage can go up to 25-27.
Honestly, if I hooked up a wideband and it told me my numbers are wrong, I'd be reluctant to change anything.
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Everybody sings the praises of the Tomlinson Dellorto and Weber manuals. Your experience may vary, but I've found them to be borderline useless to actually tune a set of duals. They're written with all the precision of a 1979 Car Craft article (they read like a Hot VWs feature). They talk about stuff and give "rule of thumb" settings for mixture screws, air-correction jets, etc., but don't tell you much of anything specific. They have 2 or 3 nice exploded views, but I have an internet connection and can get those views pretty much anywhere, so the books were read once and set aside.
I've read more about this than most people. I think I'm the only man alive that tried to read all 10 bazillion pages of the AF thread over on theSamba. Internet opinions are like belly buttons-- everybody's got one, but some of them are just wrong.
I've had an Innovate wideband for years (purchased before I knew I could get the same thing for 1/4 the money), and have used it to set the idles and mains. I was never very comfortable knowing what to do with the air jets, so I just left them. Carbs are pretty much fancy air-leaks, and I figured I had them as good as they could get without going to EFI.
My car always ran way better than 90% of the other speedsters I've driven, and always returned me at least 25 mpg, no matter what engine I was running. Some engines ran better than others, but there's always the interplay between the actual engine, the ignition curve, and the fuel mixtures.
There are known mechanical combinations that work well (the 2110 with an W120 and 1.25s, the 2332 with an FK8 and 1.4s, etc.). Most of us have one of them, and they're great. But the thing is, no matter what engine is back there-- it can be made way better by tuning it. That's ignition and fuel.
Most of us have a distributor we drop in and set to 30* advance at 3000 RPM. Idle advance is what it is, and we live with the curve. I'm convinced this is 75% of tuning-- getting the ignition curve right, and we just live with whatever we've got for a distributor. 009s are notoriously suboptimal, but most of us don't even have that-- we're trying to do this with a Chinese 009 (or 034) copy. I ran a CB Black Box on the twin-cam motor, and was blown away how much better a stable and customizable ignition curve was. People have no idea. I figured this was about as good as it was going to get.
Then I ran with Danny's Spyder. It was a revelation.
He's got the reputation as a "carb whisperer", and he's made a lot of guy's cars run a lot better by just working with one of the 3 (mechanical, spark, fuel) systems. But I'm convinced that his crank-fire setup was at least 75% of the reason his car ran as good as it did (with carbs, not EFI). His engine pulled hard everywhere, even with worn rings (in 2018). I'm not running his car down at all (far from it), I'm just pointing out that even when the engine was getting tired and needing a rebuild-- it ran well enough that 99.99% of the people out there wouldn't have touched a thing on it.
He played with his ignition curve for years, and optimized it with 50+ different maps. When I drove it last fall, it had a fresh rebuild but still had carbs. There were no holes anywhere-- none. There was no discernable transitions from idles to mains, no hesitation off idle, no stumble on an accelerator stomp. It was as close to perfect as I've ever driven. A 2332 has more outright power, but his car spooled up and took off in a way that most bigger engines I've driven have not. The power the engine has was everywhere. Total output is not the only measure of performance, and not even the one that matters the most.
I came home resolved to go to crank-fire, and I'm deeply "in process". The current plan is to eventually get to EFI, but to set up a Microsquirt system with ignition only to start, then go to injection once I'm completely comfortable with TunerStudio. Baby steps. The Black Box was a gateway drug, but it relies on a distributor pickup. I'm excited to dive into the world of dead accurate and dead stable crank position ignition pulses.
I really do think that we're all starting in the wrong place when we try to tune. Fuel really can't be set up optimally unless spark is worlds better than most people settle for with a fake 009. I'd encourage everybody to get a Black Box at a minimum.
Anyhow, I reread the John Connelly article Ed linked and it helped me get excited about playing with my carbs again once I'm up and rolling with 50% of the Microsquirt (the ignition).
John is a smart guy, and provides way more information than Tomlinson ever did with "the books", but he's not a writer either. It's going to take a season or two to optimize the carbs even with a better ignition. I've got every jet I could possibly need, and have the O2 sensor to get it done.
I don't even think I'm going to put the new engine in the Speedster this year. For once, I think I'm going to stand pat and stick with 'ol trusty (the 2110), and use it for the test-bed for the Microsquirt/crank-fire thing. I can dial in the carbs using John's article as a guide, and see how well I can make this run (and how comfortable I can get with the software) before I introduce a whole different set of variables with an engine needing a proper break-in, etc. The EFI part of the program will be last, and is probably several years away.
Anyway, read the article Ed linked. There's a huge amount of information-- and I can guarantee that if you use half of it, your car will run better than it ever has.
Stan, once again, thanks. I don't do anything special to my carbs. The floats are dead on. The fuel pressure is exactly 3.5 psi. The linkage is also dead on, zero play. After that it's just 4 screws, set to what each cylinder needs, not some arbitrary number.
I would say that the crankfire ignition is the single best thing you can do for these old 4 cylinder lawnmower engines. It makes it start quicker, idle better and smoother. It takes out that crappy, unreliable, and INACCURATE distributor.
Stan writes with an eloquence I'll never have. This post of his should be a sticky somewhere as a must-read to anyone having "carb problems".
I've also read through that Samba thread on AFR, and it certainly took a while. But it took me to an understanding of the why and how. In short, the light came on. John Connelly supplied me with a couple 35PDSIT Solexes(with electric chokes) for a sandrail customer about 8 years ago. I also changed the distributor to an electronic SVDA and ran vacuum line to BOTH carbs. Stacked up a bunch of gaskets under a stock mechanical pump to get 1.5 psi.
I got them installed and running decent but wasn't impressed. It needed other than stock jets. I told him the engine size and exhaust and altitude the rail runs. Dead on jet sizes came in the mail. The man knows things. This rail runs pretty much like any electric-choke-equipped Big-Three single-carbed V8 back in the 70s: 2 pumps and hit the starter. It runs, warms up and idles down. It doesn't bog, spit, sputter or anything else untoward. Eight years later they haven't been touched. Still runs GREAT.
The point of that last is John from aircooled.net has more stuff in his head than a lot of people. He should be listened to when he speaks.
What is a crank fire ignition and where do I get it?
sounds like I need it. My 2110 has the stumble
This is CB Performance's version. There are others.
https://www.cbperformance.com/product-p/2094.htm
An alternative might be the system from 123ignition, but for similar money I would go with a true, crank-fire set-up. Using the 123ignition distributor just can't be as precisely accurate as a 6+" toothed degree wheel.
John's knowledge and willingness to share it is one reason aircooled.net is usually the first place I go to buy stuff, even if the price is a little higher sometimes.
Also, I tend to be less concerned about quality with stuff from there.
@Phisaac posted:Seems pretty complicated. Thank you
Paul ISAAC
Paul: it is!
What you're doing with the CB or other crank-fire kit is grafting on the modern ignition every road car has had for the last 30 years to an engine that wasn't made for that sort of thing—and programming in the spark advance curve your particular engine likes best.
Nothing quick or easy about it.
But it absolutely works and, once done, will likely never need to be touched again. No cap/rotor changes, no points, no condenser and (most likely) no problem ever with the "module" like some people report with the in-distributor Pertronix.
I'm one who believes most of the trouble with the 009 disty can be solved with a good aftermarket unit like the MagnaSpark. Crankfire probably is overkill for most hobby car people. But what Stan says is very true: Danny's car is very, very well set up and that kind of smooth violence is hard to let go of once you've experienced it.
Back O2 ratios, I also agree that John at air-cooled has more real experience with VW engines than almost anyone. I used his guidelines when setting up my air fuel ratio targets and have changed them over time. Here's the thing, every engine is a little bit different in what it wants to run best. Change the compression ratio, running temperature, head/port flow, force induction and the engine will want different. fueling to be in the sweet spot (and/or safe spot).
The BEST way to find it for your engine setup is to get close and then go to a dyno and change fueling while tracking changes to torque/hp. Of course, you'll be listening at all times for engine knock. I've done this many times with my supercharged and turbo engines, but have just depended on my butt-dyno on the 1776 in the speedster .
I've moved a lot leaner than John's guidelines over the last year. I'm running 9:1 compression on Panchitto heads and high test gas in ambient temperatures that range from 70F to 90F. Here's the target air-fuel ratio table that I'm currently using. I don't get any knock with this and the engine definitely likes it better than a richer setup. This is certainly not to knock John, but to give folks a sense of the range of setups that might run best. Always start with a richer setup and move leaner to keep from detonating your pistons or burning your valves, But you guys know that.
