Weber vs Asian (1 Viewer)

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Weber vs Aisin

I have owned several cruisers over the years- been driving one daily for the last eightteen years. Jim C has rebuilt several carbs for me over the years and I have never had a complaint about any of the rebuilds- all worked perfectly. I've had Jim C rebuilds on both street trucks and my wheeling vehicles and never had a complaint- not on steep uphill or downhill trails nor on any off camber trails. Never had my engine stall from anything other than a driver error, either. An Aisin carb in good working order is as good as I would ever want or need on an F or 2F engine. My winter driver last year and this year is an 86 FJ60 whose Aisin carb looks like it was never touched. It fires up in all weather and runs great.

Having said all that I have owned two cruisers with Weber carbs, and both worked well. The carb on my current trail truck is a Weber and works well in all situations. The Weber carbs I've had have been either new or almost new so that fact needs tio be considered.

One bad feature of the Webers is the cable throttel setup. Over the years I've seen several Weber-equipped trucks break their throttle cable on the trail. The mechanical linkage of land cruisers with Aisin carbs is pretty much idiot-proof and fail safe especially if the keep the pivot points lubed.

Gas mileage is bad no matter what carb I've run in all sorts of carbureted land cruisers. Currently I own and drive a 76 FJ40 (Weber) 77 FJ55 (Aussie with stock Aisin) and my 60. Best I ever got was 14MPG in my 60, and that was on a 55 MPH highway only trip.

I would take a Jim-C rebuilt carb over any Weber if I had the choice. I've been told Mark Algazy also does a good job on Aisin rebuilds although I've never run one of Mark's carbs. My opinion. Gary S
 
+ 1 on Jim C's abilities to rebuild / Desmog Aisin carbs.

Im seeing 14+ Mpg on my FJ60 with a Jim C desmog Aisin and recurved Dizzy on 33's.

(with a fuel vapor leak back around the tank i've yet to troubleshoot- should only get better when i fix that)
 
Last edited:
FYI placed this thread in FAQ.
 
FJ40Jim said:
"I don't see why someone with mechanical abilities would choose a weber carb over an Aisan. Sure you have to spend a half hour to desmog it, but it is fully tunable for any bolt on acc: header, dizzy, camshaft, high flow exhaust, desmog,or even changes in altitude."

^Fixed it for you^

Weber doesn't make a carb to fit a Cruiser engine. They focus more on the small car and performance market. The Aisan carb is big at the top end (~60% bigger than the common weber swap), but has a small primary barrel for low speed operation. It is designed for the Cruiser engine and it's unusual demands.

From an old post:
Stock FJ60 carb is almost the biggest that is readily available. 75-76 USA carb is biggest CFM available, around 425.

The weber 38/38 that is commonly sold as an upgrade has 38/38 throttles and 26/26 venturis.



By comparison Aisan 38/40 has 31/35 venturis.

Aisan throttle area: 23.90cm^2
Weber throttle area: 22.68cm^2
Aisan is 5% bigger.

The limiting factor to airflow through a carb has to be the venturi. For the carb to work right, there must be a significant delta P right at the venturi, a greater change than anywhere else in the induction system.

Cross sectional flow area at the venturi:
Aisan: 17.17cm^2
Weber: 10.62cm^2
Aisan has 61% more CSA in the critical venturi area.
Click to expand...

thanks for correcting my statement, and all the info you gave on this topic, so far with the Asian carb i havent had much problems , at cold start i have to pump it alot to get it to start, on your rebuilds do you change the float level for ex-stream wheeling,
or leave it at the specified adjustment,
 
There is no such thing as a perfectly tuned, right out of the box, after market carb, period. It doesn't matter what engine you're working on nor does it matter what brand of carb you choose. Some knowlege of how to tune a carb will be required no matter what. When I ran a Weber on my 2F (when I had a 2F), it bolted up and ran better than it had in years, but it wasn't perfect. Only after some tinkering did it really get to running well. A distributor recurve should be considered essential with either a desmog or a Weber if you want all the potential you can get out of it. I have yet to meet anybody who ran a Weber and knew how to tune a carb that didn't like them. There are plenty of people who don't know how to tune one and guess what? They hate them as they would any after market carb. The same argument used to be hashed out over and over with Rochester four-barrel carbs vs. whatever, especially Holleys. The Rochesters were incredibly tuneable, could tolerate virtually any angle yet because they required more calculation (area of the jet orifice minus the area of the metering rod at low vac and at high vac for starters) and more knowlege to tune them they were widely disliked. FI is not a bolt on affair either, it is now software instead of jets and metering rods, but the affect is the same.
 
I have just installed a 38/38 weber on my 87 2f motor and have found it to be running rich as well. What jetting adjustment do you suggest?
 
zonayota said:
I have just installed a 38/38 weber on my 87 2f motor and have found it to be running rich as well. What jetting adjustment do you suggest?
Click to expand...

If you are above 3000 feet try 45 pilots and 145 mains. If my memory works at all, that should be close. Always change mains in pairs and the same with pilots on the synchronous carbs such as the 38/38.
 
I have had a few OEM Aisin carbs rebuilt....and the work GREAT!
I use Carbs R Us Located in Thomaston Ct. They do great work and have been in the carb business for over 25 yrs. Costs approx. $200-250 for the rebuild.
 
After having done a TBI upgrade on my 350, I am now of the opinion that this is THE way to go for the 2F as well, especially since wrecking yards are full of this stuff, it can be had CHEAP, it is easy to install (if I did it anybody can) and it is usually looked upon favorably in areas where emmissions testing is required not to mention the performance end of it. The new carb upgrade is EFI.
 
lehiguy said:
After having done a TBI upgrade on my 350, I am now of the opinion that this is THE way to go for the 2F as well, especially since wrecking yards are full of this stuff, it can be had CHEAP, it is easy to install (if I did it anybody can) and it is usually looked upon favorably in areas where emmissions testing is required not to mention the performance end of it. The new carb upgrade is EFI.
Click to expand...

Can you explain a bit more? I'm very interested in this. Is there a how-to somewhere for the 2f? I'm pretty sure Colorado will allow this since they're okay with a Weber being on there.

Also, for what anyone looking at this, I'm at 45 idles, 135 mains, and 190 airs at 5000 feet. Tomorrow I'll be testing emissions again - failed last time with 140 mains with CO going off the chart. Driving it today with the 135s it felt great. I have a set of 200 airs too but haven't put them in yet.
 
This is an old thread, however I want to throw my 2 cents into the fountain.

I bought a 88 fj62, 3F with a weber 38 w/ 29mm venturis (here in SA we didn't get the EFI on the 62's) that had been hacked in sometime during it's 430K kms. In fairness, they'd done a neat install but it was missing the choke assembly probably because here in SA it rarely gets cold enough to require it.

I got the car cheap because the carb needed attention, it was running overly rich to keep it from stalling and was in general set up wrong. I think the previous owner was fed up trying to get it right. I rebuilt the carb, and changed jets to match the high altitude here in Joburg, but nothing seemed to correct the erratic problems - wouldn't start warm (sometimes), would drain fuel out of nowhere (sometimes), would stumble on the highway (sometimes), would stumble on light acceleration (sometimes) ... the list goes on, but there was never a solid pattern that would allow me to actually diagnose anything. Also, it ate fuel like you could not believe.

In the end, I caved and bought an aftermarket aisan carb. It came horribly set from the factory, and I cocked up the install by feeding fuel down the vent hose instead of the threaded union style inlet :/. My cruiser no longer had the standard factory fuel line as it transpires. Anyway, so far, so much better. It's easier to tune, everything is there, and best of all it's a progressive carb. The weber was designed for "V" engines, and chucks fuel down the intake much faster than the standard carb, making low end tuning much trickier. At the end of the day you have to remember that the Aisan carb was designed for this car, and there is merit to sticking to it.

-Paddy
 
Revived once again. In regards to the Weber 38 being mainly bashed on both here and Pirate4x4.com, the arguments used in doing so could not be farther from the truth. As some have said, most that know how to tune their Weber's love them. You simply can not beat the rock solid reliability, absolute flawless performance on steep grades, and ease of access to work on and change jets. WHAT?! That's right. Out of the box, the float is not setup to be installed and driven, it has to be adjusted. Second, it HAS to be jetted correctly, and should be done using a Wideband AFR gauge. Lastly, 95% of the documentation on how to tune a Weber is extremely lacking in the information required to properly tune a Weber.

The Weber 38 has two circuits. A low speed circuit, and a high speed circuit. These refer to RPM operating ranges. There is also a transition phase between the two. Meaning if your Idle / Cruise (low speed circuit) was perfect up to around 2500 RPM, then your Main metering system would come into play and carry you to redline. The problem is, the Weber 38 was never intended to be installed on a 4.0 liter engine, and if one was going to use Weber carbs on a large engine, it would be several DCOE 40's etc. A Weber 38's largest engine size was to be a 2.3 liter engine.

So what happens when a Weber 38 is installed on a larger engine? There is much more air velocity coming through the carb, and that changes the time in which the barometric pressure (regulates fuel delivery) drops, and therefore, brings everything into play much sooner than on a smaller engine. For instance, you will be hitting your main metering system (high speed circuit) early in the RPM range of your F Engine Land Cruiser.

The second problem faced, is the Accelerator Pump / Pump Jet is insufficient for an engine of this size. On a smaller 1.8-2.3 liter engine, the .70mm pump jet would be fine, for instance, on the Toyota 22R. The Primary function of this system, is to dump fuel when you mash the throttle, as there is very little air velocity coming through the carb, and therefore it takes time for the main metering system to catch up. Unfortunately, the .70mm pump jet is already the biggest you can install, and it is installed by default on Weber 38's.

When I was learning all of this, I was tuning the Weber 38 on my 1985 FJ70 3F engine, using a AEM Wideband AFR gauge. I had the Idle Circuit / Low Speed Circuit dialed in exactly where I wanted it. Also, at WOT, I was sitting at 12.5:1, the perfect AFR for maximum and safe power at WOT. But still, there was this lean sag anytime I was not careful and gave her a little bit too much throttle off the bat, either when taking off from a stop light, or going to pass someone on the highway. I would watch my AFR's shoot straight from 13:1 - 17:1, then start working it's way back.

On every forum and site I could find, everyone said if you have a lean sag, up your mains. And so I did. I continued upping the mains until at WOT I was running 10:1 AFR, extremely rich, and guess what? The lean sag was still there. Clearly, upping the mains was NOT the answer.

Finally, found it I did. The way through the marshes. What no one has been told, and what almost everyone is mistaken on, is the "Air Corrector Jets." These jets are EXTREMELY important to achieve a "better than Aisan" setup. Here is why. The Air Corrector jets do more than just "trimm the fuel at high RPM." They are responsible for "Timing" the Main Circuit (Main Jets). I am at 8500 feet elevation, so I had been using a High Altitude Jet kit, and the Air Correctors included, were 190's, 200's, and 210's. So I purchased some 150's. 160's, and 170's. To verify what I was reading was correct, I installed the 150's hoping to see a drastic change. And I did. The AFR was extremely rich right off idle, and throughout the RPM range, but the lean sag was gone! So I changed my 145 mains down to 135's to see what would happen. It was still rich at cruise, and a little leaner than I'd like at WOT. Ok, so I split the difference. Changed the Air Correctors to 160's, and upped the mains to 140's, to bring the mains in a tad later, and give a bit more fuel when they did come in, and what do ya know! AFR's stay between 13.8:1 - 12.2:1 from off idle to 4000 RPM. The lean sag is non existent. The response and power is incredible, and it runs like a Fuel Injected engine. Cruise AFR is 14.1:1.

This setup took disassembling the Weber 11 times and changing jets while documenting changes in AFR etc. Only until the last 4 times did I fully understand the operation of the Air Corrector's.

8500 Feet Elevation - Toyota 3f 4.0 Liter Engine - 13.8:1 - 12.2:1 AFR Across RPM range.
Idle = 45
Main = 140
Air Corrector = 160

Taken from the Article "Weber Tuning Methodology"
• Main Air Corrector Jet - The main air corrector jet controls the volume of air to be mixed with fuel in the emulsion tube well. Changing to a larger size will admit more air. This produces a leaner mixture while changing to a smaller size will admit less air resulting in a richer mixture. The effect of main air corrector jet changes will be more noticeable at the upper end of this circuit's operation.

Another important function of this jet is to help control the start of high speed circuit operation. A smaller main air corrector jet will "start" the high speed circuit: at a lower RPM while a larger size will delay its entry.

You can see the work I've done to my Cruiser here at xtremecruisers.wixsite.com/website

Lastly, those of you running at 5000 feet with the same Idle jets and smaller main jets than I at 8500 feet, you are running LEAN! You are .2 liters bigger with the 2F, and 3500 feet lower! If I was at 5000 feet, I would run 50 Idles, 145 Mains, and a 160 Air Corrector. I warn you though, it may turn your FJ into a monster.
 
Good work and a very nice write up explaining what you did!:beer:
 
@FJ40Jim can you send me a pm with current turnaround time and cost for a desmog/carb refresh on a stock fj60 aisin carb?
 
The Weber 38 is by no means a “tiny” carburetor. A 2mm increase in diameter on one throttle bore does not make the Aisan “monstrous” in comparison. It is also highly unlikely that the engine could benefit from the added available CFM from the 40mm bore.

After calculating volumetric efficiency at a 85% (Mild Street Performance Engine), we find the demands of both are:

4.0 3F 4000 RPM = 240 CFM
4.2 2F 4000 RPM = 252 CFM

4.0 3F 4500 RPM = 270 CMF
4.2 2F 4500 RPM = 283 CFM

The Weber 38 has a flow rating of 380 CFM which far exceedes the required, and could not incur a bottleneck.

To quote FJ40Jim, “The weber 38/38 that is commonly sold as an upgrade has 38/38 throttles and 26/26 venturis.”

This statement is not accurate, the modern Weber 38 DGAS comes with 30mm Venturis. Which puts the Weber, directly in line with the 38mm bore and 31mm Venturi of the Aisan.

1965938


If that 1mm smaller Venturi is a problem, bigger isn’t always better, at least for low end grunt.

For most applications it is better to select a smaller main venturi diameter than what will provide maximum horsepower output. This is true for road cars as well as for race cars. It is therefore most important to be realistic with your intended application so an appropriate carburetor setup is achieved. A large venturi and throttle bore will provide high RPM power (assuming the engine components are up to the task: cams, compression, ignition, exhaust, inlet port diameter, intake valve diameter, etc.) but will do so at the expense of lower RPM tractability. Smaller venturis for a given application will shift the peak horsepower so it will be developed at a lower RPM with the benefit of more useable power throughout the RPM band which also says you will have more TOTAL available power than a high RPM engine of similar displacement would produce.

Another benefit from downsizing your venturi/throttle bore size is the smaller venturi (when compared to a larger venturi selection) will generate greater vacuum for a sharper signal to initiate fuel delivery from the main circuit. A higher vacuum results in sharper transition onto the main circuit and better atomization of the fuel resulting in decreased fuel consumption.

Throttle bore diameter recommendations for venturi diameter selections:

  • 30mm venturi: 37.5mm +/- 2mm
  • 32mm venturi: 40.0mm +/- 2mm
  • 34mm venturi: 42.5mm +/- 2mm
  • 36mm venturi: 45.0mm +/- 2mm
  • 38mm venturi: 47.5mm +/- 2mm
  • 40mm venturi: 50.0mm +/- 2mm
  • 42mm venturi: 52.5mm +/- 2mm
Looks like the Weber 38 Venturi size is exactly where it should be. 30mm for the 38mm Throttle Bore.

Carburetors can be set up and adapted to work with many different engine sizes, just because a carb manufacturer designed a carburetor specifically for a certain engine, does not mean there are not other suitable and agreeable alternatives. Aisan also designed the single barrel on the early FJ’s. What were they thinking?!

The Weber 38 powered 3F is anything but a dog, and has more low end grunt, power and responsiveness than it did with the Aisan. Not only this, but here in the mountains of Ecuador, I average 14 MPG, with hwy/cty split 50/50, and that is with the stock 4 speed manual trans.
 
I dont think my 2F has ever seen 4000 rpm when coupled to the transmission....happened once or twice when working through a sticking throttle problem.
 
I dont like to rev that high. All of that 135hp is not going to leap out and leave a scratch shifting from 1st gear to 2nd gear...

I've seen and driven both the Weber and Aisin equipped 60s and both run well if they have been properly tuned.

I 'm still have not made my mind which setup I will go with when I desmog.
 
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