Idle speed for 2F w/ Weber

Spino

Spino

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Boulder, CO
Hi folks. I’ve been gradually getting my desmogged FJ60’s Weber carb jetted after living with a vacuum leak for too long. Here’s the question, briefly:

What is the preferred idle speed for a 2F engine? There seem to be a range of answers out there. I’m not sure if the general Weber tuning spec applies (700-900rpm) for my engine.

More background, if you’re still reading: I bought this truck about a year ago. PO had desmogged it and put in the Weber (I know, I know, lots of hate for Weber carbs on Mud. Don’t blame me!) I finally replaced the stupid 2-piece manifold adapter with a one-piece unit from JT Outfitters. The telltale vacuum leak whistle went away. But now the jetting was off. Got a jet kit and started tinkering. It is now to the point where it starts pretty easy, idles fine, cruises real nice just off idle, and it isn’t so bad at WOT. Minimal stumble when I get into the main circuit, once things are warm. BUT … idle speed is 500rpm, which seems low. I live at 7000 feet, and I really can’t go much leaner on the idle jets. Just not sure if I’ve got it as good as it can be or if I should try something else to bring up the idle speed.

Thanks!
 
OSS

OSS

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The factory spec for a stock 2F engine is 650 RPM — but I always felt that was a bit too low — so I set mine higher.
You can set the idle speed wherever you want. The engine is happier idling faster, it just wastes fuel.

Toyota has to walk a fine balancing act recommending an idle speed. Fuel economy is always part of their equation, so is idling emissions.

When the 2F is at a perfect operating temperature and perfectly tuned up and the engine is in tip too shape, 650 RPM works ok, but I found the engine was happier in real world conditions went set to at least 750 RPM.
 
Seth S

Seth S

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750 to 800 the engines definitely seem happier. You get up into the 1000 rpm range and the truck starts to drive itself. The factory 650 definitely seems low and can be a real touchy target to hit unless you have refreshed and properly adjusted everything to oem spec.
 
John Staton

John Staton

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So I got my 83 desmogged, added headers and swapped to a weber 38 a couple years ago. Real happy with it. It did take a bit of tuning. At first I had it set way too high and it would diesel real bad after shutting it off. It would also stumble between lower gears. The answer was to open the jets up and set the idle lower. I think mine is happy around 650-700. Always starts and idles great. I have adjusted it a bit higher based on my AC running, but I think its still around 700. It will rev higher (around 1000) when I first start it and I give it a small punch and it ildes down.
 
Spino

Spino

Joined
Jul 18, 2020
Messages
52
Location
Boulder, CO
So I got my 83 desmogged, added headers and swapped to a weber 38 a couple years ago. Real happy with it. It did take a bit of tuning. At first I had it set way too high and it would diesel real bad after shutting it off. It would also stumble between lower gears. The answer was to open the jets up and set the idle lower. I think mine is happy around 650-700. Always starts and idles great. I have adjusted it a bit higher based on my AC running, but I think its still around 700. It will rev higher (around 1000) when I first start it and I give it a small punch and it ildes down.
Cool, thanks. Mine is a 32/36 but I’m guessing the fundamentals are similar? I have gradually leaned out the idle jets (I’m at 7000 feet), but it seems to hit a point where idle speed refuses to go much higher than 600 unless I keep turning the speed screw in. Based on my reading and general understanding, this is not right because eventually the carb bypasses the proper idle circuit via the butterflies. My air screw is to spec, 2 turns out, but at this rate, the speed screw needs to be 2 turns in or so to get it close to 700rpm. Maybe something else is going on here?? Thanks!
 
John Staton

John Staton

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Cool, thanks. Mine is a 32/36 but I’m guessing the fundamentals are similar? I have gradually leaned out the idle jets (I’m at 7000 feet), but it seems to hit a point where idle speed refuses to go much higher than 600 unless I keep turning the speed screw in. Based on my reading and general understanding, this is not right because eventually the carb bypasses the proper idle circuit via the butterflies. My air screw is to spec, 2 turns out, but at this rate, the speed screw needs to be 2 turns in or so to get it close to 700rpm. Maybe something else is going on here?? Thanks!
I read a lot of posts on here about the Weber and it seems like the consensus was that the 32 wasn't a good fit and I needed to make sure to get the 38, but its been a while. Lots of threads on it. And dont be too concerned about the carb purists on here....whatever works that you can keep tuned is your best solution. I have a nice truck that and have tried to keep looking classic/OEM but worrying about keeping pure under the hood came second to keeping it simple and getting rid of all the vacuum lines, etc....so I can enjoy it.
 

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