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-   -   Carb jetting for altitude (http://www.risingsun4x4club.org/forum2/showthread.php?t=12851)

cbmontgo 04-20-2010 09:34 AM

Carb jetting for altitude
 
Where do you guys source smaller orifice sizes for stock Aisin carb jets? I've got a '76 FJ40 that needs to be jetted for this elevation. Unfortunately, the spare high altitude jets seem to have gone away in '74.

Do I just need to replace the primary jets or the others as well? Any orifice size recommendations for our elevation in the Denver area?

Just got this rig up here and it runs REALLY rich. I'm going to rebuild the carb while I'm in there.

RicardoJM 04-20-2010 11:32 AM

I tried Import Carb Warehouse and they did not stock them. Toyota no longer has them. I pulled a couple from a Corolla, but they were not even close to the size I was needing. I was fortunate enough to get some jet advice from JimC on MUD - but could not find a 60 for one of slow jets. I went with a 50 in both.

My rebuild has been running in my 40 for over 4 months and is doing just fine. Take your time, plenty of pictures and notes and enjoy the experience. If you have any questions, I'm happy to share what I can.

cbmontgo 04-20-2010 01:13 PM

Quote:

Originally Posted by RicardoJM (Post 147042)
I tried Import Carb Warehouse and they did not stock them. Toyota no longer has them. I pulled a couple from a Corolla, but they were not even close to the size I was needing. I was fortunate enough to get some jet advice from JimC on MUD - but could not find a 60 for one of slow jets. I went with a 50 in both.

My rebuild has been running in my 40 for over 4 months and is doing just fine. Take your time, plenty of pictures and notes and enjoy the experience. If you have any questions, I'm happy to share what I can.

Thanks, Ricardo. What a cool writeup! I am about to take some time and read through it prior to my upcoming carb rebuild.

I rebuilt my FJ60 Aisin carb in 2007, but I don't know why I am nervous about this FJ40 carb. I guess the jetting thing has me concerned, especially since Toyota no longer has them and I am having a hard time running these parts down.

MDH33 04-20-2010 01:15 PM

I have some spare jets. Let me know what sizes you decide to run and I'll see what I have.

cbmontgo 04-20-2010 01:21 PM

Quote:

Originally Posted by MDH33 (Post 147062)
I have some spare jets. Let me know what sizes you decide to run and I'll see what I have.

Thanks Martin! Let me get this thing torn down and I'll PM you.

I've read that some people up here use 1.08 mm primary jets (maybe see if you have a size close to that?), but do I also need to change out the power valve and the slow valve?

MDH33 04-20-2010 01:35 PM

Quote:

Originally Posted by cbmontgo (Post 147064)
Thanks Martin! Let me get this thing torn down and I'll PM you.

I've read that some people up here use 1.08 mm primary jets (maybe see if you have a size close to that?), but do I also need to change out the power valve and the slow valve?


What jets do you currently have?

The recommended starting place for jets at higher elevation (according to Jim C and tested by myself and Ricardo) are:

112 or 114 Primary
180 Secondary
50/60 or 50/50 slow
and 60 Power Valve

RicardoJM 04-20-2010 01:54 PM

Quote:

Originally Posted by MDH33 (Post 147062)
I have some spare jets. Let me know what sizes you decide to run and I'll see what I have.

Quote:

Originally Posted by cbmontgo (Post 147064)
I've read that some people up here use 1.08 mm primary jets (maybe see if you have a size close to that?), but do I also need to change out the power valve and the slow valve?

Once you decide what you want to run, I'll check what I have that you need. It all begins with first learning what you have in there.

I am assuming this is your new FJ40 from AZ. Before diving into the carb rebuild have you gone through some tune up basics and checked for vacuum leaks? New plugs, dizzy cap, rotor, points (if you don't have electronic ignition), valve adjustment and timing check will give you a good baseline. Fresh 15w40 and filter don't hurt. If there are any vacuum leaks, you will not ever get the carb working well until they are gone. :thumb:

cbmontgo 04-20-2010 01:55 PM

Quote:

Originally Posted by MDH33 (Post 147065)
What jets do you currently have?

The recommended starting place for jets at higher elevation (according to Jim C and tested by myself and Ricardo) are:

112 or 114 Primary
180 Secondary
50/60 or 50/50 slow
and 60 Power Valve

I need to take it apart and see which ones I have. It ran perfectly in Arizona when I dropped it off to be shipped here, but then had some starting issues in Phoenix and runs like hell here. I'm not sure what the issue is, but I am guessing that leaning it correctly is a start.

It only drives/idles if you throttle it up at the carb. If you give it gas, it bogs down and dies. Spits nasty black smoke and smells strongly like gas.

cbmontgo 04-20-2010 02:00 PM

Quote:

Originally Posted by RicardoJM (Post 147067)
Once you decide what you want to run, I'll check what I have that you need. It all begins with first learning what you have in there.

I am assuming this is your new FJ40 from AZ. Before diving into the carb rebuild have you gone through some tune up basics and checked for vacuum leaks? New plugs, dizzy cap, rotor, points (if you don't have electronic ignition), valve adjustment and timing check will give you a good baseline. Fresh 15w40 and filter don't hurt. If there are any vacuum leaks, you will not ever get the carb working well until they are gone. :thumb:

I am trying to order the cap, rotor, wires, etc. from Go Toyota on Arapahoe, but they are taking forever and don't seem to be very interested in my business. I really don't want to buy aftermarket if I can avoid it. I did change the oil and filter yesterday. Have not checked timing or adjusted valves yet.

I have visually inspected for vacuum leaks, but it's really strange that it had a hard time starting in Phoenix to be loaded onto the truck after it ran perfectly for 100 miles when I picked it up in Congress, AZ. Could this be an intake manifold crack causing the vaccum leak? I figure that it needed a carb rebuild anyway and I can at least isolate that as an issue. My FJ60 acted similarly when it needed a rebuild.

SteveH 04-20-2010 02:39 PM

Given how all my federal-spec (low elevation) trucks have run at 7000' (my house), I don't think jetting is the first place I'd look. Do a 100% by the book tuneup (timing, idle mix, etc.) and check vacuum advance function, and look for vacuum leaks, etc. and see if that doesn't help greatly. My truck does run rich at very high elevations -12K, but that would be normal for any carburetted vehicle. Rejetting is a pain, IMO...start with easier stuff first.


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