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View Full Version : WTB high altitude carb jets


cbmontgo
10-19-2010, 10:57 AM
I am rebuilding my carb this week and was told that I am running sea level jets in my 1976 FJ40 (currently running 1.44mm & 2.30mm, pri and sec mains, respectively).

Anyone have a set of high altitude jets that they are willing to sell?

cbmontgo
10-19-2010, 11:11 AM
...and maybe the power valve too? I don't know what else might need to be replaced for this elevation; I'll take any advice I can get.

RicardoJM
10-19-2010, 11:18 AM
Do you know what size you are needing? I've got some spare jets that I could look through at home. Typically the high altitude jets are smaller.

The early 70s (late 69 to -74, IIRC) carbs came with the high altitude jets stored in the fuel bowl plugs. It is my understanding that Toyota stopped this at the time they added the high altitude compensation system. I am thinking you need these jets for your 1976?

Finding jets is a bit of a challenge in that Toyota did not have the size I was looking for.

cbmontgo
10-19-2010, 11:26 AM
Do you know what size you are needing? I've got some spare jets that I could look through at home. Typically the high altitude jets are smaller.

The early 70s (late 69 to -74, IIRC) carbs came with the high altitude jets stored in the fuel bowl plugs. It is my understanding that Toyota stopped this at the time they added the high altitude compensation system. I am thinking you need these jets for your 1976?

Finding jets is a bit of a challenge in that Toyota did not have the size I was looking for.

Ricardo, thanks for the post. That is correct about spares; the '75 and newer did not come with spares unfortunately (right about when the 2F came along). The '76 is also prior to the HAC system, so leaning the mixture relies solely on the carb itself.

Right now, I am running 1.44mm & 2.30mm primary and secondary mains, so anything smaller than that would be good. I think I probably need 1.14mm and 1.80mm from what I've read, but I really don't know for sure.

RicardoJM
10-19-2010, 11:41 AM
I'll look to see if I have something smaller than 1.44.

[disclaimer] Your generation (post 74) of Aisan is not one that I am as familiar with, but I have learned/experienced some things with the early carbs I have rebuilt. It may or may not apply. [disclaimer\]

Regarding jet sizes, small changes matter - recently I started with 1.08 which is the "high altitude" main jet size in the FSM. I then went through 1.12 and finally ended up at 1.14. All three of these jets worked but there was a very slight stumble when making the transition from idle with the two smaller ones. Bit of a long winded way of saying, a jump from 1.44 down to 1.1x might be too big a drop.

Air Randy
10-19-2010, 11:43 AM
Do you know what size you are needing? I've got some spare jets that I could look through at home. Typically the high altitude jets are smaller.

The early 70s (late 69 to -74, IIRC) carbs came with the high altitude jets stored in the fuel bowl plugs. It is my understanding that Toyota stopped this at the time they added the high altitude compensation system. I am thinking you need these jets for your 1976?

Finding jets is a bit of a challenge in that Toyota did not have the size I was looking for.

What size did you put in yours? It seems to be running right for this altitude, if you give him the same size he should be OK.

RicardoJM
10-19-2010, 11:54 AM
What size did you put in yours? It seems to be running right for this altitude, if you give him the same size he should be OK.

1.14 is what I ended up with in mine. I know I don't have another 1.14 as the one I have came from Martin. The jump of 3/10s just seems like it is huge. I suppose there is no harm to giving it a try. If it makes it worse, we can always go back to what is in there now. :D

cbmontgo
10-19-2010, 12:41 PM
I appreciate the help, Ricardo. Let me know what ya find.

RicardoJM
10-19-2010, 06:41 PM
I appreciate the help, Ricardo. Let me know what ya find.

Here is an inventory of what I have in the spares bag. Let me know if you'd like to give any of them a go.

Primary/Secondary Jets
103
108
112
118
141
147
159
200

Power Valve Jets
40
60
70
90


"Slow Jets"
50
65
80
90

cbmontgo
10-19-2010, 07:33 PM
Awesome; thank you very much Ricardo. Is there any way to know which power valve I have right now? Are they stamped like the jets?

Let me do a little more research on this topic and I will definitely be in touch.

I hear so many different opinions on ih8mud...some say just to replace the primary, some say replace both, some say replace the primary and power valve, some say keep the existing stuff if it runs right...I just don't know what the hell to do.

It does run great here in Castle Rock at 6,400', but I want it to be slightly lean here and really run great up in the mountains. I hope that I can get this figured out...

RicardoJM
10-20-2010, 07:03 AM
Is there any way to know which power valve I have right now? Are they stamped like the jets?

The power valve jet is on the bottom of the power valve. you need to remove the air horn to access the power valve. The power valve is removed with a 1/4" drive 9mm deep socket.

Yes, all the jets I have seen in Aisan carburetors are stamped. A magnifying glass is often needed. The one I have has two smaller circles that really up the magnification and I most often go right to the strongest magnification.

Air Randy
10-20-2010, 09:03 AM
It does run great here in Castle Rock at 6,400', but I want it to be slightly lean here and really run great up in the mountains. I hope that I can get this figured out...

Where do you plan on driving the rig the majority of the time? If that will be in Castle Rock, then I would caution against setting it up to run lean here. Running lean will increase the combustion temps and is hard on your valves besides reducing your power.

Set it up to run the proper mixture here, then when you go up to higher elevations it will run only slightly richer. That won't hurt anything as long as it isn't so rich that it's pumping out black smoke and fouling the spark plugs. Most people have issues in the mountains because they're already running too rich at Front Range elevations.

If the vehicle is still driveable I would take it to the place Ricardo uses and have them check it for emissions. They can tell you if you are running rich on idle or on power. If you are, they can then give you suggestions on how many jet sizes to reduce to get to the right mixture. Then open your carb up to see what sizes you have and figure out what sizes you need to go to based on the shops recommendation.

cbmontgo
10-20-2010, 09:17 AM
Where do you plan on driving the rig the majority of the time? If that will be in Castle Rock, then I would caution against setting it up to run lean here. Running lean will increase the combustion temps and is hard on your valves besides reducing your power.

Set it up to run the proper mixture here, then when you go up to higher elevations it will run only slightly richer. That won't hurt anything as long as it isn't so rich that it's pumping out black smoke and fouling the spark plugs. Most people have issues in the mountains because they're already running too rich at Front Range elevations.

If the vehicle is still driveable I would take it to the place Ricardo uses and have them check it for emissions. They can tell you if you are running rich on idle or on power. If you are, they can then give you suggestions on how many jet sizes to reduce to get to the right mixture. Then open your carb up to see what sizes you have and figure out what sizes you need to go to based on the shops recommendation.

Randy,

One interesting thing about emissions...since 1976 is no longer excluded from emissions testing, I had it done this past spring when I bought the FJ40. The test showed that the air/fuel mixture was appropriate, but I don't know how accurate those things are? It showed that it was right on target. Should I trust that?

I will drive it here in the Front Range 95% of the time. My fear is to be driving up I-70 and the engine die at the Eisenhower Tunnel because of a super-rich mixture.

The advice I received on 'Mud about this was to leave well enough alone.

By the way, what is the elevation up where the Spooky Night Run will be this year?

SteveH
10-20-2010, 09:19 AM
A buddy of mine pointed out that many Toyota carburetors share parts, so if you're at the pick-and-pull, and you see a carb'd pickup or Corolla, you could liberate the jets from the carb, to add to your collection. You might stumble across the ones you need and/or ones no longer available in the open market.

subzali
10-20-2010, 09:20 AM
...
If the vehicle is still driveable I would take it to the place Ricardo uses and have them check it for emissions. They can tell you if you are running rich on idle or on power. If you are, they can then give you suggestions on how many jet sizes to reduce to get to the right mixture....

Is this an AirCare place? Or somewhere else? I would like to know about this too...my FJ40 runs great all the time, no matter if it's 5000 feet in Utah or 13000 feet on Argentine Pass or Mosquito Pass. I guess I probably shouldn't change anything, but still I'm curious about where it sits air/fuel ratio-wise. I need to check my jets too and see what they are.

RicardoJM
10-20-2010, 09:46 AM
Is this an AirCare place? Or somewhere else?

The shop is:
Colorado Car Clinic
5311 S Broadway, Littleton, CO.
Phone: 303-730-0055

These guys have the same equipment that is used by the "Tail Pipe Only" emissions stations and were able to tune my rig to get it through emissions. I'm sure they are not the only shop that has the equipment needed to analyze the air fuel mixture.

Air Randy
10-20-2010, 01:52 PM
I will drive it here in the Front Range 95% of the time. My fear is to be driving up I-70 and the engine die at the Eisenhower Tunnel because of a super-rich mixture.

The advice I received on 'Mud about this was to leave well enough alone.

By the way, what is the elevation up where the Spooky Night Run will be this year?

If you really want to know I would spend the money and take it to Car Care to get their take on whether it is running rich or is OK as-is. I wouldn't totally trust the emissions test results for this purpose.

If Car Care says it is OK and it runs good here, you should not have any issues when at higher elevations. I would tend to agree with the "leave it alone and run it as-is" approach.

I have an oem carb on my 74 that does not have a HAC. I had JimC rebuild it and tune it and it runs great at all elevations. Unless you have something else wrong with your carb causing it to run too rich you should be OK.