cbmontgo
SILVER Star
Are 60 Series trucks sold at higher elevations jetted differently from the factory than those sold near sea level?
2F carb: high-altitude jets?
- Thread starter cbmontgo
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
I offer this as mere speculation, but I believe thta Toyota accomplished the mixture compensation via the HAC (high altitude compensation) valve.
cbmontgo
SILVER Star
- Thread starter
- #3
I had hoped that was the case, but I believe that the HAC only compensates up to about 4500' above sea level. I am running at 6,000-13,000' and I believe that my truck runs a bit rich, especially when up in the mountains.
The idle mixture screw is "blanked" off on my stock carb, so I want to take another route to lean it out. I hope that swapping jets may be an option, but I don't know if other jets are available from Toyota for this carb.
Can't you just do the drill-bit removal method to pop out the "blank" on top of the mixture screw and go from there?
That's what the FSM suggests for idle mixture adjustments. The idle mix screw came capped to meet US emissions requirements, right?
That's what the FSM suggests for idle mixture adjustments. The idle mix screw came capped to meet US emissions requirements, right?
Drilling the cap off the idle mixture screw will allow you to adjust only the idle mixture. While that is not a bad thing, it will have no effect on anything other than the idle mixture. They do have replaceable jets, you might try pulling them and looking for something smaller.
I installed a smaller main jet. I got it from Mark's Offroad. There is no point to adjust the idle mixture unless it is idling rich. Any naturally aspirating engine is going to run worse at a higher altitude. You have about 40% less pressure at 12K. You could install a smaller jet but you want to make sure you are not running too lean. It is better to run slightly rich.
This is what is nice about a turbo. The decrease in power is not as fast with a turbo as the altitude increases.
This is what is nice about a turbo. The decrease in power is not as fast with a turbo as the altitude increases.
That is the procedure. You drill out the blank and then you can adjust the idle mixture. That would help some but only when you are idling. Search for the lean drop method and use a vacuum gauge.
cbmontgo
SILVER Star
- Thread starter
- #10
I appreciate the help. Just FYI, this issue first came up last summer when I moved to Colorado from Dallas. I was wheeling at about 11,000' feet and my engine died; it clearly was too rich where the air is thin up there. I had to roll the truck down the hill about 200' in elevation to get it to start back up. I then drove another route that was less steep up the mountain, and it died again at the exact same altitude. Other stock 2Fs here in Colorado can cross the Divide with no problem. I can't figure out if this is a jet issue or an idle mixture issue.
- Joined
- Jun 28, 2002
- Threads
- 165
- Messages
- 2,105
- Location
- Colorado Springs, CO
- Website
- www.mntoyx4.com
You should not need to re-jet your carb. If the HAC system is complete and operational it should do all the work.
Has the carb ever been rebuilt? You don't have any vacuum leaks and your vacuum lines are in good shape?
60wag
SILVER Star
I messed around with some other jets but went back to stock as they performed the best. The HAC circuit is an on/off thing that is supposed to change state around 3500 (4500?) ft. No further changes take place at higher elevations. My 2F'd 60 did ok at 12,000 ft. It took a bit longer to start but ran well enough in the thin air. I would imagine that good compression would have an even larger impact at high altitude - I had a rebuilt engine with a 0.050" head shave.
cbmontgo
SILVER Star
- Thread starter
- #14
I rebuilt the carb with OEM parts about 2 years ago. I also replaced all of the vacuum lines at that time. I thought at first that a new HAC valve would do the trick, but was later told that it doesn't have any effect above about 4,500'.
The engine is very strong with great compression and has always run perfectly (and still does, but just not above the treeline).
I removed my stock carb shortly, VERY shortly after I purchased the rig. Puke and die was the typical MO when in the mountains on something steep. It probably could have been rebuilt, but I choose to replace it with a Weber which I ran for many, many years and it worked extremely well once jetted properly for my altitude. I'm pretty good at carb tuning on the simple stuff, but I'm just not a fan of Asian carbs or any carb with emissions crud on it; makes it too complicated for a simpleton like me. One thing you might check is the actuator for the secondary on your carb. Sounds like it isn't working. Find Jim C. and PM him, he'll know what to do.
cbmontgo
SILVER Star
- Thread starter
- #16
I emailed Jim C last week from my phone; either the email didn't go through or he hasn't had a chance to respond yet. I hope he'll see this thread and give us his 2 cents.
I have heard good things about the Weber, but I am an OEM guy and want to keep it stock whenever possible. Thanks for the help.
Anymore info on this? I'm currently having the same issues now that I've moved to CO.
1911
chupacabra
I've had my de-smogged '80 40 at high altitude and was surprised how well it did. A little less power going up a steep hill but that's about it.
I have recently moved to AZ and live at an altitude of 9300 ' . My de smogged 60 ( webber) runs well here but lacks the power it had at sea level. I had to adjust the high idle ( auto choke ) and the choke setting so the rig could warm up unattended with out stalling . The issue is Most of my driving will take me to lower elevations. So I am still on the fence about re jetting . As some one earlier said I would rather be running a little rich than too lean.( Fouled spark plugs are cheap compared to burned valves)
