Adjusting Weber for large elevation changes?

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MrWrench
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Adjusting Weber for large elevation changes?

Post by MrWrench »

Hey guys, I am taking Spud with 3 dudes and a load of spare parts and camping gear out to Colorado and driving through the rocky mountains this summer. The trip will be about 3,500 or so miles.
My car is currently tuned pretty well for where I live. Which is 800 feet above elevation. Looking into my route and the town's I'll be staying in have a elevation of 6,000+ feet with possibilities of getting higher than that.

So I am wondering if you guys think about tuning adjustments for the elevation changes.

1. Jets
Do you guys think it'll be okay with the factory jets?
A jet kit is relatively inexpensive, but I don't know if it'll be necessary to do.

2 . Air fuel ratio.
I was thinking about getting a wide band oxygen sensor and gauge. They're pricey, but it would be nice to know how the car is responding and adjust it accordingly.
And if I decide to run a wide band, what is a good reading I should maintain between and a maximum/minimum air fuel ratio I should run before I have pinging and detonating issues?

Thanks in advance everyone!
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
The Professor
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Re: Adjusting Weber for large elevation changes?

Post by The Professor »

I'd suggest keeping the AFR as close to 14.7 as you can, leaning toward 13:1 or "rich" for safety. Anything above 14.7:1 is considered "lean" and could cause detonation.
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teranfirbt
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Re: Adjusting Weber for large elevation changes?

Post by teranfirbt »

Back when I had my Weber I had it tuned well for near sea level and then took a trip to Texas. It did just fine without any adjustments, ran pretty rich in the high elevations at high loads, but otherwise did well. If it's only a road trip, I wouldn't worry much about a trip over the rockies, it'll be fine.
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wild scallion
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Re: Adjusting Weber for large elevation changes?

Post by wild scallion »

It may or not be applicable to your route, but for elk hunting at 10500ft I had two seasons of trouble getting that high. The third year we added a fuel line onto the unused side of my weber's "t" just before the carb, and had a hand pump and pony tank (our "Icarus tank") to manually add fuel into the carb. Worked great, really. Did it make sense? unsure. But if you were going that high for any length of time, a fifty dollar prepared setup might be useful for that cause.
Between 9500 and 1500 feet throughout travels I didn't notice any glaring performance issues. (Maybe due to the steepness of the slope, too..)
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MrWrench
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Re: Adjusting Weber for large elevation changes?

Post by MrWrench »

wild scallion wrote: Wed Jan 29, 2020 12:21 am we added a fuel line onto the unused side of my weber's "t" just before the carb, and had a hand pump and pony tank (our "Icarus tank") to manually add fuel into the carb.
You've intrigued me with this information.
Recently I installed an electronic fuel pump to try and help.with my horrible no start issues with my Weber carb. I believe I am somehow losing fuel from the bowls after a while.
Now with the electronic pump, I can just let the car prime itself for 15-20 seconds and it starts effortlessly.

My questions are this, did you have to adjust your fuel pressure for the second line? And did you just run a line directly into the open secondary port in front of the Weber? Or did you just T off your line from the pump/pressure reg to the other spot? I am genuinely curious and would love a photo if at all possible.

Thank you so much everyone for your responses!
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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wild scallion
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Re: Adjusting Weber for large elevation changes?

Post by wild scallion »

Sorry, haven't been around for a spell.
In reverse order to your inquiry, the new line ran from the pony tank behind the drivers seat up through the cabin, one way squeeze-pump next to the hand-brake, then hosed through the firewall forward of the passenger's seat, straight up to the port-side of the "t," forward of the weber.
I never addressed (or even detected) pressure problems, and maybe it was super dumb of me not to worry about pressurizing fuel into the cabin, but it never seemed to, and I got away scot-free. I have since moved to sea level and the icarus tank is no more.
Now I feel like I need a disclaimer to explicitly say: I do not recommend or endorse any action that may expose you or someone else to pressurized fuel. So, there. But I did. And it was fun.
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Re: Adjusting Weber for large elevation changes?

Post by dlb »

I see a vacuum leak in your pic:

20211104_124948.jpg
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Petros
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Re: Adjusting Weber for large elevation changes?

Post by Petros »

no automobile on the road, or on any race track for that matter, allows fuel lines to pass through the passenger compartment. There are both Federal DOT requirements (and in most of the world too), and most racing organization specifically ban it in their rules. seems like a really bad idea, if a leak should develop, you would be lucky to survive it uninjured.

when I first started working on cars when I was in high school, aircooled VWs were very popular. when we would go to the wrecking yard to find parts for our old cars, I recall counting 9 cars that ended up there because of fires, 8 of them were aircooled VWs. that engine compartment, sealed off for the cooling system, trapped leaking fuel and eventually caught on fire. outside an enclosed compartment, any leaks would drip on to the ground and not be as much a hazard to the occupants.
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