Carb Tuning for Ouray Trip

[Ralph]

From what I can tell touring the web for travel information, I'll be traveling in elevations ranging from less than 500' to over 11,000'.

My Jeep has a Carter AFB-9635S (identical to an Edelbrock 1400, except that the Carter comes with spring-loaded needle & seat assemblies). The manual states as a rule of thumb, beyond altitude of 4,000', to decrease primary jet size 0.001" per 1,000' of elevation.

Should I bring a set of primary jets and stop to recalibrate my carb every so often?

[joe]

Ralph, I haven't had any experience with an AMC motors at extreme elevations(8k+) but when I used to do mineral exploration(CO,MT etc) and running sbc motors in company 4x4's a general rule of thumb was advance the timing 2* per/1000ft for anything over 6000 ft. It's still gonna run rich but the "ping" prob is canceled out do to running rich. It's not a 100% fix for running smaller jets but should get you by. We'd be on a job for two weeks at a time and never had a prob with stalling etc but be sure to set the timing back when down below 6000 ft.
Jets and gaskets are cheap though and it wouldn't hurt to bring along a couple options along with a spare set of plugs you can clean and swap out.
Again I don't know how well this'll work in an AMC motor?

[Kenall]

hey joe
what about an 1973 SBC with a holley 500 2bbl, basically the front half of a 750?

im using 67 jets down from the OE 73s and i have the timing set down from the OE spec of 12 to 10. runs great at SL, but at 6kft, im down on vac from 21 to 16. m afraid to find out what ill be at 11k :(

[Damage, Inc.]

We're at 6K feet here in COS...for the most part, I can run up to 10K without any major hiccups; after that, EVERYTHING suffers. Above 13K you're pulling off the air cleaner and just using a spray bottle of gas into your intake!!!

As a guideline, you get less oxygen the higher up you go; your jets should adjust accordingly...or buy a winch and coast downhill..

[Don S]

Ralph.. At 11,015 feet you turn off the pavement of Hwy 550 and THEN you start climbing a mountain. Imogene Pass is 13,114 feet and there are trails above that. I use Two Cycle Outboard Oil such as Pennzoil to help keep the spark plugs clean a special additive helps clean out and prevent carbon deposits.the link below may be of some help.. good luck.. ;) ds..

http://groups.msn.com/ATexasOklahomaJeepClub/ouraycotopic.msnw?action=get_message&mview=0&ID_Message=49&DDir=-1
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[joe]

Originally posted by Kenall:
hey joe
what about an 1973 SBC with a holley 500 2bbl, basically the front half of a 750? Ken, I don't enough about the Holly but if it has an altitude compensator(and assuming nobody has taken the alt curcuit apart previously...bad thing to do) as the stock MC/Holly on 70's+ FSJ's do you'll prolly be fine. Otherwise I'd plan on bumping up the timing of the sbc motor.
It's a different ballgame with different rules for most carbs at 10,000 feet than it is at sea level. smile.gif

[Jeepzilla]

All this caring for the machinery! What about the biological units? Oxygen is mandatory for pilots above 12,000 ft. Do you guys carry O2 to sniff while tuning your carbs?? :D :D

Ralph--are you gonna get those new rims dirty? How dare you! :eek:

[Ralph]

Joe: Thanks for the advice. I'll be taking a set of jets, a vacuum guage, and a timing light with me. So I guess a stop in Denver will be the right place to start making changes.

Also curious to know to what extent the altitude will affect tire pressure.

'Zilla: Yep, the rims are going to Ouray. I got them back from RediStrip Thursday. I wanted to get them painted today, or at least get some VariPrime (self-etching primer) on them, but I just can't find the time. They're nice clean metal now, so I hope they don't grow any rust freckles for at least another week. I'm going to paint them the same Olympic White as the bottom half of my J10, and I got a set of brand-stinkin' new center caps coming from a source in Australia. I'll be putting these tires on them:

eBay Motors # 1843502491 (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1843502491&r=0&t=0&showTutorial=0&ed=0&indexURL=0&rd=1)