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tuning for altitude |
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jhg 
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Joined: 07 Nov. 2016 Location: colorado Status: Offline Points: 917 |
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 Topic: tuning for altitudePosted: 25 Dec. 2017 at 8:54pm |
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My '48 has a re-built Go-Devil with a Solex on it. I live at 5000' and wheel north of that up to around 12,000' sometimes. What should I be aiming for and what adjustments do I need to make for running at these altitudes? Timing advance? LO or High jets? Do I need to order a special jet if such a thing exists for these carbs? Thanks, Joshua
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1948 cj2a. Rebuilt L-head, steering, T90, WO 636, steering, brake lines. So far.
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lowenuf
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Posted: 25 Dec. 2017 at 10:43pm |
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I live in Ohio, at 800' above sea level. This past September, I spent a week in the Nathrop area, wheeling my restored 1945 CJ2A with an L-134 Go Devil and WO carb, up to and including Mt. Princeton, Antero, and Aspen Ridge. Not once did I have to adjust anything for altitude. My unit worked flawlessly all week. I personally am not a Solex fan, but I do know that you must use a fuel pressure regulator for proper operation. Having said that, I do not know if altitude would affect fuel pressure to your carb....
My avatar pic is me behind the wheel of CJ-2 #09, with it's owner, Fred Coldwell at Marshall's Pass, and again, no adjustments were made...... Edited by lowenuf - 25 Dec. 2017 at 10:47pm |
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45 #10012
45 #10033 ACM #47 45 #10163 ACM #188 57 CJ5 Dauntless V6, T-18 4-speed, D-44 rear/D-30 front, D-20 twin stick |
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Lee MN
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Joined: 13 Aug. 2008 Location: Harris, MN Status: Offline Points: 4945 |
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Posted: 26 Dec. 2017 at 12:01am |
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Like Lowenuf, I am not a Solex fan and have no idea what is required for altitude. My 2A has been to Colorado several times, Pikes Peak, FCT, Black Bear Pass, Imogene Pass, many others in the Ouray area, and the Lead King Basin, I've changed nothing from home to any of those places with NO issues, stock WO Carter....... One thing you want to do is make sure your fuel system is in top condition, that being your tank/fuel line/fuel pump are in top condition, CLEAN and leak free with no Worm style clamps on filters and hoses.
Lee 
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LEE
44 GPW-The Perfected Willys 49 2A “If you wait, you only get older” 67 M715 American Made Rolling History |
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Steelyard Blues
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Joined: 09 Oct. 2017 Location: Reno, NV Status: Offline Points: 1496 |
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Posted: 26 Dec. 2017 at 2:58am |
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You could give the economy kit a try. It would lean it out a bit. Also, I believe a similar carb model is used on old VWs. My friend just put two on a '72. A local bug shop might have some ideas on tuning for elevation.
  Micah |
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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oldtime
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Posted: 26 Dec. 2017 at 4:01pm |
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It's been my experience with stock Go-Devil having the Carter WO; that fuel metering "WAS" effected. Specifically when Jeep was running up a Colorado high mountain pass while attempting interstate speeds above 50 MPH.
I don't recall any note-able problems when it was operating at high altitude and much slower speeds. My experience was over 40 years ago, yet should remain valid It's my opinion that when Carter WO is at wide open throttle (WOT); precise main jet metering becomes a real concern. If operating at high altitude and WOT the engine will burn overly rich and that quickly causes carbon build up on the plugs. To remedy, the main metering jet needs to be down sized. That effectively increases the air percentage. Whether or not you re-jet; the power output will be decreased. The big difference are the effects from running an over rich fuel mixture. Might simply try increasing the vac advance a little and or install next hotter set of plugs. The hotter plugs like Champion J6-C should help them to burn cleaner
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Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963) Zero aftermarket parts |
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TERRY
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Posted: 26 Dec. 2017 at 4:37pm |
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I advance timing about 5 more deg. If it kicks back on starting you've gone too far. Rule of thumb is 1 deg for each 1000' in elevation, but i never bother with more than the initial 5-6 deg base addition.
I live at 6000'. |
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BOULDER 48 2A
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jhg
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Posted: 26 Dec. 2017 at 8:32pm |
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This is all helpful. Thanks I have a lot of little things to do to get ready for spring. A well tuned Go Devil is one of them.
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1948 cj2a. Rebuilt L-head, steering, T90, WO 636, steering, brake lines. So far.
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Bruce W
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Posted: 26 Dec. 2017 at 10:39pm |
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I live at 4900 ft. and often drive my jeep to altitudes above 12,000. The only thing I do to compensate for altitude is to set the ignition timing about 5* more advanced than the book spec. I use the "IO" mark on the flywheel, which is 9* BTC, and set it just on the high side of the mark. BW
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It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
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3A Steve
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Posted: 27 Dec. 2017 at 1:42am |
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I live at about 900 feet above sea level. Used to be worried about carb settings. Have only been as high as 10,500 ft at Bull Creek Pass. Worked the same as at home. You probably don't have to worry about it.
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m38mike
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Posted: 27 Dec. 2017 at 8:01pm |
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Joshua, like Terry and Bruce said above, once the carb is set right to run at your home elevation, all you should need to do is adjust the timing a little to compensate for elevation. So bring a wrench to spin your distributor. I live at 8,000 feet elevation. I usually just keep my timing a couple degrees advanced and call it good for the high country. But I still carry a wrench to make the adjustment in case the engine starts running too rough. BTW, it may pay to check your plugs a couple times during the summer Jeep season to make sure you're not carboning up.
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M38Mike
46 CJ2A SAMCJ2A 4?-5? CJ2A/3A/M38 Jigsaw 51 M38 Green Jeanne 52 M38 Blue Mule, 51 M100 Blue Mule Tale 52 XM38EV1 Electro-Willys, 52 M100 Juice Box |
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Stev
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Posted: 27 Dec. 2017 at 8:28pm |
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Mike,
When you advance the timing for altitude have you ever considered using a vacuum gauge to set up the timing? Stev
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Stev
1946 CJ2A Trail Jeep (The Saint), 1948 CJ2A Lefty Restored |
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m38mike
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Posted: 29 Dec. 2017 at 2:04pm |
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Stev, no I have not. Not sure how to do it, or what to look for.
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M38Mike
46 CJ2A SAMCJ2A 4?-5? CJ2A/3A/M38 Jigsaw 51 M38 Green Jeanne 52 M38 Blue Mule, 51 M100 Blue Mule Tale 52 XM38EV1 Electro-Willys, 52 M100 Juice Box |
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athawk11
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Posted: 29 Dec. 2017 at 4:12pm |
As mentioned by Terry, the rule of thumb is you will lose 1 point of vacuum for every 1000’ rise in elevation. At sea level you hope your vacuum reading is a steady 21-22 Hg. At my elevation (5,500’), I’m happy to get 16-17 Hg. For me, this is roughly 7-ish degrees advanced. At 8,000’ you may only get 14 Hg…
Mike, most of us hook up an automotive vacuum gauge to the wiper motor port on the intake manifold. While hooked up, you can adjust the timing to maximize the vacuum reading for your altitude. Not sure where you can pull a vacuum reading out of that Pinto engine of yours. |
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1- 1946 CJ2A
2- 1949 CJ3A |
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jhg
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Posted: 29 Dec. 2017 at 4:34pm |
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Very helpful.
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1948 cj2a. Rebuilt L-head, steering, T90, WO 636, steering, brake lines. So far.
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WeeWilly
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Posted: 29 Dec. 2017 at 7:02pm |
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More years back than I like to remember there was a article (Gus's Garage) in a Popular Mechanics magazine that might be to an advantage for those changing altitudes while driving your jeeps. He used a cable, like a choke cable hooked to the distributor with the mount bolt being loose to change the timing. Gus did it to retard the timing to make a worn out engine easier to start, I miss those old magazines.
You could also hook up a vacuum gauge to the dash to adjust for the best timing at your altitude. Jim |
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47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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Ol' Unreliable
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Posted: 30 Dec. 2017 at 3:21am |
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Was Gus's Garage in Popular Mechanics or Popular Science? And why did both of those magazines have to be Popular?
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There's a reason it's called Ol' Unreliable
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WeeWilly
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Posted: 30 Dec. 2017 at 4:32am |
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Both were great magazines back in the old days when they had a lot of good articles and projects, and until they started having more advertisements and few articles.
I thought the article I was referring to was Popular Mechanics from the late 1930s or early 40s, but I could be wrong since it has been quite a while since I read it. Jim |
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47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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Steelyard Blues
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Posted: 30 Dec. 2017 at 5:58am |
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If you really want to know where you are at, data log with a wideband O2 sensor or monitor a meter. I bought one of these when transplanted my '71 Maverick with an '89 5.0 stroked to a 347. When I replace my exhaust in the 2A, I will put an O2 bung in the downpipe since I already have the sensor. I'm at 4,500' in Reno and could get much higher if I climb. I'm just curious to see where she sits.
Micah |
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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m38mike wrote: