Seekeroflight
Garland
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Many moons ago I remember my dear old dad saying something about cars in Colorado having their carborators adjusted differently than those of us in lower altitudes. And I remember our car being a bit sluggish and dear old dad saying that we won't do any modifications. Besides we'll only be here a couple of days and gasoline being at 25 cents a gallon - who really cares.
Back to the present: The last trip my DW and I took through the Smokey Mountains of the Carolinas had our '95 Allegro huffing and puffing. While climbing some of the steeper hills the Chevy 454 would even miss and seemed terribly underpowered. One rather steep hill off of the beaten path outside of Maggie NC the Allegro simply refused to climb. We turned around put it in low gear and pretty much rode the brakes back down into town.
Do I need to adjust the air intake to allow more air into the mix when in higher altitudes? It's been a long time since I've tinkered in a carborator but if needed I can refresh my memory.
We're planning a trip this summer into the Rockies which are even higher so I'm expecting more underpowered travel and wasted gasoline unless something is adjusted, fixed or otherwise done.
Suggestions?
May you live in interesting times,
Seeker Of Light
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wallynm
Los Alamos NM
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95 my guess is TBI so I suggest new plugs, new plug wires, new air cleaner and have the computer checked.
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sc3283
St Louis
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your engine is controlled by a computer. The computer does all the required adjusting on it's own. All you can do is be sure the state of tune is proper and that is all
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Jumbo One
Seattle
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Don't forget the fuel filter(s) if they haven't been changed for a while...
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Gale Hawkins
Murray, KY
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We found 14+ grades in the east and the west with our 1992 454 TBI but never stalled on one but would have if it had not been serviced properly.
In first gear there is next to no reason to use the brakes going down the same grades we have found unless it gets to pushing us 25-40 MPH then a quick jab does the trick from time to time but we are only at about 15K pounds.
Maybe your compression rings are shot or you have some burn valves?
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rgatijnet1
Florida
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They will adjust the gasoline for you out west. You will find 85 octane fuel(instead of 87 octane regular), which works fine in the high altitude. It used to be that people would change the fuel jets in the carb to offset the slightly lower oxygen levels at high altitude. This is sort of a pain to do unless your vehicle was going to stay at that altitude for a long period of time.
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WyoTraveler
Northwest, Wyoming
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YUP, we use 85 octane. Works fine in my 6.8L V10
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Snomas
Denver, CO
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When I had a gasser w/ the chev 454 it would always burn the plug wires and start missing. A common problem with their set up near the exhaust. I drove mine all over the rockies w/ no problems as long as it was well tuned!!!!
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Daveinet
il
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There is more you can do even though the engine is controlled by the ECM. While the computer does sample atmosphere, it can only do it at idle. If you make a long run, where you gain more than 1000 feet without letting off the throttle, the computer will not update and compensate for the altitude change. So, if you momentarily let off the throttle for a second or 2, it will give the computer a chance to sample the atmospheric pressure. The other problem with running wide open, is that you are in mixture enrichment mode. This means that it is not sampling the O2 sensor, and is adjusting the mixture based the most recent time when it was not in enrichment. So the engine could be running very rich, and the computer would not know it. One other thing is that the timing retard is very aggressive for that ECM. This means as you step on the throttle, the ECM retards the timing drastically. (technically, the timing is not retarded, its just that it takes out some of the advance) You can have the ECM chipped, so they do not take out so much timing. But the main thing you can do is just manually move your distributor by about 4 degrees. If you are somewhat of a computer type, you can cheaply connect a laptop to it, so you can watch the knock sensor and be as aggressive as possible with the timing. Also any thing you can do to the intake to help the engine breath will make some difference.
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Mike and Trish
Southern Delaware
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rgatijnet1 wrote:They will adjust the gasoline for you out west. You will find 85 octane fuel(instead of 87 octane regular), which works fine in the high altitude. It used to be that people would change the fuel jets in the carb to offset the slightly lower oxygen levels at high altitude. This is sort of a pain to do unless your vehicle was going to stay at that altitude for a long period of time.
Lower-octane gasoline is not necessary or helpful at higher altitudes; it's just cheaper, and blended that way because that's as high as it needs to be in the thinner atmosphere. Vehicles that run well on 87 octane at sea level will run just as well on 85 octane in the Rockies.
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