I70 Eisenhower Tunnel

[7gen]

Not specific to a model car but I have a 76 Eldorado convertible.

I plan to do some traveling. My Quadrajet is tuned for where I live, which is 400 ft. above sea level. My trip will take me through the Rockies and the Eisenhower Tunnel, which is at 11,158 ft. I'm not spending any time in the mountains, just driving through. I was concerned about the car's performance at that altitude and talked to a fellow in Rifle who said that I should be OK. He said there is only one recommended Quadrajet jet size for 0 to 10,000 feet and that while the car will be down on power by about 1/4, I should not have any trouble getting over the pass. He suggested putting the car into D2 which should keep me in second gear all the way up and down. And when I see black smoke behind me, take my foot out of it!

Anyone been over the pass in a vehicle that is set for a lower elevation?

[James Landi]

While I have no answer, I understand your concern.  There was a time when Cadillacs had sufficient reserve power that climbing hills or running in rarified air was not an issue.  As pollution controls bogged down the engine output and computer management systems were still in the future, your worse nightmare could be realized.  I have run my 4100 powered cars over some Northeast mountains that were relatively small in size and had problems holding speeds of 55 mph.   On some roads, I'd pick up the speed before attacking the mountain (aka hill), in an effort to not overly tax the engine.  Downshifting can be problematic, especially if the engine is struggling in the lower drive range.

["Cadillac Kid" Greg Surfas 15364]

Countless new Cadillacs were delivered to the customers at the factory and driven home.  This includes a lot of them going west and crossing the Rockies.  Yes you will have reduced power at altitude, but modifying the carb for a few miles at altitude and then changing back is not really practical unless you have a couple of grand to kill as well as a day on each side of the mountains to spend.  At that, the power will not increase substantially.  There is less oxygen at altitude, consequently there can be less fuel burned, and burning fuel is what makes power.  Just get in your car and your right foot will tell you what you need to do.
Greg Surfas

[David Greenburg]

The easiest adjustment is to tweak your timing.   Use the vacuum gauge method, and set your timing once you are at some altitude, perhaps Denver, and you should be alright at the higher  elevations.  I used to do this when I was in school, driving from sea level to Colo. Springs (6000 ft.).  Once there, I would reset timing, and car would be fine even going to ski areas etc. at much higher elevations.  And that was with an AMC with a 199 six.

[savemy67]

Hello 7gen,

I once drove from Minneapolis to the West Coast by way of U.S. Route 40 through Colorado, in a Ford Econoline van with a 240 cubic inch straight six engine.  Minneapolis is 830 feet above sea level.  I had no appreciable problem driving the Ford van over Berthoud Pass (elevation 11,306), Muddy Pass (elev. 8772), and Rabbit Ears Pass (elev. 9426).  I did not travel through the Eisenhower Tunnel, as Route 40 separates from Interstate 70 before the tunnel.

Christopher Winter

[Carl Fielding]

You will have no trouble driving at that elevation. Use the lowest octane gasoline available. I think it will be 85. Plan to run the higher octane out as you get to , say 5 - 6000' to accommodate pure 85 for the climb. You needn't descend in a lower gear with your 4 wheel disc brakes. As you level out in denser air , fill with the highest octane again. You will notice less power pulling a grade at altitude. Also , you yourself will not be running at 100%  I.Q. , (ask me some time about putting my Blazer on its side just after coming up from sea level to 15,000' in the Andes - good story) , so take it easy.  - Carl

[The Tassie Devil(le)]

Boy, I noticed the difference driving my car from Sacramento to Lake Tahoe.

Granted it was a V6, but I was wondering why it was getting very lethargic till I saw the 7,000 foot elevation sign.   Going back to Sacramento that afternoon, I could really feel the difference in the added power, and cooler engine.

Bruce.

[Steve Passmore]

Strange all this about elevation, is it related to your new fuel?      In the 70s we drove from New York to San Francisco across Colorado visiting many places including Independence Pass.  It was only a hire car of the day and I can honestly say I have no recollection of the slightest trouble with the car through thin air.  There was more shock at Hertz back in NY when we returned the car with 11,000 more miles than when we picked it up.

[35-709]

Greg Surfas and Steve Passmore are right!  Low land vacationers, et al go up and down these mountains day in and day out and have for many years without a second thought, many don't even know or think about what is happening as they get to the higher altitudes.  Your engine will run richer at higher altitudes and won't have quite as much power --- fuggedaboudit and enjoy the view.

[Scot Minesinger]

Agree with all the do nothing posters.  For a one of very few times trip at high altitude do nothing. 

There is a huge difference between at 4.1 and 500 Cadillac engine.  The reason the 4.1 powered Cadillac is not as collectable as other Cadillacs is primarily low power and poor reliability - not applicable to 500 engine - the 500 engine is a major reason your Cadillac is collectable today - good power and reliable.  You  should easily be able to maintain 55mph at altitude traveling up a grade.  Back in 1976 no one would have thought to modify their Cadillac for a one time trip through the mountains, and provided your car is in good repair, you should not either.

Enjoy the trip!

[bcroe]

No problem here climbing anything with a regular road, using a carb.  I managed to
get to the summit of Pikes Peak a few times, 14,000'.  The issue there was turning
around and coming down.  The engine wouldn't idle but I needed the power brakes
and power steering.  Once it was rolling down it was OK.  Bruce Roe

[7gen]

I appreciate all the advice. Thank you!!!