[track73]

Back when I was living on the high planes of New Mexico, the rule of thumb was 1 degree more advance for each 1000 feet of elevation, I put my total at 40 degrees, That was with a compression ratio of 10,25 :1 and 4000 feet above sea level. Way back in the '30's and 40's Ford made their famous "Denver " heads that increased the compression ratio of the flat head V8.

[Formulajones]

That is correct. You can add more timing when high up in elevation. That's typically why you see gas stations with less octane when you're up in the high elevation towns. Less octane is required up here.

Problem I run into though is that elevation changes drastically in any direction I drive, and I frequent Phoenix for car shows and cruises which is closer to sea level.

So in my case I don't add the extra timing up here and prefer to run it where the car likes it at sea level, and leave it be while up here at 5,000 feet.

The other reason I don't change it is because the crap gas we have here, the octane doesn't increase at the gas stations down near sea level like it should. So with the quality of the gas the same (which is poor) I tend to keep things on the safe side with my tune up.

[Firebob]

Wow, this is all great information. Easy enough to add a couple degrees to the timing and adjust the idle accordingly once there. I might try open one of the vac ports somewhere and see how that effects things. Simple enough to put the cap back on if I'm not feeling it. I try not to mess with anything too involved while on a road trip away from home unless something breaks. So I'll probably leave it at that and maybe it will run just a little bit better than it would've. Changing the type of gas is interesting but I'm not sure stations around are that specific about what types they sell( maybe be I just never notice). I think the label says something like , may contain up to 10% ethanol, or something like that. I imagine that's what E10 is?

[carbking]

Probably the most important thing to remember is that you are just going to be there a week. Some temporary changes like the vacuum leak, the gasoline, and maybe a little timing; and leave it at that. If you permanently relocating, different story.

My parents loved to camp, and pulled a camping trailer all over the USA, including the Rockies, in the 1950's, 1960's, until 1970 when they purchased their first used motorhome. This was before the interstate system, and there were some pretty significant grades! Dad was pretty well prepared, and he would take with him a complete set of hoses, the usual tune-up components, and a couple of extra sets of plugs. He would change the plugs after leaving high altitudes. His major concerns were tires and brakes. Generally would put on a new set of tires before leaving Missouri, and have the brakes relined. No changes to the engine at all; and the only failure I remember was a generator in Yellowstone on a Sunday morning. And no, a generator was not in his stash of spares!

Enjoy your trip!

Jon.

[Firebob]

Sounds like good advice. The trip will be to Reno for Hot August Nights. It's a week long car fest. AutoX, 1/8mi drag races, burnout contests, poker runs, lots of cruising and generally everybody's testosterone level is kicked up a couple of notches so the inclination is there to show off a bit now and then. I suppose most everyone is in more or less the same boat though so not a big deal. It's just a bit disappointing when it doesn't respond like you know it can. Not a big issue. I'll just suck it up and deal with it as best I can.
I suppose this air density would also have the same effect if you were to dyno the car at that elevation?

[johnta1]

That's why they have dyno correction factors.

[Tom Vaught]

Originally Posted by Firebob

I suppose this air density would also have the same effect if you were to dyno the car at that elevation?

Say that Ken Duttweiller dynos a Bonneville engine at his shop in Ventura California.
Makes 1000 HP with a Vortech Supercharger (small engine class) at 18 psi of boost.

So the racer goes to Bonneville area and dynos the engine at the same boost pressure.
The absolute air density He had at sea level will be less at Bonneville even with the same Boost Gage pressure.

If you want to have the same absolute air density in the motor you will need to turn up the boost (at elevation) to make up for the lower atmospheric density (the turbo is drawing in). By compressing more of the less dense air to get the same effective amount of dense air you had at sea level (requires higher boost pressure and blower/turbo rpm.
This extra boost pressure/rpm makes more heat which makes the charge less dense. To get some of the air density back you will need to compress it EVEN more... Which is why Bonneville cars with boost run GOOD inter-cooler systems.

Tom V.

[Formulajones]

Originally Posted by Firebob

I try not to mess with anything too involved while on a road trip away from home unless something breaks.

This is why I mentioned what I've done with a couple of our cars on the AFR. I just let it run a tad rich up here, and at sea level it's just a pinch lean. A happy medium. I keep a heat range hotter plug in it most of the time, and I leave the timing at it's optimum setting for sea level pump gas.

Keep the hood shut and enjoy the car If it puffs a little black smoke up here at 5,000 feet when I nail the gas, I don't worry about it. Usually it's just the initial hit, then it clears out.

If I go to the track (which is near sea level for us) I make more effort to get the AFR spot on for best performance. But that doesn't occur all that often.

[Formulajones]

Originally Posted by Firebob

Sounds like good advice. The trip will be to Reno for Hot August Nights.

I've been to that. I used to have family in Reno and would stay with them. I had the best time at that show, it never disappointed. I keep saying I want to make an effort to buzz up there again. I'd love to jump in a car and cruise up and hang. I just hate to think what a motel may cost now though, if you could find one.