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High Altitude question

gordonra

gordonra

Donation Time
I have driven my Alpine from Southern CA, to SW Iowa on the southern route... I 40 to Tucumcari, then up truough OK, KS, and the SE corner of NE.... about 1700 miles (will have to add it up later) (BTW, call me crazy)

No real problems to speak of other than it wasn't running well at all through the 7000 ft areas, and some pinging.

Octane boost really helped the ping, but it just wouldn't run well without a computer to adjust the mixture.

I have to return to SoCal in a couple more days... Sure would like to take the high road through Colorado, but I'm afraid that i'll have much more trouble with 12,000 ft.

Any suggestions?

Rich
 
R

RootesRacer

Donation Time
gordonra said:
I have driven my Alpine from Southern CA, to SW Iowa on the southern route... I 40 to Tucumcari, then up truough OK, KS, and the SE corner of NE.... about 1700 miles (will have to add it up later) (BTW, call me crazy)

No real problems to speak of other than it wasn't running well at all through the 7000 ft areas, and some pinging.

Octane boost really helped the ping, but it just wouldn't run well without a computer to adjust the mixture.

I have to return to SoCal in a couple more days... Sure would like to take the high road through Colorado, but I'm afraid that i'll have much more trouble with 12,000 ft.

Any suggestions?

Rich
Click to expand...

If it wasnt running so well at 7000 ft, I would skip the Colo. route.

Now if you are running strombergs and feel comfortable tweaking the main jet adjustments, then it shouldnt be a big problem.
 
R

RootesRacer

Donation Time
BTW, if you are pinging at high altitude (and you are running decent fuel), then your timing is over advanced.
In general high altitude reduces octane requirement due to the lower air density.
 
gordonra

gordonra

Donation Time
I am running Strombergs and I'm not opposed to tweeking them. As a matter of fact, I did adjust a little trying to improve.

Other than something like Colortune, how is everyone else able to tell when the mixture is correct? I adjusted the mixture for best vacuum....

The timing could be off, but I set it with timing light, at 500 RPM, Vacuum advanced plugged. I plan to check it again before I leave.

Anything else I should check?
 
R

RootesRacer

Donation Time
gordonra said:
I am running Strombergs and I'm not opposed to tweeking them. As a matter of fact, I did adjust a little trying to improve.

Other than something like Colortune, how is everyone else able to tell when the mixture is correct? I adjusted the mixture for best vacuum....

The timing could be off, but I set it with timing light, at 500 RPM, Vacuum advanced plugged. I plan to check it again before I leave.

Anything else I should check?
Click to expand...

Short of having a wide band O2 sensor, the next best air fuel ratio indicator are the plug colors and the seat of your pants.

You may have set your timing, but the factory figure is too advanced for your engine if its pinging. Plus who knows what your compression ratio is, it could be higher due to carbon buildup, or unknown number of head skims.
You cant let the engine ping, as it can hurt the piston tops and break your top rings. Also engines loose a few percent off the torque peak just before detonation, so running an engine near its detonation point will loose mileage at best.



If you do decide to drive through Colorado, stop by, I am only a few miles off of I-70.
 
Nickodell

Nickodell

Donation Time
gordonra said:
I am running Strombergs and I'm not opposed to tweeking them. As a matter of fact, I did adjust a little trying to improve.

Other than something like Colortune, how is everyone else able to tell when the mixture is correct? I adjusted the mixture for best vacuum....
Click to expand...

Both vacuum reading and rpm (by gauge or ear) can be used for mixture tuning.
 
65beam

65beam

Donation Time
high altitude

here is a question for someone to answer . my strombergs have no mixture adjustment on them. wonder how i could best compensate for high altitude ? timing appears to be my only way. ???
 
R

RootesRacer

Donation Time
65beam said:
here is a question for someone to answer . my strombergs have no mixture adjustment on them. wonder how i could best compensate for high altitude ? timing appears to be my only way. ???
Click to expand...


You sure?

I thought even then 150CDSE carbs used on the latest arrow 1725s had main mixture screws. If the mains are fixed, then perhaps the main jet assy can be swapped for an adjustable set from an earlier model CD.

Timing is not something that needs to move much with altitude, but jetting is.
 
65beam

65beam

Donation Time
high altitude

rootes racer,
these carbs are on all of my 69's. they have no adjustments for mixture. i guess i need to dig further and find what they did to compensate for alltitude .this thought never occured to me until now .
 
gordonra

gordonra

Donation Time
Ok... Transmission is back in and the car is running again, and still running a little rougher than when I left

I checked the vacuum and it's lower than it was by a couple of inches(currently 14-15 inches), and wandering a very little bit. Elevation here is about 800 ft so I wouldn't think that would be enough to cause a problem.

So, I pulled the intake and exhaust manifolds to check for leaks... I have one of the new Manifold gaskets that Jim E. was referring to in an earlier post to someone elses thread. Sprayed liberally with copper coat and seems to be a tad better. The needle isn't doing the small wandering anymore, and the vacuum level is 16 inches.

A throttle shaft on one of the Strombergs is a little loose in the housing. Hadn't noticed that before I left, so have to see if I can bush that when I get back home.

Since the block is bored .020" over and the head has been shaved, should the timing be set more advanced, or retarded than stock?
 
gordonra

gordonra

Donation Time
Made it back alive...

Wow... Quite a trip.

Before I left for the return, I determine that the intake manifold gasket was leaking. A liberal coating of Copper Coat sealed it right up.

In addition, the timing seemed ok, but I fine-tuned it and centered the micrometer adjustment in case I needed to make any changes along the way.

The good news is that the Alpine performed well all the way with only some minor mixture adjustment required at higher elevation. The setting is much more sensitive at 7000 ft than at 400 ft. I was even able to pull out better than 28 mpg through the mountains between Tucumcari, NM and LA, when I wasn't bucking a strong headwind.

The bad news is that after changing the transmission in Iowa, there is now a slight oil leak that I didn't have before. My fear is that the new front seal on the transmission somehow got damaged....Perhaps I over filled the transmission? Crap.... Not really wanting to pull the transmission again.

Side note: The low vacuum level noted in an earlier post, remained at various low values from Iowa untill I checked at Barstow... Now it's in line with what I'd expect.

Rich
 
Nickodell

Nickodell

Donation Time
gordonra said:
I have to return to SoCal in a couple more days... Sure would like to take the high road through Colorado, but I'm afraid that i'll have much more trouble with 12,000 ft.

Rich
Click to expand...

This is a bit late, but at 12,000 ft you're going to need oxygen. Not for the car, for you! In flying, at 12K ft. or higher, oxygen is mandatory. Anoxia starts to become an issue over about 10k (depends on the age and health of the person, and whether involving strenuous exercise), and even a fit person will start to show symptoms over 12k.

Anoxia has the same effect on judgement and reflexes as alcohol, and like alcohol is insidious - you don't know that you're impared. Part of flight training in the RAF was the decompression chamber test. You sat in it in flying gear and were given a series of tests. One was a gizmo with 12 lights, and a button under each light. The lights would shine for one second at random, and you had to press the corresponding button before it went out. At sea level up to about 8,000 ft. (the height most airliners are pressurized to) it was a piece of cake; every one got 100%. From memory: At 14k the average score dropped slightly, to just over 90%, but at 18k to a miserable 30%. If your scores were much below a certain level, your flying career ended at that point.

You also had to write down a series of sentences coming through your headphones. The results at 18k were hilarious. I remember to this day looking at my notepad after we were allowed to don our oxygen masks and the sentences were repeated. For "Peace is maintained by the overt threat of violent reaction to attack" I had written an almost indecipherable "Please refrain by the odor net of violets."

Fun, but like alcohol, anoxia can kill you whether you're flying a plane or driving a car. How the hell anyone managed to climb mountains of up to 29,000 ft. without oxygen is a mystery.
 
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