High Altitude carb carburetor tuning

[partsloco]

Below is a video I made to help people better understand high altitude carb tuning.

https://www.youtube.com/watch?v=eF05KpuAOCs

 

[dmplatt]

Thanks for posting this. Admittedly a little over my head, but interesting nonetheless. My house is at 4400' and a recent trip to about 10,000' was interesting. Basically no power toward the top of that hill and this would explain it!

 

[Bronco DLight]

Wish I had this last summer. I have the stock MC 2100. Took my '74 from sea level to 10,000 feet and it went from strong to pitiful. I couldn't get anyone to change the jets. After three mechanics in two weeks, I watched online how to change the jets and ordered some. Problem was, one of the jets was stripped. I changed one down three steps. Four cylinders ran well while the others fouled plugs within five miles. Finally gave up, bought a '98 explorer, and am trying to get the conversion finished so I can tell myself that it was all worth it. I would have simply bought an edelbrock carb and gone your route had I known they were good for altitude and much easier to convert. Thanks for the info.

D

 

[Chief Master Sergeant]

Man, I tried three different carbs and every jet combination known to mankind to get mine to run right with a carb here in Albuquerque. Finally said, "Screw it" and went EFI.

 

[Zdo]

I'm thinking of a Quadrajet. Would this adjust automatically or do you need to change parts on this too?

In Denver so I can go from 5000' to 10,000'.

-Doug

 

[jckkys]

The Qjet has metering rods like the AFBs but are not easy to change. Some 2150s in the late '70s have altitude compensation built in. These are easy to find in mountainous state's junk yards. Even without compensators, the 2100-2150-4100 are fairly tolerant of altitude changes. But I like the AFB when driving north through Az. 500' in Phx goes to 7000' in Flagstaff. It's hard to beat the ease of changing rods and and step up springs by removing 2 screws. The Edelbrock owner's manual even spells out what rods and springs to get. Smaller changes' like going from below sea level in El Centro up to 4200' in the San Diego Mtns. and back down to 0' on the coast, are no problem for carbs.

 

[71broncman]

Thanks for the informative videos. I've done all the mods mentioned except for the regulator. Guess I have a little more money to spend, but it sounds like it will be worth it.
Mark.

 

[boomeroid]

Soooooo, it was mentioned in the video that Holleys are a PITA. Is that true of their Truck Avenger too? Anyone have any experience with those? I live in Reno at about 4500' and I will cruise the Sierras regularly.

 

[dao1980]

Man, I tried three different carbs and every jet combination known to mankind to get mine to run right with a carb here in Albuquerque. Finally said, "Screw it" and went EFI.

Sure do miss Albuquerque.
I lived in Cedar Crest for a small while and noticed my little Toyota truck behaved way differently up there than it had back here in Chattanooga.

Heck, driving up to the peak on 37inch tires made that little 4cylinder really work.

 

[Chief Master Sergeant]

Sure do miss Albuquerque.
I lived in Cedar Crest for a small while and noticed my little Toyota truck behaved way differently up there than it had back here in Chattanooga.

Heck, driving up to the peak on 37inch tires made that little 4cylinder really work.

Yeah, I really like it here, but we're retiring and moving on.