MotorCraft 2150 Altitude Compensator

[Kokopelli]

Does anyone have experience with a 2150 that has an altitude compensator. My 75 with stock 302 except for headers and exhaust came from sea level and is not loving the altitude at its new home, 5500'. I typically drive it between 4500-7500 with occasional drives over 9000'. It is running super rich and has a hesitation. Has a reman MotorCraft 2150 from AutoLine. Going to rebuild it before i work on dialing it in and have seen some spec sheets and mentions of an altitude compensator that was sometimes installed on the 2150. Wondering if they work well and it it would be worth my time to try to locate one and add it during my rebuild.

 

[73azbronco]

https://www.carburetor-parts.com/21...9OkPFoQO7Qi3ftxoPmP8824TTt-Heg8wMZP-cx6FWl5zg

be real sure this fits the 2150 on a bronco. I know one barrel for 6 cyl are bronco specific. The schematic shows carb for 3.8l engine thats a 230ci engine.

 

[DirtDonk]

Why not just start by leaning out the main jets a few sizes? If you don't need it to run perfect at altitudes down low anymore, then just tune it for the high-altitude.
I'm sure the altitude compensator was some sort of fix for something, but perhaps just a re-jet will get you where you need to be.

I'm sure the old-timers here are tired of hearing my old "cure" for high-altitude running, but it did work very well for me.
I introduced a sort of "controlled vacuum leak" by using the wrong PCV valve. Picked one up for a mid-'70's Granada with 302 and it made it run very lean under most conditions.
When I'd go up into the Sierras, and we stopped somewhere for food or gas once we were above 3,000-4,000 feet, I'd pop the "wrong" PCV valve in the system and toss the normal one into the tool box for the trip home.
Worked great for many years. Certainly not a perfect cure, and maybe, being a PCV valve after all, it did not compensate under all conditions. But it sure beat the heck out of changing the jets for a trip!

Another "semi-tried and true" method used back in the day was to plumb a mechanical valve into one of the vacuum lines or fittings. Open it ever so slightly as your altitude increases, and control your own vacuum leak.
Of course, you don't want this in a single running or hose. Better to put it into the common plenum area, or right into the PCV line itself.

Sorry for waxing nostalgic, for simpler times, but there might other options for you in the short term.

Paul

 

[Kokopelli]

Why not just start by leaning out the main jets a few sizes? If you don't need it to run perfect at altitudes down low anymore, then just tune it for the high-altitude.
I'm sure the altitude compensator was some sort of fix for something, but perhaps just a re-jet will get you where you need to be.

I'm sure the old-timers here are tired of hearing my old "cure" for high-altitude running, but it did work very well for me.
I introduced a sort of "controlled vacuum leak" by using the wrong PCV valve. Picked one up for a mid-'70's Granada with 302 and it made it run very lean under most conditions.
When I'd go up into the Sierras, and we stopped somewhere for food or gas once we were above 3,000-4,000 feet, I'd pop the "wrong" PCV valve in the system and toss the normal one into the tool box for the trip home.
Worked great for many years. Certainly not a perfect cure, and maybe, being a PCV valve after all, it did not compensate under all conditions. But it sure beat the heck out of changing the jets for a trip!

Another "semi-tried and true" method used back in the day was to plumb a mechanical valve into one of the vacuum lines or fittings. Open it ever so slightly as your altitude increases, and control your own vacuum leak.
Of course, you don't want this in a single running or hose. Better to put it into the common plenum area, or right into the PCV line itself.

Sorry for waxing nostalgic, for simpler times, but there might other options for you in the short term.

Paul

Paul.

Yep I plan to re-jet during the rebuild. Love the quick and dirty PCV valve fix. The altitude compensator, as I understand it, basically works the same way, its just a valve controlled by atmospheric pressure and opens slightly as you go up in altitude to lean out the mixture.

 

[DirtDonk]

While I've heard of them forever, I can't say I remember ever seeing one in person. Probably because I spend most of my time at sea level!
Be interesting if you can find one.
Of course, I remember my first trip to the Sierras with full EFI vividly! I remember passing altitudes that would just chug my old cars down, and not even feeling it!

I just had another thought. Were the headers installed by the previous owner(s) or by you? If previous to your buying it, it's also possible that the PO installed even larger jets to compensate for the better breathing. That would bode even richer running for you, even with the headers I would think.
And how is the exhaust? In good shape?
Next time you're under the hood (and have some time and initiative on your hands!) pop the top off of the carburetor and see if you can see the markings on the jets as to their size.
Popping the top off, without having to dismantle much more, has always been a nice part of owning Ford 2bbl carbs. I once actually ran my '83 F150 without the top of the carb on it while I was diagnosing a running issue.
It was the "slightly electronic" version of the carb, and it turned out that the bleed valve on the back (maybe the same as what we're talking about for yours?) had deteriorated and failed. I plugged the hole because I did not immediately find a replacement part, and the truck ran fine after that.
But the point I was beating around the bush on, was that it was extremely interesting to watch the inner carburetor workings while the engine was running. Since that particular carb had the floats attached to the lower body, you could watch the fuel level in the float bowl go down, then back up as the fuel entered from the pump. Pretty cool stuff actually.
Of course, your normal safety precautions take on an even more important aspect when you're literally exposing gas to the air while the engine is running!
In other words, don't also test your ignition for spark by holding a plug wire close to the carb!

Paul

 

[73azbronco]

altitude compensators were a way to help meet emissions more than make it drive good. They also added complexity ensuring you needed a tune up every year.

 

[m_m70]

I'm sure the old-timers here are tired of hearing my old "cure" for high-altitude running, but it did work very well for me.

ands still works!