Taking a V8 Edlebrock rig from sea levels to CO mountains (1 Viewer)

[tdskip]

Good morning and very belated Happy New Year (just sneaked that in under the wire).

My co-driver and I have been invited to a CO mountain trip this August and I’m curious about what I need to do to get the carb / engine to be happy at altitude.

The rig handled northern AZ just fine but CO driving will be well above that.

I know we have some forum members here so hoping to get some coaching.

Thanks!

 

[SteveH]

Carb or EFI? If the latter, then no problem.

It will tend to run rich and you will want to advance timing a bit, which will bump up your idle speed. If your idle mixture screw is handy, you might lean it out a wee bit (keep track of the turns so you can set it back).

At very high elevations (12K feet), I suspect you will see small black clouds of smoke at times and it may stall. For a day or two, this may not matter, but extended high elevation operation might require rejetting. My stock FJ40 has sea level jetting and it ran ok at 12K feet, but was low on power and not very happy about it.

Beyond all that, be sure all other stuff (cooling system) is solid and can handle low-speed 'wheeling.

 

[pjohnson]

Sniper

 

[melvinjo]

We are the same: I have a 350 plain jane in my FJ45 that had an ebrock. Bottom line, if you plan to hit the high ones in Co, you will never get your ebrock right for the high passes, like 10,000 or higher. And I take my FJ on some of the highest peaks and passes in Co.

I have the FI tech on my FJ and my 71 Cuda Easy install, super reliable

 

[tdskip]

Hi guys - it is a carb now. Will be about a 4 day trip so needs to be reliable for that time period.

Was thinking Sniper EFI as well, which isn’t a bad thing to have anyway, but don’t want to just thrown money at it

 

[pigmony]

I've got an Edelbrock carb on a pretty vanilla GM 5.7 liter. I live at about 5,000 and play at 7-8,000. I make some adjustments by ear when I start to feel it performing poorly. I feel like 3,000 feet shouldn't make as much difference as it does on my rig. I don't have tons of carb tuning experience, so I don't know if my situation is a result of how my carb is tune and my particular setup, if that just how they are, or if my particular carb just needs a lot of attention.

 

[pb4ugo]

I live in the midwest at 500ft above sea level and have wheeled in Colorado, 2 weeks at a time, several times. I run a sbc with a qjet, but It really doesn't matter the make of the carb. The only adjustment I ever made was to advance the timing.. I only made the adjustments when my idle became really low, and advanced the timing to get back to a proper rpm. On trails where we started at around 7k ft and went to 12 or 14k, I recall making an adjustent during the climb. If a carb is jetted to sea level and then going to Colorado, it's going to run rich and be sluggish. The last time I was there, I also limited the power valve movement to try to lean it out some. The other adjustment I made was lowering the air pressure in the tires as I went higher in elevation.

 

[DangerNoodle]

Being from Colorado, it really depends on where you are going. I live at 9000 feet and will easily go up to 12,000-13,000 feet on different passes. I don't have a whole lot on advice besides bringing extra jets if you do end up needing them. It's a lot easier to have them instead of trying to limp around. Carbs will handle the elevation changes, but if you are coming from sea level up here, you might have to jet. Most of my experience comes from dirt bikes, but, not stalling at higher elevations is really helpful. The higher you get, the harder stuff is to get started if you aren't tuned well. You might want to talk to @cbmontgo about his experiences with his cruisers up here.

Some other stuff for elevation.

Drink a lot of water. Like more than you think. You get dehydrated up here really easily and it hits fast. The air in CO is amazingly dry. It's really not much fun either. If you have the time to get acclimated, great. if not, you may want to look at getting a couple of O2 bottle from any pharmacy around here. I've had people that come up from lower elevations really like having them around and boost their O2 levels occasionally. I've also had people get altitude sickness, so be sure you know the symptoms and what to do if someone does get it. It would really suck to have on a long drive. Also, if you are going up into the mountains, be prepared. I don't know if your rig has a top or not, but it can be cold, extremely windy, or get stormy really fast here. Bring extra layers and be ready.
This is how windy it was on the Loch Lomond Overlook last year. It blew over a couple of our dirt bikes on the kickstand side.
Just be prepared.

Anyhow, have a great trip.

 

[cbmontgo]

In my opinion, if you have a well-tuned carb at sea level, you will be okay at elevation for a short trip. Of course, you will notice a significant reduction in horsepower (~3% for every 1000' elevation) and some smoking, but there's no getting around that up here.

Once you arrive, you might find that your idle speed is low, so I'd probably adjust that before adjusting timing. I don't know the Edelbrock carburetor, but the principle should be the same.

I wouldn't mess with rejetting, as that can be trial and error with different setups and you might spend your whole trip swapping jets back and forth instead of taking in the scenery.

Vapor lock is another bit of collateral damage with altitude, so just be patient with that unless you have an electric fuel pump or another means to mitigate it.

Those are my thoughts, living at 9,100' with carbureted rigs.

 

[DangerNoodle]

In my opinion, if you have a well-tuned carb at sea level, you will be okay at elevation for a short trip. Of course, you will notice a significant reduction in horsepower (~3% for every 1000' elevation) and some smoking, but there's no getting around that up here.

Once you arrive, you might find that your idle speed is low, so I'd probably adjust that before adjusting timing. I don't know the Edelbrock carburetor, but the principle should be the same.

I wouldn't mess with rejetting, as that can be trial and error with different setups and you might spend your whole trip swapping jets back and forth instead of taking in the scenery.

Vapor lock is another bit of collateral damage with altitude, so just be patient with that unless you have an electric fuel pump or another means to mitigate it.

Those are my thoughts, living at 9,100' with carbureted rigs.

I thought that you might have some better advice than me. I seem to be correct.

 

[Tancruiser]

When you fill up the tank you can find non ethanol gas around here I would recommend it.

 

[Downey]

So back in the day when I use to run a Holley 350 two barrel in my old Chevy V8 Pickup the truck had pure black smoke pouring out the tail pipe above 6,000 ft., and the truck (with empty bed) pulled the hill from 6,000 ft up to my cabin at 7,000 ft. so poorly that I almost had to shift it down from 2nd gear to first gear. Then I learned about the Holley dual stage high altitude power valves, installed one, then I pulled the same hill (with full load of sheet rock) so fast that I almost had to shift up from 2nd gear to 3rd gear going up the same hill. Bottom line- - -these dual stage power valves give you a screaming hot rod above 6,000 ft. Take a gander at ebay #302206913478 and #292011120459.

 

[tdskip]

Thanks for all the input. She runs great where I am and did fine near Flagstaff and up to +/-8100 feet.

 

[Dizzy]

When I first fired up my 2F, I could pull a vac cap on the manifold and I would get a audible boost on the idle rpm! I know that shouldn't happen on Mud because Aisan's are near perfect, second only to EFI, but there is no air here.

If there is one driveability adjustment to a carbed engine to make at altitude, barely bump up the idle speed screw to open up the throttle plate (and count how many partial turns you made so you can return it back). When I drive my Weber carburetored Nissan 20 miles from 6,800' up to 10,300,' I get a rougher idle at a lower speed because the engine is starved for air. Don't worry about being too rich, it won't damage your motor for a vacation.

 

[4x4veteran]

I have pulled a 16 foot travel trailer with my 1970 FJ40 over a lot of the U.S. when it had the stock six and later with a stock 350 with 2bbl.
I lived at 5500 feet in high desert and had the 40 in both configurations from sea level to ten thousand feet or better in the sierra's with no problem.
Just have a good well tuned engine and good gas and you should have no problems.

 

[tdskip]

Thank you for the great discussion, very much appreciate the feedback and experiences.