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Old 03-07-2018, 11:45 AM   #1
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Location: Colorado Springs
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Edelbrock jetting for altitude

72 C10, stock 350 crate engine, edelbrock 1405, HEI.

Currently at 6000ft in Colorado Springs.

I figured out how I want to re-jet going by the plug reading and the Edelbrock adjustment chart. So my question isn't as to what jets/rods I should use.

The question is this, I am driving from Colorado Springs to New Braunfels Texas the end of this month for a road trip, a difference of about 5500ft in elevation. If I re-jet my carb now for current elevation of 6000ft, am I going to hurt the engine by doing a road trip to a lower elevation for a few days? I know it will be running a little lean for majority of the trip but do you guys think this is OK?

It says in the edelbrock manual to not worry about adjusting for altitude if you're only gonna be there for a little while. That's in reference to going UP in altitude where you'd be running rich for a bit instead of going down where you'd be running lean.

I'm not racing or anything crazy, just a long easy cruise to texas.

Would you guys mess with it now, or just leave it alone and worry about it upon returning to elevation after this road trip? I'd hate to develop a ping or extreme lean condition half way through my trip and have to mess with jetting on the road.

My only idea as to this being okay is that a 1406 comes with factory leaner jetting for better mileage, which is what I am going to match with my re-tune of my 1405. The 1406s are setup from the factory at the same elevation as the 1405, so i think I will be alright. Just looking for some opinions.
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Old 03-07-2018, 03:39 PM   #2
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Location: Orem, Utah
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Re: Edelbrock jetting for altitude

I've never worried about retuning my Quadrajets when I go to sea level.
If I didn't build it or fix it, it's probably not mine.
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Old 03-07-2018, 06:29 PM   #3
Dead Parrot
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Location: Oklahoma City, OK
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Re: Edelbrock jetting for altitude

Go ahead and tune your carb for your current location. Research how much richer you will need for where you are going. Edelbrock has a nice tuning chart in the carb manuals. Find a set of rods and springs that will get you close with whatever jets you wind up with. Don't worry about changing jets. One nice thing about the 140x carbs is a rod/spring change is a 5 minute road side task. You may never need to change anything during your trip but at least you will be ready if you notice some pinging or knocking.

I did the reverse when I went from OKC to central CO to visit some friends at 9000ft. Just made a rod/spring change during a gas/rest stop somewhere around 6000ft. Really made a difference compared to the prior trip where I didn't make a change.
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