Ford 302 Carburetor Tuning For Elevation and Speed

[Dave Tabor]

Hi Folks,

I signed up to do the Nevada Open Road Challenge in mid-May.

I'll be driving a Gen III Coupe with a carbureted 302 (QuickFuel/Holley).

I live and drive mostly at sea level and have the carburetor circuits well-tuned using an A/F gauge (on the dash).

This event will be between 6000-4000 feet elevation, 60 miles out and 60 miles back. I'll be in the 100 mph average speed group which puts me at 3750 rpms and well 'into' the primary carburetor circuit- assuming I'll need to make some power at this speed.

The Holley jet guidance is to decrease one jet number every 2000 feet of elevation so I'd lean the carb out 3 jet sizes according to this. I assume both primaries and secondaries.

What A/F ratio should I aim for? It's not exactly 'cruise' and not WOT either. Some level of fuel economy would be a huge plus.

Thank you for any advice. I'll be bringing a full set of jets along and will be able to do some testing in the days prior to the event.

Dave
Gen III Coupe #17
13,000+ miles

[Jim1855]

I start at 700 feet in Michigan. Have driven in & out of Denver multiple times and then into the mountains.

I don't think you'll have significant problems at 6,000 feet, a bit rich, sure, but might not be worth the time and trouble to make the jet change. If you jet it for 6,000 and then go back towards sea level you be lean. This is much more of a problem.

There are some common charts or guides for jet changes per 1,000 feet. Sorry I don't remember what the basic change was.

Jim

[Dave Tabor]

I don't think you'll have significant problems at 6,000 feet, a bit rich, sure, but might not be worth the time and trouble to make the jet change. If you jet it for 6,000 and then go back towards sea level you be lean. This is much more of a problem.


Jim

Hi Jim,

Thanks for this- I may just leave it and let it be rich at elevation. That said, I'll be trailering the car to the event and only driving it on the course from 4000-6000 feet of elevation for 120 miles, then changing the jets back when I get home.

Dave
Gen III Coupe #17

[Derald Rice]

Just leave it alone like Jim said......You are not running the unlimited class, and it's only 120 miles.

Enjoy the ride.

[MB750]

Yea, leave it be. You may notice a reduction in power but that's primarily due to the lower air density at elevation, not jetting. Sure, you can jet back to perfect but for your application I'd just run it.

[Dave Tabor]

I left is as-is and all was good.

Got 11 mpg going south (net downhill) and 10 mpg north - 62 miles each way. 100 mph average speed.

Detailed post to follow.

Dave