I'm driving my 66 coupe, 351W, T-5, 3.50 rear gear From Monterey, CA to Dayton, Ohio with a pitstop in Pensacola, FL this summer(5000 miles). I have a 650 double pumper(Speed Demon). I am touring the country and have plans to hit a few high elevation spots(Grand Canyon). QUESTION: what is the formula for jet size change per X amount above sea level? I'm starting/tuned for sea level and I found the Grand Canyon area can reach around 8,000ft above sea level. I have had bad experiences in the past with drastic elevation changes that cost me a day of travel due to low O2 levels. Thanks for any imput. See you on the road!
Elevation change:jet size change ratio?
- Thread starter latamud
- Start date
brianj5600
Active Member
Are you changing jets on the road? One Holley jet size for each 2000'. 8000ft needs about 10% - 12% IIRC, too much for lower altitudes. You can cheat a little with bowl level, but no substitute for changing jets. Altitude also changes pv characteristics too. The same engine needs a smaller pv for high altitude. Good luck, this is the one time a carb sucks.
Thank you. I will be changing jets on the road. I went out and bought a few sizes to test and tune en route.
I should be in Vegas for the weekend and on to the Grand Canyon Monday and be in Mesa, AZ for a few days before I head out to Dallas etc.
I should be in Vegas for the weekend and on to the Grand Canyon Monday and be in Mesa, AZ for a few days before I head out to Dallas etc.
pabear89
Active Member
Unless your looking for peak performance,I have made that trip and more without making any changes.
unless I was staying at a higher altitude for more than a few days.
Then it was just a minor carb tweek.
Have fun sight seeing.
PB