aftermarket carb suckin fuel

[minxtrab]

i have a 74 620 pickup with 74k original miles on it a little while back i put a weber aftermarket carb on it and it runs pretty well but the problem is it suck fuel to the tune of like 19 mpg....any suggestions onwhat i can do? is there jetting that i can change ? need help i amat a lose on why this is doing this any input would be appricated

[Skib]

the webber gets less MPG than the stocker, just the way it goes. it puts out more power tho.

 

 

theres always things you can do to get better than 19 on it tho

[HRH]

You can tune the Weber to get the same mileage or better than your stock Hitachi. You just need to put in smaller jets and air correctors, but with decreased fuel/air mix, you get decreased power, which defeats the purpose of the aftermarket carb to begin with. Installing higher gears would help, but 19 mpg out of a 620 is pretty reasonable. A 5 speed swap would help also. Anything to get the rpms down. Your truck probably has a 4.375 ratio rear end. Great for torque and carrying loads, not so great on fuel economy.

 

Do you know what jets you're currently running? If so post them, if not, find out and find someone who's decent with carbs. I'd help, but I think 503 is in Oregon or something?

[wildmaninid]

I find that most webers are way too over jetted for most applications, especially 4 cylinder. If you read the weber tuning guide he explains how a weber's idle circuit controls most of the performance and fuel consumption of the carb..putting in smaller main and secondary idle jets will really cut down on the fuel suck.

 

My EMPI (weber clone) had 65/55 idle jets, i went down to 45/45 and went from around 18-19 mpg to 24 now.........

 

Bill