mpg are bad

my cj5 is only getting 12.5 mpg . 225 v6 with 3 speed and 388s . rochester carb 2 jet carb . it run good but 12.5 mpg sucks. what can i do . :evil:

 

it seems to be tuned good and the timeing is right . it is running good . maybe the carb
is not the right carb for the 225

 

the best I have ever attained was 14 with 5:38s

 

3.88s are not normal gears, either a misprint or you're not sure what gears you have.
Do you know for sure that your speedo is correct, speedometers if off are not off a fixed amount like 4 miles per hour they are off a percentage which means if yours is off say 5% then your mileage is off 5% it would not be uncommon to have 31-32" tires and have your speedo off 10%. I averaged 14.7 mpg on a fresh motor with 26 miles on it and took it on a 175 mile trip.

 

Mine does about the same most of the time. My driving habits aren't exactly conducive to high gas mileage though.

I think the best thing to do is ignore it if it is well-tuned and maintained.

 

My 70 CJ5 gets about the same with 225 t14 and 4.88 gears. Ingage overdrive and it goes up to about 16 MPG. Mike

 

If you are still running a points-type distributor the gap and dwell (as well as timing and carb tuning/maint) are important. When mine would get out of adjustment the mileage dropped considerably - from 15-17 to 12-14!

You might consider an upgrade such as HEI or Pertronix. Do a search..... much previous discussion is here. I went with the Pertronix Ignitor and upgraded the coil and wires. I did have it up to 22-23 mpg but begin to notice some preignition (I was fiddling with the weights and springs in the distributor - now back to stock advance). I now average 19-20.

Of course, this information is less relevant if you have 4.88's or have already upgraded your ignition. Good luck and let us know what you find!

 

William cj3b, what kind of JEEP are you getting that mileage with? Is it Dauntless powered? Headers? Final gear ratio? Mike

 

The one in my avatar.

1970 Jeepster - basically stock
225 - partial redneck rebuild (see 'jeepster age' thread), overhauled 2G w/original oil bath, Pertronix Ignitor and Coil, manifolds and dual glasspacks (too loud)
T-14
D-20
3.73 rear end
No lift, 235/75-15's

I drive it a little over 500 miles a week. So I track my mileage VERY carefully. I also drive at 55 and below - it helps the mileage a lot and infuriates anyone lucky enough to get caught behind me on the highway

 

it was a misprint i have488s in my jeep the speedo is off about 5mph so you are right .
thank you for all your help . i may do the hei or pertronix . thanks guys