Stock 1987 Formula LG4 115,000 mile motor gets about 150-160 miles out of a tank o gas. Car runs around 200* driving and 220* in traffic. Thought the 700r4 and the 2:73's would help out tremendously but I am dissapointed.

So far I have:
-Changed fuel filter
-added K&N air filter

BTW, How big is a 3rd gen's gas tank? I know the 80 has around a 20 gal tank and I get better mileage with a 350/TH350, 3:42's and only 14 valves workin!

 

I would check the simpler things first; make sure that the choke isn't sticking and that the distributor's vacuum advance operates OK. Also initial ignition advance setting.

If you're doing most of your driving in the city perhaps you shouldn't expect much better mileage, mine is much the same as what you're getting.

 

carbed 3rd gens, 5.0's where about 16.3 and EFI where 15.5

 

Doesn't that pretty much define your problem?

You can't expect good performance out of a machine that isn't healthy.

FWIW, my donor car had 123,200 miles on it when I pulled the drivetrain and installed it in my car. It had 143,600 when I did the mods in the sig. It now has 153,900 on it, and I got 16.7 mpg the last fill-up (and I had not babied it during that tankful). Before the mods, it would get 18-19 mpg on a regular basis, and that was before the torque converter clutch lock-up was functional. It has run on 8 cylinders the entire time I've had it.

 

Also to calculate how much do you fill up the tank after your 160miles

is it 10 gal or 15 gal??

For reference my car not quite tuned yet with 3.73 and T-5 gets about 180-190 miles on 13 gals

and lets just say I got the car about a month ago and Im still enjoying it

I would change your plugs/cap/coil/rotor/wires, if they haven't. Also get a tune up on the carb check all your vacuum lines and replace any brittle or broken lines. check your O2 sensor (CC Carb yes?) and replace it if it is original.

With that change your fuel filter as well.

 

The 80 Z28 is the one that only has 14 working valves.....that's why It's getting a transplant soon.


The plug wires on the car look to be the original ones and I doubt that the o2 sensor has been changed. On that note, I don't even want to think of what the plugs are gonna look like. I 'm just gonna have to go through and change all the little parts and give the 'ol girl a tuneup.

thanks
denis

 

A stock '87 LG4 won't have a vacuum advance. I do agree with checking the ignition timing, though.

denis, you had me confused with your switching back & forth between vehicles (try using the clutch when you do that ).

From your original description, I assumed that the vehicle was basically well-maintained and tuned. Obviously, that either isn't the case, or you at least don't know if that's the case. Do the plugs, wires, timing, fuel filter, oil & filter, etc., see if that makes a difference.

To calculate mileage, keep track of the odometer reading when you fill it up, then divide the miles driven by the gallons added to fill the tank the next time (I have that data for the Camaro for each tankful since Aug '99). This stuff of "miles per tank" is pretty much useless, since the gallons remaining when the gage hits "E" can vary quite a bit from vehicle to vehicle, and from gas fill to gas fill. Give us some real data to work with.