The 307 only has about 150 horsepower. It weighs at LEAST 4300 lbs. Most likely it's got a 2.93 ratio in the rearend and possibly the TH2004R overdrive transmission. This combination sucks for FE because the motor is chugging gas trying to move all that weight around.
I would _not_ swap the 7A heads from the '85-newer 307s. They got smaller intake and exhaust runners so they don't flow too well, and you'll need to swap the intake manifold as well because if you run the older intake with the 7A heads there will be a port mismatch. Don't swap in the camshaft either from the later motor, it uses roller lifters that are physically larger and will not fit in the older block. The '85-later 307 Ys made 10 less hp than the earlier engines.
I would not change to a numerically lower gear ratio in the rear axle either. It'll lug the engine even more.
Like others have mentioned here, the cheapest things to do would be to air the tires up, give it a good tuneup and drive it gingerly. Add a vacuum gauge. I would not drive around in overdrive in the city. With the torque converter locked, and transmission in overdrive with a 2.93 rear gear ratio, your overall gear ratio is 1.96:1! Great if you're on the Bonneville salt flats but not good when you're driving in the city.
I would change the gear ratio in the rearend, honestly. 3.23 or 3.42 was the highest numerical gear ratio available. I'd put 3.42s in and have the speedometer corrected. If the vehicle is computer controoled, the speedometer will rear incorrectly until this is addressed. The vehicle speed sensors on these cars are usually behind the speedometer. It'll cost more than $100 of course but it'll be like night and day.
If the engine has a cast-iron intake manifold, you can replace it with a factory aluminum casting. It will shave some weight off the front end. It'll have an A4 cast between the front water passage and the #2 intake runner, which is on the left side of the intake manifold to the left of the thermostat housing. Look for aluminum hoods, some were used on diesel-equipped vehicles.
Got $1000 to spend and don't want to buy a different car? Put a Olds 350-403 in it. Guarenteed to get better performance and fuel mileage. The Olds 403 has at least 310 lb. ft of torque vs. the 307s 250 lb. ft.
Honestly, I say replace it with an Chevrolet Astro. Seats 8, hauls plywood sheets, I've always been able to get 18 mpg out of the 2WD versions, fairly easy to repair, and you can find decent '96 and newer vans for less than $2000.
Well, since others have already bumped this old thread...
Originally Posted by spazzer
It weighs at LEAST 4300 lbs.
Are you sure? My 1980 LeSabre Limited V6 "coupe" (I use that term loosely here; it's officially called a coupe, because it has two doors, but IMO it's more like a yacht, which I really enjoy) has a reported curb weight of ~3400 lbs, IIRC. Maybe it was 3500, I'll try to remember to check the manual when I get home. Would the wagon be 800 pounds more, or would it have gotten heavier between 1980 and 1982?
I'd guess the $100 would be enough to get fuel injection working with a junkyard TBI, but I don't know if that would help.
Yes, it is a 4,000 pound car, almost exactly, and it has had alot of work done on it, carb has been rebuilt, valve job, new cat, tranny flush, it could use new tires, but they are the narrowest that will fit the 15" wheels that I could find.
Not sure on the total number of winter miles that it was used, but now that spring is here and alternent side parking for snow plowing is not in affect she is leaving the car and ridding her bike, or walking, selling it "is not an option" we've settled on mocking each other for our cars, mine is little and green and the station wagon is not...