Well, if you have an old lean burn system, get rid of it. Let me tell ya sometihng...(Fire man bill
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I have writin this out before and sent it along in PM's and E-mail. This is what I did to double my mileage from that crappy running lean burn. Your results may vary, but at least you'll gain some mpg's.
After I list what I did, I'll also included what could be better.
Starting from the top, on my 360 in a '79 Dodge Magnum, I got rid of the stock air cleaner. I used an older design 340 air cleaner. It has a trap door in the pan.
2* An open filter or the MoPar unsilenced unit will do nice.
A clean element. Don't wait until it's hard to see the sun. Toss it. Get a K&N or equal for the air cleaner housing.
2* A K&N extreme top will help out more.
Tune that carb. I tossed the 360's 2bbl. in favor of a Carter 625 carb. A T-Q will do better. WHY? The 2bbl is rated at a different presure drop than a 4bbl. 625 / 2 = 312. But it's less than that. The primarys are smaller than the secondarys even though its a spread bore.
2* The T-Q is around 200 cfm.
I swapped out the 2bbl for a 4bbl. , well that means the intake was also swapped. I used a factory cast iron unit.
2* You could do better with a aluminum unit.
Even the racier RPM will work. You should just be driving in the power RPM range of the intake. A Torquer II is fine. The open plenum moves air freely.
2* If your in need of head work, stainless steel valves work very well in letting the engine breath easier. Use with a braket valve job. (Remember, the easier it breath, the less it works, the less it works, the less fuel it needs.) Another thing about heads. You could mill the head a tad to up the comp ratio. With all things being equal, except the ratio, the 9.0-1 engine will make more power than a 8.0-1 engine. Since it's not really working any harder, the higher ratio creates more power on the same gas.
If you don't mind paying more for a gallon of gas, keep the increase small.
Or you'll be looking at the next octane rating higher.
On the Magnum, I stayed with the manifolds. I just upgraded for dual exhaust. A pipe @ 2-1/4, "H" pipe was used.
2* "X" would probably out power it.
Free flowing mufflers top it off. (At the time, I needed to run exhaust manifolds and cats.)
2* Headers will add power and mileage.
Just don't go crazy on pipe size.
Ignition. A swap of the lean burn unit, that does not have vaccum advance or mech advance. (Because the computer controls it. And once I removed my computer, miles fell like a rock, father than what I descibe below) To a junk yard unit and MSD 6 box and wires. Open that plug gap up per instructions and keep going till it misfires or power falls off.
This is a cheap easy way to upgrade massively for cheap.
2* I noticed that a Jacobs unit reallly kicked butt in my wifes Hyundia Excel. It was a 4cyl, 5 spd o.d. tranny. This little 4 door got 36 MPG's out the showroom floor. Looking for a bit more, I bit the bullet and purchased a Jacobs Pro Street unit. My mileage went to 40 mpg's.
The problem with this unit is that it is so powerful, it would eat plugs and distributor caps. Then again, the caps were crap with aluminum tips and such.
On your MoPar, make sure you get a good brass tip distrib cap.
I swapped out the regular fan for a viscous unit.
2* You can do better with an electric fan.
Make sure your rad. flows well and that thermo stat is opening. You can run a cooler temp unit.
Tranny, fresh fluid. (The pros say synth oils help.) I ran a cooler after the stock rads cooler. A simple sift kit helps life. Trannys like to run cool and shift fast. Not the opposite even though the factory does this for comfort.
Rear gears....A little expensive to change them, it dosen't quit pay off unless your ratio is really high. But you probably have 3.23's or lower.
A taller tire helps the Hwy. driving while a smaller one makes around ton city driving easier.
Make sure your tire pressures are where there supposed to be. No half flats.
I ran taller tires than what came with the car. No gear change. They were 2.76 gears.
These mods on my '79 Dodge Magnum got me from a scary 10 MPG's on the Hwy.
YES 10 big whoppin ones!
All the way to 20 MPGS on the Hwy at a reasonable cruise rate.
I never got to headers or a cam swap.
All the first suggestions were the ones I did to the car. Nothing else. The (2*) is an upgrade suggestion
No go reclaim whats yours!