How I made a 20% increas in FE on my carb'd Mustang
 

I had been driving my Mustang for a year, getting disappointing numbers. I always keep track of fuel economy, even though I am resigned to the fact that you don't drive what I do for fuel economy. Still, a few things helped me along.

1. The carburetor. It was tuned on the safe (rich) side when installed. The black soot that collected at an alarming rate on my tailpipes was my first indication; carbon holding valves open was the final straw. One stage leaner on my cruise metering rods did the trick, I now have far less soot buildup, no carbon problems, improved FE, and all while retaining driveability. I also reset my lean-best idle, and it's a smidge leaner than before.

2. Driving style. I've hypermiled other cars before, so I'm no stranger to technique, but figured on a carb'd car with no aerodynamics and an auto trans it was a lost cause. I realized I was looking at it the wrong way; poor aerodynamics, for instance, mean that slowing down can net great benefits. My commute consists mostly of 50 mph routes, with one section at 45 and another at 55. I slowed down to 40 and redoubled my efforts to be smooth on the throttle and take advantage of any coasting.

3. Tyres. I had them up to 35 already, which was the sidewall max of my old tyres, and just recently jacked them up to 38psi cold on my new Goodyears with a 44psi sidewall max.

Results? I went from high-13's/mid-14's to over 17. In the last month, every tank has been over 17mpg (except for two tanks, while travelling, with extenuating circumstances - I filled up quickly after so they wouldn't "contaminate" a longer tank), with several over 18 and a first tank over 20mpg. My commuting tanks, the ones that really count, are consistenly in the mid 17's now. Assuming a conservative 3mpg gain (I'd say it's closer to 3,5), that's a 21% improvement. Hooray!

Good job :)
My '67 Mustang only get 6-8mpg :D but it's not for commuting anymore...

Have you thought about some "vintage" like mods??? Possibly lowering it, a Trans-Am road racing style air dam or even a clear lexan grill block might help tremendously. I'm sure there are a lot of things you could do that can be hidden so no one knows, like a rear belly pan to smooth airflow out the back of the parachute like rear bumper valence. A more extreme approach would be going with an AODE trans to get a lock up torque converter, that by itself would help mpg quite a bit.

Thanks! I like some of the aero mods. I've looked many a time at the front of the car and thought my lower control arms looked like a real aero hog and wondered the same about that rear axle. Never thought about the rear valance though. The car's lowered 1" from stock already, and an AOD is on my list of things I would LOVE to do someday - on more than $7,84/hr pay :(

I've toyed with the grille block idea in winter. It runs far too hot in summer for one, but in winter I think it has possibilities. I can imagine that it would smooth out the airflow into the snout as well...

You can block the grille and add a lower scoop to retain adequate cooling.

What I really need for cooling is to have the radiator rodded out. Sitting for two years helped nothing on this car.

Get a big block radiator, or just find an appropriate one made more recently to get more cooling in less space. Another mod that would help out is to get rid of the egine driven fan and convert to electric. I know what you mean about cooling issues. I have a big block radiator and I still had overheating issues in the summer, while in traffic, those old rediators just aren't as good at radiating as more modern ones. I think you could get away with an almost full grill block and electric fans. Just duct under the front bumper and you ought to get enough air flow to keep it cool on the road and the electric fans will move air much better in traffic than that old mechanical one ever could.
Have you considered taller rear gears? I think you could go up to 2.43 and then be cruising at 1000rpm down the highway. That can be done for less than $100.

289 v8?

Theres a lot you could do.

We put in a brand new 3-row radiator when the engine was rebuilt in '02, and it always ran at 160* (the temp. of the former t-stat) even during summer. This radiator, IIRC, was rated for the 390 big block; the original-size radiator was puny. Can't remember though exactly as I was 17 and I didn't handle the business on this car back then. When we moved to Texas, it sat for two years and we've had cooling issues ever since. Texas isn't that much hotter than where we moved from for us to be having cooling issues now, all of a sudden. So, I'm thinking that sitting for two years is what did it. I can see buildup in the rad and the coolant I flushed out when I started driving the car was a rather nasty rust tone...

The idea of taller rear gearing occurred to me, but as I'm going to run an AOD eventually with 3,50:1 gearing in the back, I don't want to swap rear gears twice. It gets a little doggy with those tall gears too, I had a '68 in high school with 2,73's and though they aren't much taller than my 3:1's in this car, it was noticibly more sluggish. If I found a good deal on some 2,80's, which was a stock available ratio in some 8" rear-end Mustangs, I might think about those, though; the guys on allfordmustangs.com and StangNet can pull 22-23mpg highway tanks with those.

bhazard, it's the original 289 block and heads, with a stock cam, but on rebuild the machine shop went ,040" over (without telling us!) and we tossed in a 302 crank since they're cheap. She displaces 308ci now.

I poured some vinegar in the radiator of my tbird and have been driving it around like that for about a week now. I had the plastic reservoir pretty clean before that and now its got all kinds of sludgy crap in it. I think before too long im gonna blow everything out with the hose and fill it with straight water and about a gallon of vinegar (less than $3) and run it for a few days like that and see what comes out.

I think vinegar makes a nice cheap cooling system flush.

Not bad...I may try that. The last bottle of flush I had didn't seem to do much, I like the vinegar idea much better. Does it lube the water pump well enough?