Oregon Rodder

I've got a '72 Grande coupe that I have been doing some restoring on. I had the 351-2V Cleveland rebuilt to stock specs. The car has the FMX auto trans and unknown factory rearend ratio. I have a couple thousand miles on the engine now and though it may still be a little tight I think it runs pretty normal. Question I have now is that I'm only getting about 10-11 miles per gal. even on open road travel at normal highway speeds. Does this sound normal for this drivetrain combo?

67mustang302

Have you tuned the car properly? And it's going to depend on how you drive and what rpm it cruises at as well.

I wouldn't expect a stock Cleveland to get great mileage though.

1971mach1

As said, don't expect the Clev to get great MPGs, but you should
see at least 15 hwy. What rpm are you cruzing at 60 mph? That will
give some clue to which axel ratio (depending on tire size). Advancing
your timing will give you better MPGs, but don't go too far or you'll
start pinging. You can advance farther with premium gas and get better MPGs.
Check to see if your vacuum advance is working. Tune-up, as mentioned, will help as will new air filter.

REAVER117

Sounds a little low, but the '72 was a big car and the FMX is HEAVY so it's within reason. I would step up to a 4 barrel carb, you should get better gas mileage (unless you have a lead foot) because of the smaller primaries. Otherwise you may just want to tune the 2 barrel carb.

Starfury

I agree, tune the carb, adjust the timing properly (both static and dynamic), and it may improve a little, but that motor in that car with that transmission makes for a gas hog.

THUMPIN455

A cam swap would help, as well as a 4 barrel carb and intake. But barring that, you need to make sure your carb isnt leaking fuel somewhere. The 2V I had on one of the F150s sucked gas like mad, it was getting about 4mpg with a 302 in a 4x4. It leaked everywhere it seemed, inside, outside...

How you drive has a big effect on mileage. If you are constantly working the accelerator pump you will use more gas, a steady throttle uses less fuel. Having the timing set for best low end power rather than what the book states can also help. Changing the advance curve can go a long way to improving mileage.

Other things have a big effect on mileage too.

Make sure your brakes arent dragging, repack the front wheel bearings and true the rotors and/or drums, replace the brake hoses so you are sure they arent holding some pressure in the system. Make sure the calipers move freely and the wheel cylinders arent stuck.

Get an alignment from a reputable shop and ask for a print out of before and after. Some shops dont know how to do an alignment on an old car, so they just put it on the rack and tell you its done when they havent touched it.

Check the air pressure in your tires. Go with the recommended pressures on the sidewall, since your car came with bias tires and the placard in the car will be wrong. 32 psi isnt always nominal, air pressure in the tires makes a big difference. If the max is 44 psi, run 40 or 42 psi in them if you dont feel like running at max psi. 32 was a common pressure for bias ply tires and it just seems to have stuck around for the last 3 decades.

Make the car roll easier, increase torque in the rpm range it cruises in, and improve acceleration to allow for a lower throttle angle and mileage will increase.

Starfury

Thumpin, that tire information is absolutely incorrect. The pressure on the sidewall of a tire is the maximum operating pressure. Nowhere on any street tire is there a recommended operating pressure, because that operating pressure changes depending on the vehicle they're used on. The recommended tire pressure is located on the vehicle, not the tire.

Normal driving for what is a relatively extremely light car (compared to something like a Vanagon) requires much less than that pressure. 30-35psi is about right for most street tires on Mustangs, depending on tire size. Running 40-44psi on most street tires is going to burn the tread down right down the middle, reduce traction (cornering, acceleration, and especially braking), and make for a rough ride. Hell, many street tires aren't even rated for any more than 36psi.

1971mach1

The pressure on the sidewall (commonly 35lbs) is the max COLD pressure.
Tire pressure can go up as much as 6+lbs when hot (41lbs) but they are built to take the extra pressure. There is much more danger of tire failure with UNDER inflated tires, due to excessive sidewall heat. Check any tire website, they'll say the same thing.

Starfury

Yes, but that doesn't mean you should be maxing out the pressure, or running any more than 35psi in most tires on a 3200lb car. Your tires will be bouncing all over the place instead of flexing sidewalls, and you'll suffer poor traction and tire wear, as I mentioned.

4reboy

+1 to what starfury says, when I first got my car the PO had like 45-50 tire pressure (cold) in all the tires, I quickly lowered that to about 33 when I checked it. My rear tires were missing ALL the tread in the center, there was about a 3" width of flatness in the center. Luckily the front ones were still fine, but I had to buy some used rear tires with 70% tread on them because the flat ones were just unsafe... any more than 30% braking pressure and I was sliding down the road...