302 and 12 MPG...

[aldeswarii]

Ok, so my recently rebuilt 302 is getting horrible gas mileage (about 12 is the best I've had) on 2.70s and a rebuilt C4.

302 .030 over
Edelbrock Performer Intake, Cam, Lifters, 650 CFM Carb ( All from a kit )
Pertronix Flamethrower

I don't get it.

 

[12sec67]

check your timming, plugs & gap, then re-jet your carb!

 

[7D3mach]

Mine is about the same except I usually get 10-11mpg (highway). I'm running 2.73s and a C6. My mods are Edelbrock cam, 351W valves, all new valvetrain, port and polish, .020 over, pertronix ignition, etc. (I know I'm leaving stuff out, check out my website for a whole list.) I don't know what it is either, and yes it is tuned right.

 

[65fastback2+2]

2.73's are probably too low letting the convertor still spin instead of locking, i know d.hearne has suggested this to me before

 

[rbohm]

there are a number of things that affect fuel economy. they are;

1: carb jetting

2: float level

3: fuel pump pressure

4: vacuum leaks

5: ignition timing

6: vacuum advance(or lack there of)

7: gearing

8: driving style

9: carb size

10: state of tune

11: compression ratio(or lack there of)

12: exhaust problems

13: acclerator pump output


etc. take these one at a time and fix any problems first. then work on your driving style.

 

[Hack]

Ok, so my recently rebuilt 302 is getting horrible gas mileage (about 12 is the best I've had) on 2.70s and a rebuilt C4.

302 .030 over
Edelbrock Performer Intake, Cam, Lifters, 650 CFM Carb ( All from a kit )
Pertronix Flamethrower

I don't get it.

How does it run? 12 mpg doesn't actually sound that bad to me if you're driving it hard in the city. Now if that's all gentle highway cruising at 55 mph, 12 is bad.

It's also possible that you have a fuel leak.

I don't really understand why classic car owners get all upset and worry about gas mileage. Just drive it and have fun. If it isn't performing well, sure do some tuning. If you're after great fuel economy, putting aftermarket performance parts on the car is NOT the way to go.

Buy a Yugo or a Chevette. They get better gas mileage.

 

[2nd Mustang]

12 mpg, you're doing darn good. I'm a lot less, single digits.

 

[Old Blue]

i must be doing well. i get 14-16mpg. set up is

69 grande
302 stock
600 cfm edelbrock carb
pertronix II ignition
t-10 4-speed
whatever gears were from the factory for a 69 grande 302 automatic

 

[Edbert]

Have you attached a vacuum gauge with a long hose and looked at it while you drive around town or down the highway?

Driving style can affect mileage more drastically than many folks realize. I got 21.8mpg from my 05-GT last tank but many folks in the 05 forum are seeing 15-16mpg.

 

[Stang_1973]

Does seem a little low for the performer setup. When I had that similair setup I was getting about 15-16 but that was alot of hiway miles. Now with the bigger cam and different heads I am geting around 14.5

Oh and c4 with a 3.00 rear gear.

 

[7D3mach]

Ya, I think my poor mileage is from a heavy right foot. Oh well its worth it.

 

[Jonstantine]

cruising at 75 with 2.80's i got about 16/17 mpg with eddy performer setup

trip from my parents to norman is about 155 miles or so and it took just over half a tank

when the points went bad, the gas mileage did drop alot though

 

[notny41]

That must be why they started to make mustang II's in the seventy's gas crisis times....