Poor Gas Mileage on 200 ci

[Squirrelly]

I just bought in December a 1967 Straight Six Coupe. I bought new plugs, points, condenser, plug wires, Pony Carburetor (adjusted the timing to pull 20 inches of vacuum just like John said) and I still get 12 miles to the gallon.

I call her Jenny (real person but not my wife) because Jenny is one of those women that you don't know which side of the bed she will wake up on. Some days she's out to please her man, the next, I don't recognize her. Actually sometimes, it's might be from one start of the engine to the next. She seems to run great but performance isn't consistent and mileage is crappy. There can be times at idle that she shudders a bit.

I ordered a new Pertronix and Flame Thrower coil in hopes that I eliminate any ignition issues.

Any thoughts on the mileage?

 

[rocklord]

Welcome to the forum.

Automatic or standard?
Your mileage will be dependent on the "nut" attached to the gas pedal Just adjust the "nut" to be lighter on the pedal.

12mpg is less than it should, whether auto or stick. Someone else will chime in with something you can actually check.

Good Luck.

My girl for the last thirty years has been Christine (64 Corvair). She was named after the Stephen King novel/movie for about the same reason- She does what she wants, when she wants, and sometimes it can be scarey. My wife of twenty-eight years still shakes her head at our relationship. I keep Christine away from my 65 Mustang because she would be jealous and do bad things to it since I've been spending more time with it than her.

 

[Frankenstang]

Yeah, wecome aboard squirrelly. The first thing I'd do is verify your calculation method...I assume you are using the odometer? is it accurate? (tire/axle/transmission changes)

Then I'd first check to make sure the choke is completely unloading, especially after reaching operating temps.
Next I'd verify the timing, apart from pulling 20hg I'd make sure you know what your static time is at, as well as make sure the advance is operating correctly.
Compression test might be the next thing to check...although I wouldn't think you could pull near 20hg at curb idle if it was real bad.
An incorrect float setting (too high) could also contribute, but should not be the case with a new carb.

As a side note, my pony carb had a float issue initially (stumble on sharp turns, and eventually stuck open so bad it couldn't be kept running)...they stated, after they fixed it, that they had some troubles with tabs on the floats hanging up. An old shade tree fix for this might have been to rap the side of the carb with the handle of a screwdriver...but couldn't/wouldn't bring myself to do that to a $400 newly acquired piece of equipement.

Oh, and btw...mine is called 'Robin', which I did not choose. It's literally written in body sealant on a panel in the trunk...never wrecked back there, so
I personally would have picked something less androgynous, don't know whether to expect a daughter of the 60-70's, or a someone sporting a high&tight and birkenstocks...maybe a BeeGee :roll:

 

[rbohm]

8) there are many things that affect fuel economy, the biggest being driving style. if you have an excessively rich fuel mixture due to the choke being on all the time, high float levels, high fuel pressure, these can all affect fuel economy. if the engine is not making the power it should due to lower compression, carbon caked valves, a partially plugged exhaust system, can also affect economy.after that you get into too low a rear end gear, short tires, low tire pressure, poor front end alignment, engine running too cold, can all also affect fuel economy.

start with the fuel system, and make sure you have a proper fuel mixture, the choke is operating properly, etc. then make sure the ignition system is in top condition.

make sure the rest of the engine is is good operating condition. if not then until you rebuild it, you wont maximize fuel economy.

if you have the ford o matic 2 spd trans, think about swapping to a C4 3 spd trans, that extra gear really does help fuel economy. if you have a 3.50 or lower rear end ratio, think about swapping to something more like a 3.20 rear end gear, this will lower your engine rpms at speed and reduce your fuel consumption.

make sure you have the proper front suspension alignment, otherwise the car is pushing the tires at weird angles causing excessive friction. same with making sure that you have proper inflation pressure in your tires.

i also agree with making sure that your speedometer and odometer is accurate.

 

[Squirrelly]

Thanks for the posts. It's an automatic C4. I will work on some of the suggestions posted and let you know how it goes.