Improving MPG

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73DusterDriver

73DusterDriver

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Lehi, ut
Ive got a 1973 plymouth duster /6 3.7 it drinks gas like no tomorrow. Ive already replaced all the plug and wires. New choke pull off, and the carb is tuned as good as its gonna get. Is there anything else i can to do improve my MPG?
Thanks
 
Let's start with "what do you have now?"

What do you have and what are you starting with? Just how bad IS the mileage. And how pray tell are you figuring the mileage? ( I used to know a guy who said "I used a half a tank." He meant HE LOOKED AT THE GAUGE)

Have you run a compression / leakdown? That is what shape is the engine in? What kind of miles is on this engine? Use oil? Does it run up to proper operating temp?

How about tune?

Have you checked the "usual suspects" as in does the mechanical / vacuum advance work properly, and while were are there, where is the timing set?

Are you sure the choke is opening quickly and all the way?

Have you done a cursory check to see the carb is not "dropping fuel" into the engine?
 
Yea!!! That too!!!! Or neighborhood hoodlums with a siphon hose!!!!
 
4spdragtop said:
LOL, sad but could be true!
Click to expand...

Reasons why I have a locking gas cap...

Whats your tire pressure?
Are any brake dragging?
Hows those wheel bearings up front? Plenty o' grease? Not too tight?
Adjust the valve lash .010" intake .020" exhaust.
Hows the air filter?
Is the transmission in good working order?
Is the differential lube topped off? Any noises back there?
What car is it? Is the engine stock?
Does your gas have any ethanol in it?

EDIT: also, what plugs are you running? Is it a reman carb? What temperature thermostat are you running?
 
Drive line wear and front end alignment
And all above .. I have seen the heat riser on the /6 exhaust manifold be froze/stuck half closed and that would bring gas mileage down aan easy 5 miles per gallon. . Tune and air/fluid dynamics ..and like I said already all above.
 
/6 Matt said:
Reasons why I have a locking gas cap...

Whats your tire pressure?
Are any brake dragging?
Hows those wheel bearings up front? Plenty o' grease? Not too tight?
Adjust the valve lash .010" intake .020" exhaust.
Hows the air filter?
Is the transmission in good working order?
Is the differential lube topped off? Any noises back there?
What car is it? Is the engine stock?
Does your gas have any ethanol in it?
Click to expand...
Good job Matt.....I am on my phone and type even slower on it
 
Yup All of the above and we STILL don't know what we are "starting with" LOL
 
if its the original carb or just old check the throttle shaft for excessive play = massive vacuum leak. i thought i had my slant running as good as it could but there was a huge vacuum leak that gave me less then 12 mpg highway and maybe 4 around town.
 
/6 Matt said:
Thanks Mike, good point on the heat riser, I didn't even think of that one.
Click to expand...
Yep Matt :glasses7: taking the potatoe out of the exhaust sure makes a difference
I watched a freind drive on a parking lot at work one early morning
and his catalytic converter was glowing red, I told him and he said his mpg has went WAY down (driving 60 miles to work each day) he
replaced it and grained 10 mpg he said. It was a 84 Monty Carlo.
 
memike said:
Yep Matt :glasses7: taking the potatoe out of the exhaust sure makes a difference
I watched a freind drive on a parking lot at work one early morning
and his catalytic converter was glowing red, I told him and he said his mpg has went WAY down (driving 60 miles to work each day) he
replaced it and grained 10 mpg he said. It was a 84 Monty Carlo.
Click to expand...
GM pellet converters and a Rochester 750. A pyromaniacs match made in heaven lol!:banghead:
 
All good suggestions. I was going to respond, but saw the OP hasn't returned to answer any questions. Another fly-by? :angel7:
 
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