318 engine, MPG and what makes it better

[levicah]

Everyone is telling me I should get around 16 - 17 mpg. Right now, I'm getting 10 - 11 mpg.
I'm just wondering where I should be looking to increase the mpg.

The plugs look slightly rich, black but dry. The car idles very smoothly and accelerates smoothly. If I was turning the distributor by hand...I couldnt hope for a smoother consistent sounding engine.

In town or around 25 - 35 mph the car "feels" like it wants to go. Cant really explain it, it just seems a little congested maybe. It's much "happier" or responsive at 40+mph.

Sometimes I'll get that raspy rattling sound if I but my foot down...is that "pinging"?

So, given the facts listed below, should I be expecting better gas mileage?
and what should I be looking at first? Thanks once again!


74' satellite, 318 with edelbrock performer intake, edelbrock 1406 600 cfm 4 Bbl carb with the mesh triangle air filter, dual glass packs and headers. 727 torqueflite auto trans. Distributor looks 2nd gen (no points) but doesnt look like performance. I dont know if the cam was changed, engine runs very smooth.

 

[747mopar]

First I'd ditch that filter, not that it will help with performance but they catch fire and melt if you ever experience a backfire. What gear ratio are you running? From the sounds of it you could use some carb tuning to fix those black plugs. Yes the rattling sound could be pinging, what's the compression ratio and what octane are you running? Might try some higher octane to see if the rattling goes away, if not you might try playing with the timing to help it out. I'm not that familiar with the Eddy carbs but I'm sure someone who is will chime in.

 

[65-440]

Is your current MPG readings around town or Hwy? My 68 coronet .030 over 383 is getting consistent 18mpg on the Hwy but closer to 10 around town ....

 

[WileERobby]

I suspect carbon buildup, and you're running rich.Do not continue to run with the pinging.

 

[YY1]

For reference my 73 2 barrel with only dual 2 1/4 exhaust as a mod is getting 14 in mixed driving.

I think it should do just a bit better.

Fixing your rich condition may bring it up a couple.

 

[JB400]

Check your tire pressure and switch to a lower viscosity lubricants. You also want a higher gear in the rear end. An overdrive transmission would be a good upgrade as well

 

[Demonic]

I would dig deep into the carb tuning, find the cause of the black plugs. Pinging is really bad - it starts before you can hear it, so if you hear it, it's already gone on for some time. Verify the balancer timing mark, re-curve the distributor for as much initial advance as possible, 10-12* but keep the full advance to 34-36*. Run the vacuum advance - it's designed to help mileage.

 

[mopar 3 B]

Clean the trunk out, reduce the weight.
Black plugs. Fuel or oil maybe both. Check the compression, get some vacuum readings. Maybe consider your driving habits. Lots of factors in MPG

 

[rumblefish360]

Everyone is telling me I should get around 16 - 17 mpg. Right now, I'm getting 10 - 11 mpg.
I'm just wondering where I should be looking to increase the mpg.

The plugs look slightly rich, black but dry. The car idles very smoothly and accelerates smoothly. If I was turning the distributor by hand...I couldnt hope for a smoother consistent sounding engine.

In town or around 25 - 35 mph the car "feels" like it wants to go. Cant really explain it, it just seems a little congested maybe. It's much "happier" or responsive at 40+mph.

Sometimes I'll get that raspy rattling sound if I but my foot down...is that "pinging"?

So, given the facts listed below, should I be expecting better gas mileage?
and what should I be looking at first? Thanks once again!


74' satellite, 318 with edelbrock performer intake, edelbrock 1406 600 cfm 4 Bbl carb with the mesh triangle air filter, dual glass packs and headers. 727 torqueflite auto trans. Distributor looks 2nd gen (no points) but doesnt look like performance. I dont know if the cam was changed, engine runs very smooth.

I get 20 mpg’s out of my 360/4bbl./904/276 geared rear in a loaded Dodge Magnum.
Tune tune tune! No headers, twin cats, 2-1/4 exhaust to the bumper. Edelbrock 600 carb and a MSD6 box.

You also want a higher gear in the rear end. An overdrive transmission would be a good upgrade as well

Higher gear? In what way? Numerically?
An O.D. Trans?
Oh! A t like the U.S. government and just throw buckets of money at what they think is a problem for mediocre results at best?
LMAO!
Come on man!!!!

I would dig deep into the carb tuning, find the cause of the black plugs. Pinging is really bad - it starts before you can hear it, so if you hear it, it's already gone on for some time. Verify the balancer timing mark, re-curve the distributor for as much initial advance as possible, 10-12* but keep the full advance to 34-36*. Run the vacuum advance - it's designed to help mileage.

BINGO! This ^^^^^^ is where you start!

Once you get to tuning your engine with the carb and ignition all ironed out, I then suggest a MSD or other multiple spark striking ignition box for the sole reason of the multiple spark for mileage purposes. ONLY!

That air filter is causing you to run crappy because it is restricting air flow. Dump it, hang it on a wall for facet practice what ever, get rid of it
The air filter to replace it should be better than 10 inches round (popular and inexpensive) and at least 2-1/2 inches above the carb as measure under the lid. A flat base will do that and be best IF it fits under the hood. Avoid a drop base filter if you can.
Any factory 4bbl. Air cleaner should fit the bill.

If your tuning this yourself (highly suggested!) and your a rookie, adding a simple 02 sensor is a super good idea! Stroll through Summit racing for this. It is a huge help in basic tuning for rookie and pro alike. It will speed things up really fast.

What size tire are you running?
What is your gear ratio?
What isn’t stock on the engine?

 

[JB400]

Going with a higher gear means numerically lower. Or so I was taught.

 

[oldbee]

Drive it like there’s an egg between your rt.foot and the throttle pedal. (probably not gonna happen!)

 

[Cranky]

Drive it like there’s an egg between your rt.foot and the throttle pedal. (probably not gonna happen!)

Was going to say the same thing! Some people can't get good mileage from a 4 banger. One time I tried the 'egg' method with my 74 Dodge pickup with 3.55's and 27" tall tires. Well, it surprised me with 21 over all but man, that was not fun at all. Regular in town with some freeway averaged around 16 with a /6 in that dang pick up but at least I kept up with traffic.....

 

[Kern Dog]

There are a few strikes against you here.
The car is no lightweight. My guess is that you are around 3500 lbs. Well, not YOU...the CAR.
The 318 was designed with a small camshaft, weak valve springs, a small 2 barrel carburetor and moderate compression. In stock form, it ran great and lasted a long time giving decent mileage in lighter cars. A 77 Power wagon with a 318 will get only a few mpgs more than a 440 because the 318 has to strain to get up to speed while the 440 gets there easily. The harder the engine has to work, the more fuel it will use.
The 727 is a heavier transmission with larger internal components as compared to a 904. It takes more power to operate a 727.
The Edelbrock 4 barrel will not likely get the same fuel economy as a Thermoquad 4 barrel.
Gearing matters too. Adding the 518 overdrive may help on the freeway but cost you at lower speeds because it is based on the 727, again a heavier transmission with heavier internal parts.

 

[mtbase]

I know that Edelbrock is equipped with the electric choke... but have you checked to see if it is opening up completely? Could explain black plugs and a congested feel

 

[YY1]

check the heat riser valve in the pass side exhaust manifold.

if it's stuck (common) you're choking your exhaust.

Mine was sticky but not fully seized, so I broke it out while I had the manifolds off, and then made sure the shaft and what was left of the butterfly were stuck in the least restrictive position.


for reference on timing- the book calls for 0* on my 73 (and likely 74 as well), and anything more than that causes pinging in my car.

 

[levicah]

There are a few strikes against you here.
The car is no lightweight. My guess is that you are around 3500 lbs. Well, not YOU...the CAR.
The 318 was designed with a small camshaft, weak valve springs, a small 2 barrel carburetor and moderate compression. In stock form, it ran great and lasted a long time giving decent mileage in lighter cars. A 77 Power wagon with a 318 will get only a few mpgs more than a 440 because the 318 has to strain to get up to speed while the 440 gets there easily. The harder the engine has to work, the more fuel it will use.
The 727 is a heavier transmission with larger internal components as compared to a 904. It takes more power to operate a 727.
The Edelbrock 4 barrel will not likely get the same fuel economy as a Thermoquad 4 barrel.
Gearing matters too. Adding the 518 overdrive may help on the freeway but cost you at lower speeds because it is based on the 727, again a heavier transmission with heavier internal parts.

Wow, lots of stuff to take in here, previous owner wrote this down..."9 3/4" rear end, standard gears - probably 273 gears." This is greek to me and I am in fact a rookie. Is this gearing good or bad for my set up? I'll have to google a lot of these suggestions just to get a grasp. Like checking the electric choke. I dont recall seeing a heat riser valve on the headers, I will check. Oil new, fuel clean and new. Using reg. unleaded gas. Yeah for a 318, this car does want to boogy. I bought a flat, round air filter 2'' x 9" diameter. Anything larger in height or diameter and I'm through the hood (no scoops or contouring).

Yeah, I'm not looking to spend, just want to be sure I'm running optimally for what I have. Some friends doubt they left the cam alone...but it does idle and accelerate very smoothly. I probably should admit it was up on blocks for 14 years. I sprayed fuel stabilizer in the carb until it choked out, and there it sat waiting for my son to grow up.

 

[Kern Dog]

I would be really surprised to find a 9 3/4" axle in the car. They were last used in the B body line in 1971, though a man could have installed a 9 3/4" unit years after the car was built. That axle is made by Dana and often called the Dana 60. It is THE heaviest and strongest axle ever used in any American car. It was used in 4 speed cars behind the 426 Hemi and 440. They came in 2 axle ratios, 3.54 and 4.10. That axle would be serious overkill for any 318 car. Just like what I wrote about the 727 being a heavy transmission, the Dana 60 takes more effort to turn due to the heavier components.
the 71-78 B body cars could have been fitted with a 9 1/4" axle. That unit is much lighter and was available with more ratios: 2.71, 3.21, 3.55...maybe more.

 

[levicah]

I would be really surprised to find a 9 3/4" axle in the car. They were last used in the B body line in 1971, though a man could have installed a 9 3/4" unit years after the car was built. That axle is made by Dana and often called the Dana 60. It is THE heaviest and strongest axle ever used in any American car. It was used in 4 speed cars behind the 426 Hemi and 440. They came in 2 axle ratios, 3.54 and 4.10. That axle would be serious overkill for any 318 car. Just like what I wrote about the 727 being a heavy transmission, the Dana 60 takes more effort to turn due to the heavier components.
the 71-78 B body cars could have been fitted with a 9 1/4" axle. That unit is much lighter and was available with more ratios: 2.71, 3.21, 3.55...maybe more.

I dont remember the context, but this all sounds very familiar. I do believe the rear end was upgraded as was the transmission also. The guy had plans for the car but I dont remember what those plans were, or if he even knew what he was doing. Did all these cars come with torsion bars instead of typical front end suspension? Also has traction bars.

 

[Kern Dog]

Mopars do not need traction bars for various reasons. A 318 car absolutely does not need them. It is extra weight for no gain.
The way that the leaf springs are constructed in the Dodge and Plymouth cars is a bit different than in the GM and Ford cars.
Mopar REAR wheel drive cars were built with torsion bars from the mid 50s until 1989.

 

[levicah]

Mopars do not need traction bars for various reasons. A 318 car absolutely does not need them. It is extra weight for no gain.
The way that the leaf springs are constructed in the Dodge and Plymouth cars is a bit different than in the GM and Ford cars.
Mopar REAR wheel drive cars were built with torsion bars from the mid 50s until 1989.

The owner was from australia, I have no idea why he did what he did or what his plan was. Maybe the traction bars are for show...who knows. Also there are no heat risers. Thank you for your input!