318 engine, MPG and what makes it better

[WP29440SE]

yep , I'm going to be that guy

if you are going to worry about 3-4 miles per gallon in a 40 year old car that's running a four barrel , park the damn thing and drive a Camry, or get a better job so you can buy gas and not have to worry about mileage.

 

[Kern Dog]

In the OP's defense, it can be a bit of a surprise if you are used to driving a newer car.
In my view, 40 years of product development HAS to have some effect on fuel economy, right? A 1970 VW Beetle had a small air cooled pancake 4 cylinder mill. The car weighed less than 2000 lbs but the car only got mid 30s mpg ? A 2018 Challenger with a V6 weighs double that, is far more comfortable, quieter, safer and gets about the same freeway mileage.

The 74 B body was a decent car. A car that was built as a 318 model with a 2 barrel carburetor, a 904 transmission, a 8 1/4" axle with a 2.71 or 3.21 ratio and narrow tires could get near 20 mpg on flat ground if driven right. Once you start making changes from that to heavier parts and wider tires, the mpgs start to drop off.

 

[levicah]

yep , I'm going to be that guy

if you are going to worry about 3-4 miles per gallon in a 40 year old car that's running a four barrel , park the damn thing and drive a Camry, or get a better job so you can buy gas and not have to worry about mileage.

Be that guy all you want...but learn to read. I wanted to know if this was to be expected. Aint worried about anything. Or you could post something useful...I'm that guy too.

 

[mopar 3 B]

You might have someone evaluate what you have that knows what he is looking at. Right now it just a guess with no verification of what you have been told.

 

[levicah]

You might have someone evaluate what you have that knows what he is looking at. Right now it just a guess with no verification of what you have been told.

your concerns are legit, but the only thing I dont know first hand is the rear end and whether he swapped the cam out. The trans, the headers, the performer intake, the 4 barrel, the traction bars have all been added. Verified by me. I'd like to think he did some work on the heads, but he never claimed that he did. I dont know why he would upgrade the rear end on a 318, but given everything else he did do, I doubt he would lie about that. No guessing, I just tried to ask if this all added up to 11 mpg. or could I do better. Thats it.

 

[mopar 3 B]

your concerns are legit, but the only thing I dont know first hand is the rear end and whether he swapped the cam out. The trans, the headers, the performer intake, the 4 barrel, the traction bars have all been added. Verified by me. I'd like to think he did some work on the heads, but he never claimed that he did. I dont know why he would upgrade the rear end on a 318, but given everything else he did do, I doubt he would lie about that. No guessing, I just tried to ask if this all added up to 11 mpg. or could I do better. Thats it.

With out facts a ligit guess your mpg sucks.

 

[JB400]

How about a pic of the rear end? I have my doubts that it is a dana whereas I bet it's probably 8 3/4.

How wide of tires are you running?

 

[mopar 3 B]

8 3/4 has a solid non removeable rear cover. Tire width has little to do with gas mileage

 

[rumblefish360]

However it IS the little things that add up.

Tire size please.

FWIW
I also forgot to mention “A little thing” in my last post and that would be spark plug gap can be increased greatly with the msd. I ran mine @ .050 with excellent results.

 

[rumblefish360]

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

Thanks. I just wanna we to be clear that we both knew that.

yep , I'm going to be that guy

if you are going to worry about 3-4 miles per gallon in a 40 year old car that's running a four barrel , park the damn thing and drive a Camry, or get a better job so you can buy gas and not have to worry about mileage.

Wow! EZ there Francis! How is trying to maximize what you have a sin and a sign of your little degrading speech? A 3-4 mpg loss in a basically stock 318 is a huge loss. Never mind what he is getting.

When I first picked up my ‘79 Magnum with the 360/2bbl., after a tune up I was rewarded with a whopping 10 mpg! According to you, this is not a problem! I should expect this and accept this as OK? SCREW THAT!

The first thing to go was a trio of parts. The barley functioning lean burn, the leaking 2bbl. & intake. The MP orange box replaced the lean burn, a year correct iron 4bbl. Intake was used and the carb was a Fed/Mougal 600 AFB. While mileage increased, I never got to recording the gain due to the deep need for an exhaust system. The stock decrepit exhaust was dropped into the recycle cam for a exhaust manifold dual 2-1/4 set up with an H pipe and a then new law mandated twin cat set up. 17-18 mpg’s was happening. Before I finished tuning the carb I decided to get a msd6. That brought me to 20 mpg’s at the maximum return.

FWIW, the distributor was an older vacuum advance from a truck and the air cleaner was a OE trap door with paper filter.

This was a darn good daily driver making 40 mile round trips commuting in and out of the city. It also made many many trips from the Island to Virginia and Georgia. Something I wouldn’t want to do at 10 mpg but at 20, well, that is much better in my book any dang day.

 

[YY1]

Good mileage also means the engine is running efficiently.

That's a big plus for performance as well.

 

[Don Frelier]

Good mileage also means the engine is running efficiently.

That's a big plus for performance as well.

Let's not forget longevity, when they run right they last.

 

[Dibbons]

Driving as if there were an egg between foot and accelerator does not always make a difference. Tried that driving my parent's new '71 383 auto Road Runner (3.23 rear end) and it was exactly the same as my "normal" driving @ 12.5 MPG (daily 50 mile round trips to High School and back). The main problem I had in the past with a 318 and poor mileage was a non-functioning distributor vacuum advance, but probably not the fault in this case.

 

[oldbee]

ALL good points, you need to recheck everything to see where you stand. Then, get a little creative with what you do. Smaller primary throttle bores on carb; better ignition,etc. It’s all possible.

 

[Kern Dog]

8 3/4 has a solid non removeable rear cover. Tire width has little to do with gas mileage

THis is wrong. A wider tire has a larger contact patch. The extra traction also means more drag.

 

[rumblefish360]

THis is wrong. A wider tire has a larger contact patch. The extra traction also means more drag.

True, but not drag. “Rolling resistance.”
(Or was that more drag racing? LOL!)
A wide tire serves well for traction off the line or carving corners. After that, your basically just pushing the tire along down the road. This is HP loss requiring more torque which requires more fuel to maintain the same speed.
Now we have less mileage.

 

[WP29440SE]

Be that guy all you want...but learn to read. I wanted to know if this was to be expected. Aint worried about anything. Or you could post something useful...I'm that guy too.

I've had 4 barrel carbs that get 15 mpg , I've had carbs that get 8 .

 

[rumblefish360]

Wooooooo-Weeeeeee!!!!

There’s a (8) barrels of fun!!!!!

 

[Cranky]

Was running a TR on a stock stroke 440 running high 10's with two 750's and it was getting 1 mile per 4 gallons....but it was wide open for that

 

[mopar 3 B]

I can remember 4 mpg but gas was $0.35 per gal. . Cost a whole $5 to fill the tank.