Better Mileage?

[73Charger]

I know its like a sin to talk about it with a Muscle Car - but - its got to be asked...

What can I do - cheaply ofcourse - to get better fuel mileage?

My Charger is already pretty good on gas - low octane is fine with low compression 318.

I was thinking that my carb could be tuned to get better mileage when needed without hurting anything but I'm not a guru at tuning a carb.

I know there are two similar models (1405/1406) from edlebrock and I have the one (1405) with what I believe has bigger jets?

I was guessing I could swap with the parts from the 1406 to sip a little less.  Is this a hard thing to do?  or any other parts better?

What about other tuning ideas?  I have adjusted timing by moving the distributer before, and have heard about adjusting some timing on the vac canistor going into it but haven't played with that before.  Would that help?
I'll be replacing my headers since mine have a hole in them - that may help a bit too. I'm thinking about the summit headers.
I don't want to touch the internals on this engine since it has very few miles on it.
I may also put a new air filter on as well.  I've put on a taller one to give it more surface area as well to breath easier too.

[69chargeryeehaa]

i don't think you wanna play with the carb, if you put smaller jets in it your just changing the mixture and could end up running lean which = bye, bye motor over time.  a 318 stock should get good mialage, u should see the 440 im my charger, now that drinks gas like it's going out of style!!!!

it would be a good idea to setup your vacuum advance properly or at least check it out, here's a good guide to do that:  http://www.sweptline.com/tech/engine2.html

how good your fuel economy is mainly depends on you well you maintain your car, check tire pressure often, keep it tuned up properlly, check/clean/replace your plugs often, a good idea would also be to learn how to read your plugs, make sure your running at a good mixture under all conditions. change your oil religously, ect......  here's a good site to learn about reading spark plugs:  http://www.dragstuff.com/techarticles/how-to-read-plugs.html

good luck

[Ghoste]

Hook up a vacuum guage and drive with it for a while.  If you try and drive so that you obtain the highest vacuum readings as often as possible, it will tell you a lot about your driving style and how much it affects your mileage.  Not as fun as jumping in and mashing the pedal though.

[73Charger]

Interesting - I never thought about vaccum before. Wouldn't it be equal to RPMs? iow - the more rpms, the more vac? 
I've learned to drive by my tach with my cars when I am trying to save fuel. how would vac differ?  and I take it you are making a point about the vac canister timing advance affecting mileage due to vac? 

So - another question - does increased ignition timing cause better or worse gas consumption? or is this another trick question?

[Ghoste]

Vacuum is affected by rpm but for this purpose its a function of load.
As to your trick question, more timing can improve mileage up to the point where detonation occurs and then it falls with performance.  Performance and mileage are more closely related than many people think.  They are both improved by an effiecient running engine.  It's how you utilize that efficiency I suppose.
The trick is to use the least amount of fuel but also to use the most enrgy availble in the fuel you have asked for.  Burning everything in the cylinder is better than only burning half and proper timing as you know, affects that.

[Mike DC]

     
You probably don't run a overdrive tranny, do you?

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Then bolt a really tall-ass set of wheels & tires onto the rear end of the car for everyday commuting. 

Hard to beat the bang-for-the-buck of this one.

     

[73Charger]

Good Idea on the wheels & tires.  I have what I assume was the stock pegleg rear with 2.7x series gears,
and with a standard 3 speed automatic I suppose that would help on the highway.
I try to keep the speed down on the highway so my rpms aren't too high.
How big a tire & wheel can one stick on these chargers (in the rear only) without changing spacing/ or body/frame?
Second question would then be - how do you go about adjusting the speedometer for the change in size?

[Ghoste]

Dependign on what diameter tire you decide to go with, there are a series of speedo gears available fro Chrysler all color coded and with differing numbers of teeth.  Just unbolt the hold down clamp on the side of the transmission where the speedo cable goes into it.  Pull the assembly out and swap the gears and put 'er back.  You're done.

[69chargeryeehaa]

well on my 69 charger i have a 8 3/4 suregrip, 3.23 gears, and front tires: 225 60r 15/8"rim/26"tall tire, and rear tires: 275 60r 15/10"rim/28" tall tire, all are BFG's radial T/A's, and have no clearance issues/rubbing.  i put in my combo into a calculator (can't remember where it was) but my final ratio turned out to be 3.08 with just the 28" tall rear tire, so it makes a big difference, essientally reducing your final ratio by running a taller tire alone.   

[Mike DC]

   
You've got a 2.76 rear in there?

Whoa.  The taller tire mod might not help as much as I thought.  I was expecting more like a 3.23 or a 3.55 rearend.

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The taller tires will probably still help some, but there's a limit on how high you can really gear the car before the converter just starts slipping at cruising speed.  For example, there's no point in trying to get a 1200-rpm cruising speed in a car with a non-lockup automatic tranny.

     

[73Charger]

Hmmm I'm bummed now that I got rid of my original lockup converter when  I had the tranny overhauled. I bet IT would have saved gas.  Does that act like a fourth gear?  I'm guessing on the gear ratio. I think its stock still. When I run the 1/4 mile, I can do it in 2 gears so I know it must be 2.xx.  The car I race normally has 3.73s and 16" rims and pulls all 3 gears pretty high. I think my wheels on the charger are stock size 14" or 15"? So I could move up to a 16" without a problem?  I certainly don't want to hurt the tranny to save a couple bucks.

[Chryco Psycho]

advbancing the timing will help & possibly a smaller tire could help

[73Charger]

A smaller tire? now I'm rally confused. I was just wondering how big (tall) a tire I could mount on my stock sized 14" rims.
I was agreeing with the concept that a larger tire would mean less rpms on the highway and less fuel consumed.
It would be nice to have a concept of how much fuel savings that would mean since it would cost atleast $200 for new tires,
and if I had to spring for new rims, that another $200  Right now I have basically no budget so I  was looking first for ways to tune the car more efficiently that may cost little or nothing but my time. 
I know you are the great guru, Chryco so fill me in on how a smaller tire saves fuel. 

[Chryco Psycho]

2 ways , if the converter i sbelow lock up rpm it is slipping so more RPM may lock the converter reducing slippage & wasted power
also if the gear ratio is 2.76 the 318 may not make enough torque & will be lugging to pull the weight of your car again rasing the rpm slightly may help the 318 work more efficiently

[73Charger]

Thanks for the explanation.     Since I replaced my lock up converter with a non lockup - I guess the first problem is not a problem, so it would only be a problem if my car was "lugging along" I guess, which has certainly never seemed to be a problem with my little tires.
  Theres not a whole lot of get up and go to it.  It only runs a 16.88 at 84mph quarter, (I only shift it once) I don't use it for racing, but only as a pretty much everyday driver in the summer since it seems to use less gas than my Formula which we do race.

I do have different sized tires on the the front and back - just cause that's how I got it 5 years ago but they are all on 14" outlaw II wheels which I think are the same size.  One set is a bit wider but I think lower profile, and the other is wider but lower profile. 

I was thinking maybe I could get a bigger profile tire and keep the same rims as long as my car wasn't lugging along as you put it. 

I'm not sure what the rear gears are on it, but my guess is they are original - so whatever came on a 73 SE with 318 and no AC

The car pulls pretty good on the low-mid range for everyday driving but it always feels slow to me.  It has a good "snappy" feel when the throttle moves the first 1/5" or so but that it goes into its normal "slow feeling"  - It does the same thing under full throttle. For a while I was wondering if it was ever making it to full throttle - especially when seeing how slow it was on the track, but later on I've heard others on this great forum admit that theirs were as slow as this too.  I know bigger tires would make this even worse, but I'm not racing anybody with it. - really - I'm not!  I just love driving something that makes so many heads turn - even if she IS still in primer.