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  #1  
Old 04-12-2004, 07:23 PM
CaseDawg CaseDawg is offline
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Default i want a 318 with good gas mileage...possible?

hi all, this is my fist post on this site. i have a 1970 dart swinger that has a /6 in it and i want to put a 318 in it. what can i do to get good performace out of it and still have good gas mileage? i've heard that i could get anywhere from 13-25 so i don't know what to think. i got a 318 for free from my friend and i'm debating still whether or not it's worth it to swap the 318 in for the slant 6. the slant just doesn't seem to cut it and the performance parts are pretty expensive. what kind of gas mileage could i expect from a 2 or 4bbl slant with headers and new exhaust? thanks for your help.


casey
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  #2  
Old 04-13-2004, 12:07 AM
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rumblefish360 rumblefish360 is offline
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This is a slice of cake. However, there are give and takes to the performance end. How fast you want to go and what kind of mileage you can live with. It's a catch 22. You can do preety well without bad gas mileage.
My question(s) to you is;
How much mileage are you looking to get?
How fast do you want to go?
If it's just basic pep, your in good shape.
I yanked 20 mpg's out of my '79 Dodge Magnum with a 360 4bbl.
My mech nail 25 out of his 318 in a car like yours. So yes, it's possible.
IMO, take that slant six and ride yourself of it.
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  #3  
Old 04-13-2004, 12:07 PM
CaseDawg CaseDawg is offline
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i would like to get in the low 20's. overall top speed is not what i'm looking for. i just want to be able to get some good acceleration, maybe burn some tires, but i doubt it. what could i do to it to make it perform but with good mileage? i was thinking of an eldebrock intake and cam package for idle to 5500rpm power, a set of headers(i don't know what tube size and all that yet), a 4bbl carb(probably a remanufactured eldebrock to save some cash), dual exhaust(what would you recommend?), and probably just a 2.76 rear end cause that is all thats available to me. what do you think? any suggestions? i really don't know what i'm doing so any help would be great. thanks.


casey
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  #4  
Old 04-13-2004, 01:33 PM
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MoparMarcIdaho MoparMarcIdaho is offline
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Arrow fuel economy

With the price going up up and away,I get this question more and more.Go ahead and put a 4 barrel intake on but consider for street use a 2 barrel on an adapter plate.Once its all set up you can change it over in about 15 minutes.Its been my experience that something off a GM (sorry guys) will do better on gas.Small baseplate off a 283-307.Lots of tricks to make the other stuff do better but this works too.
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  #5  
Old 04-13-2004, 05:35 PM
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rumblefish360 rumblefish360 is offline
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My all stock 360 2bbl got a whooppping 10 mpg's on the Hwy. So I fussed around. The 4bbl 625 Carter did a better job in the power and mileage dept. hands down. Never do a 2 bbl. Never never never. There flow ratings are different to start with. So you can be fooled easy.

CaseDawg;

That rear ratio is ideal for mileage on the hwy. Hold on to that.
For the moment, skip the cam.
Open aircleaner is best.
600 cfm carb max. Holley, Carter, whatever. (I like the AVS or T-Q)
A dual plane. The Edel. Performer for a 318. (Thumbs up!)
Headers. Hooker makes them preety well. Search threads for opions and fitting problems. The with "A" bodys is room. TTI makes the best headers, but, at a whooping price.
2-1/4 inch exhaust with a nice turbo muffler. A "H" pipe would be good to use in the system.
Upgrade the ignition box. Go MoPars Chrome at a min. An MSD would be better/best.
Mopars Viscous fan or an electric fan.
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  #6  
Old 04-13-2004, 06:12 PM
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rumblefish360 rumblefish360 is offline
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Why O why must I have only 2 min.s to make an edit?????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ?????????????????????????????????????????????????? ????????????????????????????

1 freakin mistake on the mouse and your screwed!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!

MoparMarcIdaho;

The adapter plate for a 2bbl. use is more of a headache to do then just useing the foot wisely. The primarys on a Carter/Holley 4bbl of 600 cfm are slighty under 300 cfm at a greater pressure drop than a 2bbl carb with a lesser presure drop.
Use of another 2bbl. carb on a 4bbl intake now requires ethier some fab work or a purchase of an adapter plate. Then you have to make the linkage work on off angles.
Why bother??????
Then to reuse the stock aircleaner???? Or an adapter ring for a 5-1/4 neck aircleaner?

I scored a cheap J-yard intake, boiled, blasted and painted for $55. Gaskets, intake, carb and valve covers, $35.
New, out of the box Carter 625 for something like $235. (???) (I forget, it's been awhile)
You could go the route of a Cheap open aircleaner for about $25.
Total, $350.00 done right. 20 mpg's from a '79 Dodge Magnum. Full tank, reggie weight of 3750. Never mind the stero, full tank of gas and me.

(Never got to headers thogh, damn I did wanna try that.
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  #7  
Old 04-13-2004, 06:35 PM
CaseDawg CaseDawg is offline
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ok, so i need to hold off on the cam. do i really even need the cam? am i going to get some good acceleration and power from the intake and exhaust upgrades? also, i found an engine rebuild package that includes a 4bbl cam for $40 more onto the overall price. do you think that is just a stock carb? would that be any good? thanks.


casey
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  #8  
Old 04-13-2004, 07:11 PM
hotrod7043 hotrod7043 is offline
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Ihad a 76 aspen rt bone stoxk with a 318 2bbl ir got15 mpg and ran 17.70 atsears point. we put a 3.21 81/4 and dual exhaust Tq 340 intake with a 73 400 Tq it ran 15.20s and got 21 mpg.
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  #9  
Old 04-13-2004, 09:01 PM
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MoparMarcIdaho MoparMarcIdaho is offline
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Arrow OK then

2 barrel with adapter plate bad ju ju.On an 84 gmc short step 4x4 I had,I replaced the edelbarf performer on an adapter plate for a rochester 2 barrel off a 262 olds v8.Looked like a Qjet and took the same kit,but back of the thing was closed off, no throttle plates of anything, and brought it from 5 mpg to 17 with a 4sp.Just lucky I guess.
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  #10  
Old 04-13-2004, 09:38 PM
aDjUSTER aDjUSTER is offline
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Case Dawg

Just going to the 318 from the 6 is going to be a power boost which should run 19's easily. Don't know what your looking for as the other posts have given you some good advice for a beefier set up than a stock 318. You mention that your looking for 20's and good gas mileage. A stock 318 will fit the bill. It will give you more performance than the 6 and will give you good mileage.

If your looking for something that will give you a seat of the pants feel with a 2:76 gear then you will have to step up the ladder a bit. Then a dual plane stock 340 manifold and carb with 1-5/8" headers and dual exhaust will take you to the next level of perfomance without sacrificing too much in the way of mileage. Again this is dependent on the way your foot reacts with the gas pedal because of the extra power. If you abuse it you will lose it.

If you want to impress the crowd with burn outs and want to run 14's then your next step is a cam with a better gear and convertor, if automatic. Possibly time to pocket port the heads and think of more compression and suspension upgrades. This route will probalbly still give decent mileage if not abused. But what is decent to you? If your looking at impressing everyone with your burn outs and are looking at your time slips in awe con't expect to get 25 to 30 gpm.

Speed is relative to the amount of fuel utilized to get there. The more you step on it the less the fuel mileage. You can get some decent mileage out of a high horsepower car if you limit the pressure on the old gas pedal. It all up to you with what you want. If your looking for some one to tell you that with this and that you can go around town full throttle, all day long, beating every other car you see and get 30 mpg then you better do a re think. All of the suggestions given before this have been good suggestions to take you to several different levels from bare stock to a good performer, but, there is no one going to tell you that you can get 30 mpg because it depends on your foot and only your foot.

Rumblefish gave you a good performer package and stated that he got some decent mileage with his package. This doesn't mean that you will get the same because you may not drive the same way as he did to achieve his results.

Every package given will give you a better performance than the 6 and will give you some decent mileage if the gas pedal is treated with respect. Now you will have to make a decision on how much power you want. Your pocket book will tell you how much you can get at this point. You can always go up from there. Hope that your decision will bring a smile to your face and you will always have the option of slowly sneaking up on better and better performance. You have a lot of options going for you with starting with the stock 318.
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  #11  
Old 04-13-2004, 10:18 PM
GaryS GaryS is offline
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Gas mileage in the 20's is a snap with any 318. My stock '68 Fury III got 22 on trips. My '85 Fifth Ave got as high as 25, but didn't have near the performance of the Fury.

One thing to remember, if you dump the slant, you will also have to swap the transmission and driveshaft. If you have a 7-1/4" rear end, it won't take many burn-outs before you are looking for an 8-1/4 or 8-3/4. Those rear ends for A bodies are getting rare and expensive. Also don't forget a new radiator, exhaust system and a bunch of miscellaneous junk. If you have 13" tires and wheels, you will need to get 14" rims and bigger tires.

Oops!...almost forgot. If you have 9" brakes, they won't begin to stop that car.

I would suggest that if you want a V8 powered car, that you trade yours off. Unless the body is super cherry, you will spend far more swapping engines than swapping cars.

Also don't sell the slant short when it comes to performance. A Super Six setup with duals and electronic iginition will put you in about the same performance and mileage range as a stock 318 and for a lot less money than a swap. I've seen several street driven slants that easily run 15's and that's not shabby.
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  #12  
Old 04-13-2004, 10:54 PM
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rumblefish360 rumblefish360 is offline
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aDjUSTER
Quote:
Rumblefish gave you a good performer package and stated that he got some decent mileage with his package. This doesn't mean that you will get the same because you may not drive the same way as he did to achieve his results.
Thank you, the secret to the mileage is a light foot on the thottle and a lean jetting on the carb. Steady, constant speed on the Hwy. was how I deterimed max mileage. Drove the car till near empty and filled up. Did the math. best I ever got was 22 mpg. But that was not constant every week. Overall, it was 20 mpg for the norm. It would dip to 17 if I was a little heavy on the pedal, out who-harring.

CaseDawg;
Quote:
am i going to get some good acceleration and power from the intake and exhaust upgrades?
Yes! This is the basic bolt on horse power mods. They do not really tax the engine. There just letting the power free instead of being corked up.
Lay of the cam for now. If you want to try it out later, do it. Just save the old cam. Oil it down and wrap it up in plastic wrap. Like your Mom used for storeing food in the fridge.
This way, if the new cam is not the "IT" you were looking for, it's just a afternoon to swing it back in.
Otherwise, doing a cam swap, the right way, will included the extra price of timing chane, springs and possible liffters in addition. This can add up fast. Lets do the K.I.S.S method first. (Keep It Simple Silly) It'll also save you money.
Quote:
do you think that is just a stock carb?
In the rebuild kit?
The stock 4bbl carb that came on a 318 is the small T-Q. The only other carb I would use is an AVS. But thats me. You'll only need 600 cfm for this engine. MAX. Holley, Demon, Edel, OE Carter AFB, AVS, or T-Q or a Rochester. Whats your flavor?
Will it be good you ask? Ans. Yes. It'll be fine. Not to worry.
Read GaryS post on possible parts needed. The slant6 tranny will not bolt up. New driveshaft needed. Rear end is fragile if you start upping the power anti. Don't beat on the car with that rear. (Boooom!) An 8-1/4 will do. Plenty of them around.

MoparMarcIdaho; Now I see where you got some of that mileage. 262 carb ='s a lean runner and smaller carb probably. That 262 made in the 80's? (Mom had one in a Cutlass.)
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