360 small block

[1975sport]

So my dads gonna do some work on a toyota and my shop teacher said he would give me a 360 from a 76 aspen with 70,000 to 90,000 miles on it for my 1975 dart sport i have headers off the old 340 and the manifold, i also have a 4 barrel and the motor right now has a 2 barrel carb. I was wondering what mpg i'd get out of a 360 because i wanna use the dart as my daily driver to highschool and back. Right now im driving the 99 chevy with a 5.7 vortec i was wondering if i would get better gas milage than my big gas gusler.

Thanks, Nick

 

[1970 La]

i have got a 1979 1/2 ton dodge full time 4x4 360 2 brl auto transmission that gets 14 mpg with a 3.55 gear. i would think in a dart with a decent gear you should at least get the same. this is driving the speed limit. the chev probably gets around 10 mpg?

 

[1975sport]

yeah my chevy gets around 10 or 11 and in short trips to school and around town it really feeds on my wallet

 

[dodge freak]

its not going to get that much better mpg

i got a 92 olds ceria, has the 3.3 v6 no od trans and gets me low 20's with a heavy foot. car isn't worth $1,000 yet gets me all around town. is it fun to drive, heck no..safe in a crash, i doubt it..cheap to run, yep

 

[rumblefish360]

Lets see. a 360 of the low compresion kind in a Dodge Dart Sport.

What gears and tires.

I can see 18 - 19 MPG Hwy. with 2.76/2.79 gears

 

[dodge freak]

18--19 would be tops and that be at a steady speed, not city driving.

I had a 318 in a heavy 77 Gran Fury with high gears, 2.73's..it was mostly stock expect for dual exhaust-no cats and no egr-I went in to the intake and cap those port holes even to help flow. It could hang with the new 84 mustangs at the time but got beat flat out in the 1/4 mile.

One summer I got kicked out and was trying to get by on little cash as possible. Used to do 55--60 tops on the freeway and babied it around town, it got 16 mpg and I was being pass by everybody on the road--no fun

my 170,000 mile Olds I zip around town-compare to that Fury and it gets right around 22 mpg last time I checked

 

[OwdKasd]

Where's the old 340? :-D

 

[dodge freak]

The old 340 gets me a firm 11 mpg which I'm pleased with but can't use it everyday in part to the poor mpg....but then if it had 2.73's vs 3.91's it would not be the same car

 

[OwdKasd]

The old 340 gets me a firm 11 mpg which I'm pleased with but can't use it everyday in part to the poor mpg....but then if it had 2.73's vs 3.91's it would not be the same car

Yes change the gears or take other measures to boost the MPG (JMO). By the time you add up the expense of changing out the engine plus the work involved, what did you really save. For example. You sell a 30 MPG VW and replace it with a 40 MPG Prius. The extra expense is $10-20K. How much fuel would $10,000 get you?? Probably enough fuel to last 10 years. I'm just playing the devils advocate here, but I'd hate to see you ditch the 340 for a few MPG. All I'm really saying is to do the math and see if you'll really save any $$ in the end. Oh, and I Love 360's don't get me wrong.

 

[rumblefish360]

Yes change the gears or take other measures to boost the MPG (JMO). By the time you add up the expense of changing out the engine plus the work involved, what did you really save. For example. You sell a 30 MPG VW and replace it with a 40 MPG Prius. The extra expense is $10-20K. How much fuel would $10,000 get you?? Probably enough fuel to last 10 years. I'm just playing the devils advocate here, but I'd hate to see you ditch the 340 for a few MPG. All I'm really saying is to do the math and see if you'll really save any $$ in the end. Oh, and I Love 360's don't get me wrong.

To an extenet, I agree. Since the OP (1975sport) can make a swap easy enuff, it is the mileage he is after. The swap and down time are easy.

Arguing over this is stupid. This happens every time someone tries this. Theres allways someone coming on going "Wait" or "Your anidiot" or something and totaly ignoring the help being sought.:banghead::violent1:

 

[dodge freak]

that's why i been keeping the rusted out-worn out 92 olds, why buy a newer car when this one gets me around town just fine? Someday the frame will crack, trans will wipe out--something bad $$$$ and then it be gone. I was told 3 years ago the car isn't going to make it another year..last Feb the exhaust got loud and I took it across town to a shop and they fixed it but didn't like the slow brake line leaks and "accidentally" caused 2 lines to leak very bad and a front hose to crack. They claimed it was too rusted out to put on a frame hoist to remove the wheels. So V Day weekend it got towed home and me used a floor jack to lift and repair it--so much for my strip club weekend, ha ha ( i was taking it in so I didn't get pulled over during the wee hours coming back home)

I need to change that oil again, been over 6 months, yuk

 

[OwdKasd]

I would never call someone an idiot. All I wanted to say is do the math and see if the swap would really make sense. I just know that when I was young I was penny smart and dollar foolish. Now at 46, I'm just starting to be able to see the big picture when I spend money to save money. I just wanted to try to help him think it through a bit. I truly hope my input might help even just a little bit. Good luck on the decision! You'll definitely have fun either way you go.

 

[dodge freak]

BTW i think 20 mpg is good enough, crazy to get 30--40 mpg. I think I always be driving 20 to 50 year old cars...I was at a car show this summer and some very old man comes chugging in with a model T in fair shape..I thought to myself that might be me in 40 years, driving around in a car I learned how to drive in

 

[dusterny]

My 71 Duster has LC 360 and I get over 16 mpg without any problem. My 360 has a small cam,steal shim headgaskets,600 Holley carb and runs 3.23 pegleg. I drove 153 miles last Sat and just squeezed 9.3 gallons into it. If I wanted better milage I think there is some more to be had. I think it can be done if 18-19 is what your lookin for IMHO.

 

[dodge freak]

You know an Eddy/ Carter 500 carb would likely get a bit better mpg and there is 2.94 gears--I think I heard you can go too steep and the motor will lug and get worst mpg in stop and go driving. A lock up TC would help also.

Mopar was showing MPG ratings of 23 mpg in 1980 on its full size sedans, some did have 2.45 gears thou--but then all that smog stuff which hurts mpg.

Ugh, if $8--$10 a gallon fuel comes around soon--it might--well I don't wanna think about it but yeah high teens is a maybe...hopefully we get some higher octane pump fuel so a true 11 to 1 compression with iron heads would be possible...well if the gov wants 56 mpg come 2025 maybe they will sell better fuel to help get it.

 

[1975sport]

Where's the old 340? :-D

Last time i saw it a guy was running it in a 60 belvedere in the demoltion derby.

 

[krazykuda]

My dad had a 76 Charger that got 20 mpg on the highway stock.

I was reading a tech book by Larry Shephard where he stated that the original cam from the stock 360 2 bbl was the best cam for fuel economy. It has 252/258 intake/exhaust duration and .410/.412 lift. I haven't gotten to try this cam yet personally, but am looking to find one and try it in the future.

I have used a stock 340 cam 268/276 .429/.444 with Rhoades variable duration lifters, 9.2 compression, stock cast iron 4 bbl intake, Holley 600 vac secondary with electric choke, stock exh manifolds, and dual exhaust and 2.76 axle ratio. this combination got 17 3/4 MPG highway and good performance. I had to upgrade the axle to 8 3/4 eventually after breaking three 7 1/4 axles.

I would recommend using the 360 as is with the original cam. Maybe throw in Rhoades variable duration lifters. You could use the 2 or 4 bbl carb. I have found if you go to a dual plane 4 bbl intake with a 600 cfm vacuum secondary carb with ELECTRIC CHOKE (Holley 80457 out of the box or an Edelbrock with electric choke) and electronic ignition, makes for a great daily driver. The carbs run $280 at Mancini racing. The trick is to make sure you hook the electric choke up properly to a 12 volt source (not off the coil). I used the input side of the ballast resistor. Then set your choke properly. I could go out and start the car in middle of winter in Michigan by just giving two pumps of the gas pedal and cranking it over. It would fire right up and as soon as I got good oil pressure, put it in gear and start driving without any hesitation or stumble.

I caution you on the headers. I used to run Hooker super comps and they hung below the k frame on the drivers side. Eventually the low hanging pipes would get crushed over 50% from going over pot holes, high curbs, and speed bumps. Then they do not flow very well in that condition, so I went back to stock exhaust manifolds. You could use the old stock 68 - 70 340 manifolds, but they pull a good price (350 -700 bucks) if you can afford them for good exhaust flow. Definately use dual exhaust.

So quick in a nut shell. Run the stock 360 cam and put a 4 bbl dual plane intake with 600 cfm carb and run electric choke and electronic ignition and 2.76 axle ratio. This will give nice driveability even in winter and good fuel economy maybe 17 to 21 MPG in your lighter a body (if you control your urges to put the pedal to the floor). You won't get good gas economy if you keep putting the pedal to the floor. Use self control if you need the economy, But it is nice to stomp on it and go fast now and then if you have the extra gas money.

 

[rumblefish360]

My dad had a 76 Charger that got 20 mpg on the highway stock.

I did it in my '79 360 Dodge Magnum. More on it later........

I was reading a tech book by Larry Shephard where he stated that the original cam from the stock 360 2 bbl was the best cam for fuel economy. It has 252/258 intake/exhaust duration and .410/.412 lift. I haven't gotten to try this cam yet personally, but am looking to find one and try it in the future.

Thats the cam I had in the engine, being it was an OE 2bbl.

if you can afford them for good exhaust flow. Definately use dual exhaust.

I used duals off the exhaust manifolds.

So quick in a nut shell. Run the stock 360 cam and put a 4 bbl dual plane intake with 600 cfm carb and run electric choke and electronic ignition and 2.76 axle ratio. This will give nice driveability even in winter and good fuel economy maybe 17 to 21 MPG in your lighter a body (if you control your urges to put the pedal to the floor). You won't get good gas economy if you keep putting the pedal to the floor. Use self control if you need the economy.

This is basicly what I had in my Magnum.

OE air cleaner the unit with the trap door/flapper in the pan. Off of a 340. Also a K&N filter. It was on top of a iron '79 egr equiped 360 intake and a Carter 625 AFB. Dual exhaust off the OE manifolds @ 2-1/2 with an H pipe into twin cats (Needed at the time) & Thrush mufflers. Pipes to the bumper.

I picked up a junk yard electronic vacuum advance distributor and use a Chrome box. While the box was good, I switched over to a MSD for added mileage. No real performance gain in high speed, but mileage did indeed improve.
With the 2.76 ratio and 235/60/15's on all 4 corners, 20 mpg's was doable with a light and constant foot.

IMO, mileage improvers to the combo I had would have been;

Aluminum LD340
Headers
(In a E or B body, the super comps do not hang low or run under the steering linkage.)
A head milling for a higher comp ratio. The OE 7.8-1 was bad. A 9.0-1 would have been much better.
An electric fan over the MP viscous could have show an improvment.
Taller tires. I would have like to try 255/60/15's at the back.

IDK about a set of Rhodes lifters helping much here being the cam is small. Maybe, IDK, the price of lifters and gaskets is under $200. You could try it! The experiment could show something maybe?

 

[65CudaFish]

My 71 Duster has LC 360 and I get over 16 mpg without any problem. My 360 has a small cam,steal shim headgaskets,600 Holley carb and runs 3.23 pegleg. I drove 153 miles last Sat and just squeezed 9.3 gallons into it. If I wanted better milage I think there is some more to be had. I think it can be done if 18-19 is what your lookin for IMHO.

Yeah the 570 CFM Street Avenger would get you about 1.5 to 2.0 more miles per a gallon:color:

 

[jerry6]

I'm not sure my mileage but I put in $20.00 and drove 78 miles , this was at 1.43/litre . this was in traffic on the highway , plus 20 minutes of idling while I filled the rad and made sur nothing leaked . Latest trip went 239 miles on $60.00 1/5 city / 1/5 back roads the rest highway with a few blasts into jail territory , on empty stretches of highway .

Right gears , set up properly you could see 20 mpg +