360 gas mileage tips? - JeepForum.com

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post #1 of 23 Old 08-30-2009, 07:20 PM Thread Starter
cracked91
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360 gas mileage tips?

I am getting maybe 10mph with my 360, 12 if I keep my foot out of it.
78 CJ5, 3 speed manual, t15a, not sure of the gears

Suggestions, tips, secrets?

I am gonna start running 1.25 oz acetone ever 5 gallons of gas (can't hurt anything and some swear to it),
change my rear diff oil and tranny oil, make sure my tires are inflated properly

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post #2 of 23 Old 08-30-2009, 07:24 PM
rixcj
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I think you're getting as good as you're gonna get. I got that with my 401, and also with my 360.

From what I've read, that's about the norm.

You've probably got 3.54 gears.

But...it doesn't hurt to try new things, like you suggested that you'll do.

Let us know how you make out.

Rich

'79 CJ5, AMC 360, t-18/d20 twin stick, dana 30/amc20(Mosers), Edelbrock Performer intake, Holley 600, ps/pb, DUI HEI, 'glass tub/1pc. tilt nose, 33x12.50 BFG AT's.

There's a fine line between "hobby" and "mental illness".
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post #3 of 23 Old 08-30-2009, 08:11 PM
John N
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Things I've found that work....

Quote:
Originally Posted by cracked91 View Post
I am getting maybe 10mph with my 360, 12 if I keep my foot out of it.
78 CJ5, 3 speed manual, t15a, not sure of the gears

Suggestions, tips, secrets?
Let's see.....
Leave it parked.
Try to drive downhill as much as possible.
Try to drive with a tailwind.
Let someone else pull you with a strap.

Give me some more time, I'm sure I can find more helpful suggestions. Realistically, putting an upgraded ignition (DUI) and a Howell TBI injection works pretty well for me, but it'll only be a little better.

Otherwise, drive it and enjoy it.

'81 Scrambler w/ FI 360 AMC, 33x12.50 BFG M/T's, 5" of lift, ARB'd Dana 44's F & R, Dana 300 clocked & twin sticked w/4:1, Warn XD9000i, etc...
2002 Grand Cherokee Limited, 2008 Overland Grand Cherokee, a 1976 CJ-7 in pieces and 3 more off-brand 4x4s...............
John N
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post #4 of 23 Old 08-30-2009, 08:29 PM
84cj
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With the 360, t-176, 33's and 3.31's, I would get 18 mpg. Well tuned and foot out of the carb, well, most of the time. Verified with GPS, BTW.
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post #5 of 23 Old 08-30-2009, 09:59 PM
jeepdaddy2000
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10 is too low. If you are really serious about mileage than you need to be willing to so some things. First you need to find out what gears you are running. Next, drop a tach into it and take a drive down the road. Check your RPM's against your ACTUAL (not what is on your speedo) speed and get back to us. Too tall gears coupled with large tires will just keep your foot deep in the carb and waste fuel.
Insure your engine is in good mechanical condition. A low cylinder, sloppy timing chain, or worn cam can gobble fuel. You will need to do a complete tune up. This will include bumping the timing up a bit. Insure your carb is OK. Don't know what your running (you need to fill our your profile), but such things as blown power valves and poorly adjusted chokes can take a toll on your mileage. Make sure your running a good 180 or higher thermostat.
Lastly, in my experience, the biggest factor is driving habits. You need to push the accelerator pedal as if you have an egg under your right foot. Slow down and coast to stops instead of gassing it then slapping brakes. Lower your overall speed. Dropping from 70 to 55 will make a huge difference.
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post #6 of 23 Old 08-31-2009, 09:58 AM
Pathkiller
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I agree that 10mpg is too low for a CJ-5 with a 360. I had a 78 Cherokee (fullsize) with a 360, factory 4bbl (Motorcraft 4350), TH-400 (which is itself a pretty parasitic drag) and Quadratrac fulltime case and it routinely got 14-16mpg highway. It had 3.73 axle gears too. Your setup should beat that by a considerable margin since the CJ is about 1,000lbs lighter than an SJ. What carb are you running? Check the following: 1) What tires are you running? Is your speedometer accurate? Have you verified it by GPS? 2). Check your timing, fuel mixture and carb jetting. Running too rich means you're just dumping raw fuel out the exhaust. A reasonably sized vacuum secondary 4bbl carb should be a little more fuel efficient than a large 2bbl as the primaries are smaller (just do your best to keep your foot out of it!). 3) Check your driving style. You recognize a difference when you keep your foot out of it. Getting good MPG has a lot to do with driving habits. There are numerous tips on changing your driving style for better MPG, so I wont' spell them all out here, but it's worth checking it out.

IMHO, adding acetone is a really poor solution. I challenge anyone to produce a credible scientific, repeatable experiment showing the benefit of supplemental acetone in gasoline. Complete bunkum. Even if you are okay with the corrosive aspects of acetone (destroying o-rings, rubber fuel lines and other fuel system components as well as dissolving any paint it touches), do you save enough gasoline to justify the cost of the acetone itself?
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post #7 of 23 Old 08-31-2009, 10:33 AM
JeffJ
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I get about 12 mpg with my CJ7 with 360, Auto Trans, 4.10 gears, 33" tires.

'85 CJ7, AMC 360, Auto, D300. 33" with 4" lift. AMC20 Trussed w/4.10 and Truetracs, front Dana 30 w/4.10 and Truetracs.
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post #8 of 23 Old 08-31-2009, 04:18 PM Thread Starter
cracked91
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well its not city driving thats bothering me, its highway driving. The fact that even pressure (fairly even) on the gas for multiple hours is giving me such poor mileage.
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post #9 of 23 Old 08-31-2009, 08:33 PM
cj7Sswampers
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you could not have a 360......

P$yCh0--82' CJ7--Chevy 305--T-176--Dana 300--39.5" Super Swamper TSL's--12" lift--S.O.A. Conversion--Old Sarge
EVERYTHING IS SUBJECT TO CHANGE
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post #10 of 23 Old 08-31-2009, 09:38 PM
berserker
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10 is a bit on the low side. I got 11-12 with my 360 and T-150 in my 79 CJ-7. I have a 360 in my '86 and am now getting 13 with the 5 speed T-5. I'm running 31's with 3.31 gears, and a Quadrajet 4bbl. I've heard you can get better mileage with a 4 bbl because it is a more efficient carburetor, but you have to avoid opening up the secondaries frequently (which I have a habit of forgetting).

Ignorance can be fixed, but stupidity is forever.
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post #11 of 23 Old 09-01-2009, 12:46 AM
OldSailor
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Quote:
Originally Posted by cracked91 View Post
I am getting maybe 10mph with my 360, 12 if I keep my foot out of it.
78 CJ5, 3 speed manual, t15a, not sure of the gears
When I still had the MC2100 carb on my CJ7's AMC 360, I got a little over 14 mpg with 4.56 gears and 35" tires. TF999 tranny, with lockup circuit blocked off. I had an MSD 6AL ignition on it at the time.

1977 CJ7, AMC360 V8 w/ headers, DUI HEI, Edelbrock intake, Holley 4150 carb, , TF999, D300, D30 front and AMC20 rear with 4.56 gears and lockers both ends, 4" susp lift, 2.5" body lift, 35" BFGs, ARG steering, 8000-lb winch, etc.
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post #12 of 23 Old 09-01-2009, 06:34 AM
fwlslyr
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Damn I wish I got 10 mpg. I'm doing something less then 5 in four low off road. Might be closer to 3 mpg.

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post #13 of 23 Old 09-01-2009, 12:12 PM
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Quote:
Originally Posted by berserker View Post
10 is a bit on the low side. I got 11-12 with my 360 and T-150 in my 79 CJ-7. I have a 360 in my '86 and am now getting 13 with the 5 speed T-5. I'm running 31's with 3.31 gears, and a Quadrajet 4bbl. I've heard you can get better mileage with a 4 bbl because it is a more efficient carburetor, but you have to avoid opening up the secondaries frequently (which I have a habit of forgetting).
You must really be featherfooting the skinny pedal if you're running a T-5 with that 360.
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post #14 of 23 Old 09-07-2009, 10:58 AM Thread Starter
cracked91
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Well I tuned the carb down a bit and I got about 12 on a 400 mile round trip. Its still running rich though I can smell alot of gas. Think I might put a smaller carb on there? Anyone running the Holley 500 cfm 2 barrel carb?
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post #15 of 23 Old 09-07-2009, 06:11 PM
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Thats about as good as your gonna get. We used to have a old Wagoneer with a 360 about 7MPG city, 10MPG highway. Wagoneers are much heavier that CJs but to me 10-12 out of a 360 in a CJ is good. That Wagoneer was pretty worn out when we traded it, but proved to be a great family hauler.
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