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post #1 of Old 05-23-2010, 07:34 AM Thread Starter
JeepLawyer
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1979 CJ7 
 
Join Date: Mar 2002
Location: near Conway, Arkansas
Posts: 37
Mileage for: CJ-7 304 V8? 11 mph?

I have a 1979 CJ-7 with the AMC 304 V8.

My jeep dealer replaced the plugs, cap and rotor, plugs, spark plug wires and vacuum lines in a major tune up, and completely rebuilt the carburetor, tuning it so it would use less gas to the extent possible as well.

I am getting 11 mph on the last two tankfuls since. Note that this is a combination of freeway driving, trail driving in 4 wheel low on occasion but usually 4 wheel high... just a good average of how I drive in a give week. I only use the jeep to go to the post office, cafe and then off road practically every day with an occasional trip 20 miles on the freeway... pretty average driving for me and not what you think of as a commuter since my office is here on our property.

How is this compared to your CJ with 304 V8?

I guess it is a lot better than what I was getting but I was hoping for more.

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post #2 of Old 05-23-2010, 07:43 AM
BioTex
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2006 TJ Wrangler 
 
Join Date: May 2008
Location: Alpine, Tx.
Posts: 3,173
My 85 has a 78 304 in it. 2K since rebuild. I run 3.73 gears and 12.5 x 33" tires. I get 15mpg running down the highway at 65mph consistently.

I run an RV cam from Summit, and installed the Team Rush upgrade. You should check into the TR upgraded cap and rotor also. Bet you would gain a minimum 1 mpg.

Can't comment on MPG when trail riding. Most of the stuff I do is extreme. I can run all day in 4 Low on a tank.

'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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post #3 of Old 05-23-2010, 07:45 AM
243
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1978 FSJ Cherokee 
 
Join Date: Sep 2002
Posts: 3,356
I was getting 10 mpg consistently in my Waggie with a 401, QT and 31x50x15's. Highway/City and romping on it quite a bit.

1978 Cherokee, TBI 360/T400/QT...6.0/6L80/NP241C in the works...
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post #4 of Old 05-23-2010, 07:46 AM
Jeeper75
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1975 CJ5 
 
Join Date: Mar 2009
Location: Dayton, Oh
Posts: 74
With my 304 I am getting 10-11 mpg with all city driving.

1975 Jeep CJ5, Dana 30, Dana 44, Rough Country 2.5'' lift, Dana 20 x-fer, T-15 trans, 31's, AMC 304 w/ performer intake. Brad
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post #5 of Old 05-23-2010, 07:49 AM
Trapshooter
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1986 CJ7 
 
Join Date: Mar 2007
Location: Jacksonville, Oregon
Posts: 2,309
I am assuming you have a Motorcraft 2100 carb and still have an AMC 20 rear axle. If your '79 is like mine, you will have a 3.54 gear ratio and a T-150 3 speed Tranny.

The best I have ever seen is 15 mpg. I consistently get 12-14 depending on the type of wheeling I am doing.

All emission devices have been removed from my '79 and I have dual Flowmasters running off the stock exhaust manifolds.

Do you know if your speedometer is reading correctly?

'86 CJ7, 258, Carter BBD, Nutter'ed, TeamRush'ed, T-18, Twin Sticked Dana 300, D30 Frt-Pwr Lok L/S-4.10, AMC 20 Rear-Mosers-Detroit Locker-4.10, 2.5 BDS Lift, 1" Body Lift, 33" Wild Country M/Ts, Black Spoke wheels

'45 CJ2A, L134 Go Devil, T-90 Tranny, Warn O/D, T-18 T-Case, Dana 25 Frt, Dana 41 Rear, 531st CJ made

My 401 build: http://www.jeepforum.com/forum/f8/tr...build-1338277/
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post #6 of Old 05-23-2010, 07:51 AM
BioTex
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2006 TJ Wrangler 
 
Join Date: May 2008
Location: Alpine, Tx.
Posts: 3,173
Good point on the speedo reading properly. I had to correct mine when I ran larger tires.

'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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post #7 of Old 05-23-2010, 08:11 AM Thread Starter
JeepLawyer
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1979 CJ7 
 
Join Date: Mar 2002
Location: near Conway, Arkansas
Posts: 37
The jeep is completely stock on the gears, transmission,to my knowledge. I am running 31.5" tires, Goodyear MTR I's. It is not lifted. I do not know if the spedometer is accurate. It is at 41,000 miles. The sending unit on the gas tank is probably off as when it reads 'empty' I fill it up and only put in 7.2 to 8 gallons. I am assuming itis a 10 gal tank? As you all can tell, I am in the 'learning stage' about CJ's by what I am writing and reading here. I have had 7 new Wranglers during my lifetime. This CJ beats them all as far as clearance, power and uniquenss as had 4 cylinders mostly!

So, I am computing mileage with 7-8 gallon fill ups.

Gotto leave now will read morelater.Thanks!
Robert
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post #8 of Old 05-23-2010, 08:26 AM
Trapshooter
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1986 CJ7 
 
Join Date: Mar 2007
Location: Jacksonville, Oregon
Posts: 2,309
Robert, the stock fuel tank is 15 gallons.

The best way to check you speedometer is with a hand held GPS. If you don't have one grab a friend who does and take them for a ride in your CJ. Once we have that info we can determine your actual mileage.

'86 CJ7, 258, Carter BBD, Nutter'ed, TeamRush'ed, T-18, Twin Sticked Dana 300, D30 Frt-Pwr Lok L/S-4.10, AMC 20 Rear-Mosers-Detroit Locker-4.10, 2.5 BDS Lift, 1" Body Lift, 33" Wild Country M/Ts, Black Spoke wheels

'45 CJ2A, L134 Go Devil, T-90 Tranny, Warn O/D, T-18 T-Case, Dana 25 Frt, Dana 41 Rear, 531st CJ made

My 401 build: http://www.jeepforum.com/forum/f8/tr...build-1338277/
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post #9 of Old 05-23-2010, 09:54 AM
Drednot
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1991 YJ Wrangler 
 
Join Date: Aug 2005
Location: Phoenix
Posts: 3,240
Most likely your speedo is off as your tires are much larger than the 215-15s it most likely came with.

Take it out on the freeway and check your odometer reading against a run along ten milemarkers. That will give you a convenient conversion factor for your mileage calculations.

91 YJ Sahara, 4.0L, AX-15/NP231, D30/D35@3.07
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30M/8.25@3.73
Emission test=YES
"Non Vi Sed, Arte"
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post #10 of Old 05-23-2010, 10:18 AM
Andy5150
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2003 TJ Wrangler 
 
Join Date: Nov 2005
Location: Palm Harbor, Fl.
Posts: 659
I get 11 to 11.9 mpg with a 360 in a cj-7. I have 4.10 gears, 32" all terrains, and a t-18( no overdrive). I would think you should be doing better with a 304.
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post #11 of Old 05-23-2010, 11:40 AM Thread Starter
JeepLawyer
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1979 CJ7 
 
Join Date: Mar 2002
Location: near Conway, Arkansas
Posts: 37
Drednot's suggestion is a good start; i was assuming my odometer is right and need to check it.

As a side question: If I go to the trouble to have the gas tank dropped to replace the sender unit (which incidentally suddenly the gas gauge started being off, after being fine in the several months I had it in which I was getting it in good condition, e.g., everything working and until now never checked mileage)... can you replace the 15 gallon tank with a 20 gallon tank without affecting clearance, etc. -- since if I am having the tank dropped anyway, it is a thought.... or maybe just have the sender unit replaced...

Thanks all.
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post #12 of Old 05-23-2010, 04:17 PM
flaugher
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1979 CJ7 
 
Join Date: Oct 2007
Location: West Virginia
Posts: 24
Tired 304 in my stock '79 CJ7, new carb... consistently 10-11 mpg.

1979 CJ-7, AMC 304
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post #13 of Old 05-23-2010, 04:42 PM
lars0909
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1977 CJ7 
 
Join Date: May 2009
Location: western Colorado
Posts: 21
I did the Team Rush upgrade on my 77 CJ. New distributor, large cap, MSD wires and coil with a Summit box. No emission stuff. Hedman headers and mufflers. 31's and 4:10 gears. Went from 13 to 17+ in all around driving. The Team Rush was the best thing I have done to CJ to date. Highly recommend it.
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post #14 of Old 05-23-2010, 08:20 PM
Trapshooter
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1986 CJ7 
 
Join Date: Mar 2007
Location: Jacksonville, Oregon
Posts: 2,309
Quote:
Originally Posted by JeepLawyer View Post
Drednot's suggestion is a good start; i was assuming my odometer is right and need to check it.

As a side question: If I go to the trouble to have the gas tank dropped to replace the sender unit (which incidentally suddenly the gas gauge started being off, after being fine in the several months I had it in which I was getting it in good condition, e.g., everything working and until now never checked mileage)... can you replace the 15 gallon tank with a 20 gallon tank without affecting clearance, etc. -- since if I am having the tank dropped anyway, it is a thought.... or maybe just have the sender unit replaced...

Thanks all.
You can go to a larger fuel tank but it will affect clearance. The larger tank hangs down farther than the stock 15 gallon. This may not be an issue depending on the type of wheeling you do.

'86 CJ7, 258, Carter BBD, Nutter'ed, TeamRush'ed, T-18, Twin Sticked Dana 300, D30 Frt-Pwr Lok L/S-4.10, AMC 20 Rear-Mosers-Detroit Locker-4.10, 2.5 BDS Lift, 1" Body Lift, 33" Wild Country M/Ts, Black Spoke wheels

'45 CJ2A, L134 Go Devil, T-90 Tranny, Warn O/D, T-18 T-Case, Dana 25 Frt, Dana 41 Rear, 531st CJ made

My 401 build: http://www.jeepforum.com/forum/f8/tr...build-1338277/
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post #15 of Old 05-23-2010, 08:36 PM
PERK
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1983 CJ7 
 
Join Date: May 2007
Location: LIVERMORE
Posts: 692
fill out your profile. What transmission and transfer case do you have?
aftermarket 21 gal. tanks hang lower than stock 20 gal. tanks
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