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Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.
I would like to hear some different set-ups that people have, that has improve their gas mileage. I have a 1978 CJ7 with a AMC 258 i6 / 4.2l 1 barrel carb running on 33x12x15. It love the gas.
How tight is the budget?? the distributor, it you already have an autolite distributor is less than $AMC 150 ,Team rush TFI. If you could do a 4.0 head with aluminum two barrel manifold and 4.0 exhaust you would have covered most of the desirable engine mods. If you just want to replace the cast iron intake, take pictures of what you have, I may have one.
Work on your ignition and get the most timing advance out of it possible. Make sure the vacuum advance works correctly. My AMC 258 i6 / 4.2l with the carter 2bbl, 33 inch tires with lift got 17 mpg highway all day long.
First off: find the optimum final gear ratio so that the engine RPM is at max efficiency at the speed that you usually drive. Simple as pie, right?
Driving style helps. The old adage about pressing the gas pedal as if there is an egg between your foot and the pedal really does work.
If it is a stick you can keep it at the sweet spot of the RPM's more easily.
Driving like a diesel helps. Just playing around I short-shifted the 6-spd stick in my KJ at 1800-1900 RPM's and can get nearly 19 mpg city that way...but it is a pain in the arse and everyone behind you will hate you.
Biggest thing I have ever done to help the performance and MPG of an AMC is switching to a GM-style HEI ignition. Better than the TFI IMHO.
If you haven't re-geared I'd say the tire height is killing you.
'79 Jeep CJ7 Renegade with 304ci V8, TH400 auto, Quadratrac T-case, Stock 20 and 30 rears with no mods yet, not sure of the gear ratio.. 4" Softride Superlift, w/widetrac shock towers and 35x12.50x15 BFG Mud-Terrains
'76 CJ5, 232 ci, T-150 3-speed, D20 T-case, Corp. 20 rear w/full float axles and lockout hubs and Detroit auto locker, D30 front w/lockout hubs, gear ratio is unknown..
1978 CJ7
Silver paint with black hard top on 33" radials & eagle alumium rims. Good looking ride and have done lots of work to make it look and run great.
Stock equipment is 258 carb, power brakes, power steering, hard top & hard doors (per vehicle gross weight) tilt steering wheel, big brake package with large rotars & drums, T18 Trans with low 6.4 granny gear, Dana 20 transfer, Dana 30 front axle, Dana 44HD rear axle with 3.73 gears. True Trac ft & rear.
I was around jeeps in the 70's and drove a 1973 Jeep Truck. My family had 4 jeeps at the time. We also joined a jeep club back then too. So about 6 years ago looked for a Jeep CJ and found the vehicle above.
I would like to hear some different set-ups that people have, that has improve their gas mileage. I have a 1978 CJ7 with a AMC 258 i6 / 4.2l 1 barrel carb running on 33x12x15. It love the gas.
Saw you tried to send a PM, sorry I just leave it full, and stay on the forum pages for the most part.... Please tell us more about your capabilities??? and what you can do mechanicly? and have you worked on cars/jeeps in the past... Please tell us more about your CJ, how well is it running, miles on it, compression test, overall health, pictures....
I mean.... these things are 35 yrs old, if the engine is not healty, will not get the performance and mpg of a new vehicle... Also your capabilities will also lead us in directions more than others...
I have a 1978 just like you, and you have some good stuff on there....And some stuff that could change...
So I guess we let you collect your info on CJ, get some pics of engine bay top, both sides, and front, and tell us more about you/cj.
I will offer this... 1978 will have a Ford DuraSpark Distributor if stock and you have the BEST one as for mech limit slots for your advance. There is NO WAY I would swap out that distributor to another one. You have the version I tell all others to look for.... You have limit slots of 13r and 18r and will be set at 13r at the factory..... If healty engine we can change to 18r and that will give more advance at higher rpms and max your mpg. You will most likely have 3.54 gears in axles, 1:1 top gear and run 2400 rpms at about 60 mph, you can get 20 mpg an..... but if not healthy engine.... may not be a good idea....
Areas of interest in blurbs... YOu have cast iron intake/exhaust that are attached. 1980 Intake and Used header will both have 1/2" flanges and can help your engine breath better, If healthy changing to the 18r slot can increase mileage and pep (but there is a process), Clogged Idle Tubes on Carter can waste fuel and cause stalls at stop signs/lights. Carter carbs need rebuilds kits every few years and idle tubes need to be drilled out.... Ignition and Header and Good Carb or Carb Work are the areas that will help mpg / pep considering bang for buck... TeamRush, ground DuraSparkModual, ground Head, Copper Antizeise on Plug Threads, are tune up things that can give you 20% mpg/pep with just few simple changes and tune up parts....
I got 23 mpg with jeep truck in 70s and my CJ gets 23 mpg hwy now... Had 3.54 gears with 3 spd on T-18 (4th is granny) and I changed to 3.73 and less lugging so now I can change to the 18r slot, and recurve my dist and rejet my carb to take advantage of my gear change..... It all works together..... 3.54 is right on the edge with 33" tires but it can be done.... 32" might be better. Driving with vac gauge after you work can teach you to drive for mpg MAX.. Changeing gears is expensive and i did not do, had shop do it. I also had front ring gear with 2 theeth damaged, wanted lockers ft/rear and wanted 3.73 or 4.10 gears. Granny gear allowed me to go 3.73 and still have some low gears for off road.... my hyw mileage is excellent...but i tweeked pretty good see bio
do the pics, do a hot compression ck, and show pics of the spark plugs for #1 front to #6 back one and then we can recommend some paths and links to look at..... This take some capabilites and tools.... time light, vac gauge, knowledge are things you need to touch on an discuss. I can lead you to write up that are done already....... If you engine has 200k and compressions in the 90 range not a lot we can do or should do....
Sorry, it is in three different post. I hate computer most of the time. I am glad that i am able to use this form cause it has been a lot of help to me.
1978 CJ7
Silver paint with black hard top on 33" radials & eagle alumium rims. Good looking ride and have done lots of work to make it look and run great.
Stock equipment is 258 carb, power brakes, power steering, hard top & hard doors (per vehicle gross weight) tilt steering wheel, big brake package with large rotars & drums, T18 Trans with low 6.4 granny gear, Dana 20 transfer, Dana 30 front axle, Dana 44HD rear axle with 3.73 gears. True Trac ft & rear.
I was around jeeps in the 70's and drove a 1973 Jeep Truck. My family had 4 jeeps at the time. We also joined a jeep club back then too. So about 6 years ago looked for a Jeep CJ and found the vehicle above.
Sorry, it is in three different post. I hate computer most of the time. I am glad that i am able to use this form cause it has been a lot of help to me.
I like photobucket.com.... the will host your pics and you can use folders that you set up.... Helps because you can use the same pics... over and over.... Click on the address and use the window insert TOOL at the top of the Jeep-CJ.com tool bar. Can also fix the size so it shows up the correct size. Too many of pics on the forum direclty you have to click to make the pic bigger and I do not like that.... maybe a feature to select that pics a bigger pic size like 550x700.....
Can store video and pics there and set up folders... Users can also see you pic and then scan the rest of folder if public folder.... Great for sale items also if you group them all together...
Sorry, it is in three different post. I hate computer most of the time. I am glad that i am able to use this form cause it has been a lot of help to me.
1978 CJ7
Silver paint with black hard top on 33" radials & eagle alumium rims. Good looking ride and have done lots of work to make it look and run great.
Stock equipment is 258 carb, power brakes, power steering, hard top & hard doors (per vehicle gross weight) tilt steering wheel, big brake package with large rotars & drums, T18 Trans with low 6.4 granny gear, Dana 20 transfer, Dana 30 front axle, Dana 44HD rear axle with 3.73 gears. True Trac ft & rear.
I was around jeeps in the 70's and drove a 1973 Jeep Truck. My family had 4 jeeps at the time. We also joined a jeep club back then too. So about 6 years ago looked for a Jeep CJ and found the vehicle above.
Thanks for the pics... look forward to you telling us more about your jeeps operation and some of the stuff I mentioned....
Few things I see in the pics.
Some one changed your exhaust cast iron manifold to a tube header.... Not sure if the intake was changed also but looks like you have 1" flanges on your intake... I will have to look at my old pics to see the stock intake.
The connectory/wire from the distributor comes very close to the #6 spark plug wire.... Lots of NOISE from the spark plug wire and have mag fields build / collasp so push that wire further back twords the fire wall... may help with idle and higher rmps.... That dist is a low level signal wire and needs to be protected....
You fuel line is pretty close to the #1 header.... Maybe lift or tie wrap away from the heat to cool off the fuel some will also help with vapor lock on hot days will keep the fuel from bubbling and causing air pockets.... Also less likely to melt fuel line and cause a fire.....
You have the little cap/rotar and older spark plug wires so the TEAMRush and aux grounds would be a nice upgrade for your CJ. Also the spark plug wires esp old ones.... cannot touch each other or any metal parts of the engine........ Do not get any parts yet, lets get the rest of info first...
I would like to see more info we mentioned above... the compression test is one of the most important..... Tells us the health of engine and how much we should do or not do.... It will take some time to write it all out but you will get better results
I think it is a 5/16 steel brake line that will thread into the fuel pump so you can go up over the top of the valve cover with a ridged line up to the filter. You don't seem to be using a return line from the carburetor, I think this will cause a bit of a problem with the carter 1 barrel. Here are a couple pics of a steel fuel line.
Here are a couple shots of the bottom of the 2 barrel cast iron intake I had on my 77 AMC 258 i6 / 4.2l
computer most of the time. I am glad that i am able to use this form cause it has been a lot of help to me.
