85' jeep cj7 Cummins 6BT Swap
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Thread: 85' jeep cj7 Cummins 6BT Swap

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    Question 85' jeep cj7 Cummins 6BT Swap

    I am currently running an AMC 360 5.9L in my 1985 jeep cj7, this engine has 160 thousand some odd miles on it and gets 13mpg on a good day downhill.

    The driveline consists of the AMC 360, 3spd man., dana 20 transfer case, AMC corporate 20 rear and Dana 30 front. The jeep started its life as an inline 4cyl AMC so it came with 4.10 gears. it is currently sitting on 35 12.50 15 ProComp M/Ts and a 6' spring lift (no shackles, blocks, etc.) just increased arch in the springs.

    I am currently looking at a 91' dodge with a cummins 12 valve, 5spd man. I have seen pics of 6BTs under the hood of cj/yj/tj jeeps so it will fit, although it will be tight.

    Due to the length of the engine i am considering relocating the radiator and running electric fans on it in order to be able to get the engine off the firewall a little. i also know that the engine weighs 950 some odd pounds plus tranny etc. with the arc in the springs and the brick-like ride i have with the v8 i am convinced that the suspension will be the least of my worries. my primary concern is frame reenforcement as well as mount placement, engine height, etc.

    any hints tips or advice would be appreciated.

    i have looked around on this site for a while and havent found too much in the way of people putting 6BTs in CJs but if the price on this dodge is right and i can go form 13mpg to closer to 25ish it would be well worth it.

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    I had the same idea when I wanted a diesel Jeep too. In the end I decided on the 4cyl. I have just started mocking up where to out the engine in the Jeep and I will have it mounted this week. I really think you will have to cut the firewall to get the 6cyl in. Maybe not if you put the radiator in the back of the jeep. I really wanted to run an intercooler too. Weight wise you are looking at around 1150 just for the engine. The 4bt drivetrain will only be about 150lb heavier than your current drivetrain. I am building a driver so I did not want all that extra weight up front on a short Jeep. Does the Dodge you are looking at have the NV4500 or the Getrag trans? If you use a NV then you can find a Dana 300 transfer case and not need an adapter plate. If you are building a driver then you will probably want to re-gear a little taller. Shoot for 1600rpm around 65mph. It depends on what you are after. A 4bt can be turned up plenty for a Jeep, mine 215hp and 550ft/lb. I have ordered one piece rear axles and I am still concerned about it.

    Anything can be done and I would love to see a 6bt in a Jeep. I have found some pictures googling the 6bt in a Jeep.
    Just my .02
    Last edited by bo799; 12-27-2009 at 07:23 AM.
    1976 CJ7 down to the frame
    4bt sitting in the floor next to it.
    Dana 300 sitting under it.
    NV4500 is here now.

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    I have been looking up specs on the 6bt and everything i have found says that the dryweight of it is around 950 to 1000lbs, which is really my number one concern, as i have seen pics of a 6bt in a wrangler and it fit rather nicely with the radiator still mounted in stock location. i really would prefer to use the 4 over the 6 due to the weight differences and the extra room i would have to work around it. if i end up getting this particular dodge then i would like to find someone who would trade me a 4bt for a 6 straight up, all wiring and accessories included (if you know anyone let me know). I am currently waiting on an email from the guy with the truck to verify what transmission it has in it, although everything i have found online has said that a 91 dodge d350 with a 6bt will have the NV4500, i have several transfercases laying around including dana 18, a few 20s, and a 300 off the original drivetrain i pulled out of the jeep with the 4cyl amc 2.5l. what axles and gears do you have in you cj now? as i said before mine have the 4.10s in them from having had the little 4cyl in it from the factory. the jeeps is a daily driver hence the need for better fuel milage.

    I have another cj frame and body tub/panel set that i will most likely use for the mockup for the mounts, reenforcements, etc. as the jeep will be being used up till it is parked for the swap and immediatly after. I don't really know much about diesels themselves at this point i just know that the cummins is the way to go and it is relatively avaliable if you know where to look.

    if i cant get ahold of a 4bt in place of the 6 then ill probably just try and stick that in it.

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    Contact Scott at TN Diesel Conversions. His name on this site is Crewcab59. He does alot of conversions and may be able to help you with an engine trade. He has helped me alot with my conversion. The older Dodge NV4500's had a problem with the nut on 5th gear backing off. All of them did it. My Jeep came with the 304 in it and has 3.54 gears. I have 31in tires and plan on going to 33's when I wear these out. I have an intercooler from a ricer that I am pretty sure I can fit between the grille and radiator. I am trying to stick with the engine driven fan also. My Jeep has a factory skid plate on it and I was hoping I could use it to mount the trans to but it is not even close, it is way to high. I will have to make a crossmember to re-inforce the frame and have a trans mount. The front axles are stock and I just ordered a one piece kit from Crown for the rear. I plan on Dana 60s later when I can afford them. I am after a driver to and only plan on light off-roading. Send me an email address and I will send you some pictures of me starting to fit the engine to the frame. I know the dilema you are facing. I found several Dodge trucks to use as a donor that were the same price as my 4bt. The 4bt is getting more popular and that is driving the price up. Search for a stepvan too. You may find one around that is not to expensive.
    BO
    1976 CJ7 down to the frame
    4bt sitting in the floor next to it.
    Dana 300 sitting under it.
    NV4500 is here now.

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    hey did u ever get that truck with the 6bt?

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    91 wont have an NV4500 unless it is swapped in. 89-93 were getrag. 94-02 were nv4500
    1967 M715 6B NV4500 203/205 doubler HP60/14 4.56s with detroits.

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