View Full Version : 3.9L 4bt cummins
09-04-2005, 07:40 AM
I need as much information on this engine and engine swap. I think the main reason I am holding off on actually finishing making my 74 cherokee road worthy is cause I know of the enevitable -12MPG I will get. I have done some research and it seems like this could be a easy swap. I dont really care about money as much as I care about how much fule I will burn in my 360. I am kind of a hippy when it comes to fuel economy. I am all about not doing my part in destroying the enviroment.
This swap seems popular in the m715 crowd. I am not too worried about having a ton of power. This will be driven all over...80%/20% street/trails. I figure if this engine can move a cab over truck well enough it should move my FSJ brick! hah
I just want to know if it needs a adaptor plate to adapt the 3.9L to my transmission. Will I need to get a new transmission also?
My main goal is to have a clean burning low MPG FSJ cause I am totally in love with everything (but the engine) that my jeep is.
So what I need is some links...or whatever. I see the engines selling for brand new on ebay RTR (ready to run) for about 5 grand. thanks ahead of time
09-04-2005, 01:39 PM
ever consider using a GMC 6.2 or 6.5?
09-04-2005, 01:43 PM
The only way it's going to be clean burning is if you convert that diesel to run on vegetable oil. Otherwise, its not any noticably cleaner than a gas motor in tune.
09-04-2005, 03:09 PM
You would need to use a different Trans, or at least I think it would be cheaper to do so Adaptors are always expensive. If you want to stay Auto then you could use a TF727 and a Dodge NP205 or NP208 T-Case. If you want to run an OD Trans then you could rob one out of a Dodge Diesel equiped with a OD trans. Standard trans would also be an option as well. You would have many options to look at.
09-05-2005, 01:21 PM
An EFI diesel does burn cleaner than an EFI gasoline. An NV4500 is the easiest trans to bolt up, if its from a dodge truck as I recall. MInfantry did this swap in his M715. With a 4BT, you can expect 20-25mpg.
09-05-2005, 01:47 PM
Heck, I get, or since it is wrecked now, had gotten up to 22 mpg on my 6.2 in my J20
09-05-2005, 03:17 PM
From Grinning Planet (tree hugger site) "Because of their lower per-mile fuel consumption, diesel engines generally release less carbon dioxide—the heat-tapping gas primarily responsible for global warming—from the tailpipe. So that's a check on the good side of the pollution chart. But when it comes to smog-forming pollutants and toxic particulate matter, also known as soot, today's diesels are still a lot dirtier than the average gasoline car."
and there is also this...
"Making a gallon of diesel fuel requires 25% more oil and emits 17% more heat-trapping greenhouse gases than gasoline reformulated with MTBE. Similarly, diesel requires 17% more oil and emits 18% more heat-trapping gases than gasoline reformulated with ethanol. This means that diesel fuel's advantages from its higher per-gallon energy content and better performance on greenhouse gases are partially offset by the impact of diesel's fuel-production process."
Since the environment is a concern have you ever thought about propane or ethanol (E-85 or E-95) conversions? Since enviromental concerns Converting to either would save you money on drivetrain swapping. Plus you could always add and overdrive tranny into the mix. Producing better economy. And either conversion (including a complete rebuild of your 360) would be way cheaper than $5,000 for just a motor.
09-05-2005, 03:34 PM
How is it diesel requires more oil to make than gasoline, when diesel comes out of the boiler before gasoline? IE: Gasoline has to be further refined, meaning less of that material makes it into the final fuel. They may be right in this, but from what I have read its the opposite.
09-05-2005, 03:39 PM
The information came directly from the EPA's studies. I don't know why it's that way either. But no matter how ya look at it, diesel and gas will still have to come from oil that originates in some foreign land. So if somebody is dead set on converting from gasoline, why not go to something like E-85, propane, or natural gas (way to expensive now) and support local economies instead of big oil companies and Arabs?
09-05-2005, 03:43 PM
Here's a link for more info...
09-05-2005, 04:12 PM
Well if you speak of it that way, propane comes from the same oil as well. Just a different part of the oil (it is petroleum based just like gasoline and diesel). CNG is not the way to go, since natural gas reserves are *FAR* lower than oil reserves.
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