The Stovebolt Site Forums The Shop Area The HiPo Shop Opinions on the Jeep 4.0 engine

Got a Jeep in the shop for a complete rewire and it has the 4.0 inline 6. Moved it in and out of the shop several times and the engine is really peppy. Has the T5 trans and with eyes as bad as mine plus the right color paint it could be mistaken for a Chevy 250. Has a 12 port head (not cross flow) with manifolds on the left side like a Chevy. I have one that was in a 30 Plymouth that a customer wanted replaced with a belly button 350 and if you write good things about it I might try to recommend it as a future install for one wanting to stay 6 cylinder.

I had '96 and '99 jeeps with the 4.0 and they were very reliable and lasted a long time (bit of a gas hog though). Those engines have the reputation of being bullet-proof and held in high regard. here's a little history of that motor:

http://www.fourwheeler.com/how-to/engine/154-0604-jeeps-kick-[censored]-engine-history-4-liter/

if you want to read the article, replace the **** in the url with the obvious 3-letter word that goes there. I guess the software filtered out a legitimate english word...

The Jeep engine has an ancestor that goes back into the 1960's, the 232 and later 258 cubic inch engines produced for American Motors by International Truck. They're pretty rugged and reliable. BTW, the AMC V8's from 290 through 401 were also manufactured by International. One of my customers many years ago was a retired foundry engineer who worked for International during those days. He shared a lot of history of the International/AMC relationship with me.
Jerry

My in-laws bought a new Grand Cherokee in the late 90s with a straight 6. I assume it's that same one.

They still have it. Not a lick of trouble from what I know, and they actually towed a pretty fair sized camper for a few years.

I had a '90 Cherokee with one. Last forever, under-powered, gas hog. Just like our 235s. A T-5 would be a nice upgrade, just like it is for our 235s..

International had no hand in developing the Nash! Sixes. Nor did theyhave a hand in the amc v8. International did buy and use the 258 six during it's death in the light truck market. I just finished today as a matter of fact. A rebuild on a 1989 258. These are very tough old sixes. Can take a ton of abuse. Can be built with a mix of 4.0 and 4.2 parts to make 350hp. Even now I rebuild a few dozen 258 and 4.0 liter sixes per year. Last fall I built a supercharged 4.0 that's pumping 400hp. It's in a jeep tj. And is a beast. My one and only new rig. Bought in 1988. Is a wrangler. With s 258. 5 speed . Swapped in dana 44 rear. Never rebuilt. 389,000 miles. Best straight 6 ever built.

Also to the OP. The 4.0 never had a t-5. Amc dropped the t-5 in 1986. For 1987 it came with a Peugeot 5 speed. Late in 1988 it dropped that an started using Aisin ax5 and ax15 5 speeds. In the mid 90's Chrysler went with the nv3500.

From a personal standpoint, I like the idea of a Jeep engine in an old 'bolt. But, I thought you would be labeled a Heretic for suggesting anything other than a GM built engine in a Chevy truck. Especially on this sight! LOL.

The Lynch mob may be coming... HAHA!

Whitedog think of this. The absolute baddest sixes in the 50's where the Hudson hornet 308 straight six. Contrary to an earlier comment. The development of this six was The combination of the Hudson and Nash engineers AKA the Kenosha boys. They Wanted to design a modern straight 6 to replace the older flathead sixes of Nash and Hudson. The AMC rambler was the intended use. I don't think anyone would be upset if a Chevy or Jimmy got an example of their efforts. It's truly a great line of engines. The only straight six of American heritage that Survived into this century. Survived 3 corporate owners. And is as common as air. Development started in 1961. First was used in the 64 Rambler. And last rolled off the line in 2007. Pretty close to the small block chevies run in terms of years.

I had an 86 CJ-7 with the 4.0 and a four speed. The engine was pretty good, but the carb that came sith it was terrible! I think this was the beginnings of pollution control, and the engine had about 100 vacuum hoses and valves, and the carb had a weird stepper motor controlled jet that changed the jet size depending on what all of the vacuum hoses sensed. I rebuilt the engine and threw out that carb ASAP. But it did have great low end power. And lousy gas mileage. And it was a [censored] keeping oil from leaking out of the valve cover.

But it was a great vehicle for where I live, would go through anything, manual tranny and manual lock out hubs.

I also had an IH Traveler (sort of between a travel all and a scout, with a removable fibreglass hard top (if you had four people to remove it). Big V8, auto tran, auto lockouts. A monster to drive and park, but it would go anywhere. Got about 8 miles to the gallon!
And getting parts for it was horrible. It seems that IH would make a change, but continue using the old parts until they ran out. You couldn't order by year, you had to get the number off of the part.

Tim

Looks like I did the right thing in asking about it here; many helpful tips. My only experience with this type engine was in the late 60's or early 70's when a taxi company had a fleet of Ramblers with I think (?) the 258 engines. We did the service work on them and I don't remember having to ever do any major upper or lower engine work, just the usual tune/service work. One thing I won't forget is the oil filter was on top of the engine and upside down meaning a mess with each filter change.

Bluesman. That 86 is a 4.2. And the 86-89 are equipped with the worst carb ever offered on an amc engine! The electronic Carter bbd. And 86 had that horrible plastic valve cover. That went away in 87. A side note.One of The first aftermarket fuel injection ever offered was for the 258 sixes. Howell engineering in 1989 built a kit for the 258 out of GM throttle bodies and computers. All plug and play. These kits are still very popular and all the early 232 and 258 engines benefit from them. The kit is about 1000 bucks new. The 4.0 never had a carb. It first used a Renault based renix system. From 87-90. Then Chrysler developed a replacement for that. That later 4.0 engine then grew in hp. The 95 and up HO engines have great heads. Don't leak. And the only weakness is the factory exhaust header cracks over time. This thread has inspired me to document and post the next 4.0 or 4.2 build and share it hear. Since running 4.0 cores are 100 bucks locally. And the aftermarket support is very strong. These are simple and affordable straight sixes to build. Unlike my 261 in my 60 k10.

Just to clear up a miss-conception on the 4.0 lit.. the YJ Jeep and the late 80's Cherokee were the first to use the 4.0 l it is mpi fuel injected. The 4.2 L was used in all CJ models, it is carbureted.
The T5 trans was used in CJ's in 1982 -1986. That is where the 10 spline input shaft comes from for the in put shaft swap into the T5 so they can fit into our old Chevy pick-ups. The nv4500 was never a oem option
Only the ax15 and it was the latest 5 exp offered. I would go with the 4.0 if I were to do the jeep swap. But only with the engine after it went with the Chryler fuel injection system. Parts are easier to get and diagnostics are friendlier. The Renault /AMC electronics are archaic at best . Just realized I echoed some of the previous post...sorry.