4.0L Power and Efficiency Mods

[TEXAS MUDBUS]

Great. Another dude is asking the internet how to get more power from is 4L. Well, not entirely. And by that I mean, I've done some research, and there are reviews that come from both sides of the fence. What I've noticed is the ones who do a bolt on mod are disappointed bit the ones who do a complete engine mod, and spend a big chunk of change do get some excellent gains. Bit the consensus is, there's no middle ground. You can't just do the cat back exhaust and be happy with the money you spent. And you can't just get a cold air intake.

But, I've read if you let the whole motor breathe better with a completely new exhaust, intake, cam, heads, and then let it drink right with some high flow injectors, you get a whole new animal. But, why stop there? Why not make it a stroker and add in some high compression rings and pistons? Well, yes, that's all internal, costs a lot of money, takes a lot of time, and in the end you have a monster 4 litre inline six. So, congratulations on your newfound bragging rights. But, was it worth it?

Toyota makes a much smaller inline six, the 2JZ Supra motor. It's only a 3.0 but everybody in the tuner scene wants one so they can mess with it and get 2000 horsepower. Has anyone seen an AMC 4.0 get 4 digit power numbers? I haven't.

My point is, leave it alone, or put about 5 grand into makin the motor kinda cool and have a jeep witha loud and powerful tractor motor?

In my particular case, I have an '89 EFI model, which has good injectors from stock but the heads are reportedly the worst, and a next gen 91-96 would trump all. The only reason I've considered upgrading is because the rear freeze plug has popped out and to replace it, the intake and exhaust manifolds need to come off. Upgrade while it's apart, or clean it and put it back on?

Tell me what you've done, decided not to do, why, and how you can prove any gains or losses.

[Blue Angel]

Very well thought out post brother......

My 1995 Cherokee has a 4.0 with 225K on it. When I picked it up 18 months ago, it ran really rough. Being on a budget, I just began picking away at it and joined a Cherokee forum,]. My biggest gains in power so far came with a complete new exhaust from the manifold to the tailpipe. A nice header would help out some as well. I have a friend with a 1996 and his header makes a big difference.

My next upgrade is going to be changing to the Dodge Neon 4 hole injectors. This is a common upgrade in the Cherokee world and everyone reports nice power and throttle response gains. Just have to have the computer learn the new fuel ratios....

I would go with an aftermarket header, new exhaust, Neon injectors, and possibly source another cylinder head and go through it.

Nice thread.....

[TEXAS MUDBUS]

I've read about the Neon injectors. Supposedly there's a Ford sedan and minivan that's also a direct fit and produces better power, but I can't remember which one. Maybe the Windstar and a Focus or Taurus? Focus rings a bell... Early '00s..

I'm personally leaning towards a full custom exhaust just because that's what I like doing, and the eventual plan for this motor is once it chews up the internals, if ever, I'm gonna put a stroker kit in it. I love the diesel powerbands and performance, so the closer I could get a reliable gasser to that spectrum, the more fun I'll have.

[TEXAS MUDBUS]

1800+ views in a month and only one person can reply? I know tgeres way more than just two people in this club who know something about the 4.0. Who's done what and what works and doesn't work? Was it worth the time or money or effort?

[Blue Angel]

1800+ views in a month and only one person can reply? I know tgeres way more than just two people in this club who know something about the 4.0. Who's done what and what works and doesn't work? Was it worth the time or money or effort?

Facebook has just about killed this forum. And, it is a real shame in my opinion.

[TEXAS MUDBUS]

I think we all saw that coming, but that doesn't explain how this can be seen 1800 times and not a single one would generate a response.

I'm probably going to do a full Gibson 2.5" exhaust with headers, cat delete, and muffler, with a nice stylized tip if not for performance then the sound. When I get time to install it I'll write up a review and comparing it to before and after the install and before and after a cold air intake. Then add in 91-96 heads with some Taurus injectors for a second performance write up. For science!

[texasfrog]

here is my input. want to get 20 mpg and make 350hp on 87 octane without spending 5k? drop in a low mileage LS 5.3 in it.

[PondSkum]

I have no idea what will make the 4.0 perform... And no intent to do so. It's plenty powerful enough for what I need it to do. But I would like to know what your research results are.

Also, those 1800 views are probably from search engine bots creeping the forum. We only have 1,100 members. You probably only have about 20 solid views.

[TEXAS MUDBUS]

Yea but that just goes to hold true the statement 'it's never a good jeep till it gets a SBC swapped in', which I do agree with. This is for the guys who aren't intereted in swaps.

I thought we got rid of the search bot problem?

I'll just start posting up what I find when I get some time. Check back in a few days.

[texasfrog]

Yea but that just goes to hold true the statement 'it's never a good jeep till it gets a SBC swapped in', which I do agree with. This is for the guys who aren't intereted in swaps.

I'll just start posting up what I find when I get some time. Check back in a few days. on the average I have never seen a inline 6 gas engine get much better than 14 mpg. in a jeep body,Hp yes mileage no.

[UncleSarge58]

OP,
Just My 2 Cents & It Worked Great 4 Me.
(I Have a 96 XJ 2 Dr 4X4 w/ Hi Out 4.0 & AW4 Auto)

All I Needed to Get Extra Performance was: Mallory High Output Coil & 8mm Silicone Plug Wires / Ford MotoSport 4 Hole Injectors & 2.5" Turbo CAT w/ 2" Turbo Muffler & Exhaust Pipe. Plus a Real Cold Air Intake (Thru the Grill).

Throttle Response Is Significantly Better! (Especially from 35mph to 55mph)
At 35 it Takes Off like an Early 70's Small Block V-8! Great Passing Power at 55-65mph Too!
Mileage went from 14 to 16mpg in town & went Up from 17 to 18mpg Highway!
Not Great Mileage Gains. But, The Performance Gains Are Well Worth the Money!

Just Wish I could Afford the Time & Money 4 a Supercharger Set Up!
Now IMHO : That's The Way to Get Real Power Out of the Jeep 4.0 (Easy 300HP & 300 Ft Lbs Torque/ SWEET!)

UncleSarge58