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New engine recommendations

MomoJeep

MomoJeep

Basic User
City
Seattle
State
WA
NEW ENGINE:
I destroyed the 4.0L head on my 258 block with HESCO MOPAR MPI conversion. I want to keep it relatively simple and not too expensive. I care about power, and I also care about gas mileage. I want to keep fuel injection.. Options:

(1) Try to throw a new 4.0L head on my block. This requires plugging water jacket holes (mine started to leak after 50k). To ensure they don't leak could be welded, but then more work is needed, hardened valve seats, etc. (the head will warp and soften). The valve seats are close to the water jacket, so it's risky.

(2) Just throw in a 4.0L. I currently have the OBD1 setup. Would have to change to OBD2 wiring? Would this have more or less power than my old setup: the 4.0L head on the 258 block...?

(3) Do a 4.0L stroker. I feel most fond of this idea because (a) I may be biased because I read about it a few times and thought it was cool. (b) I'm under the impression that it would be fairly direct bolt-in. But just like (2) above, would I need to change wiring, computer, etc?

(4) V8 (a) An LS. I don't just automatically feel the need for a V8. And I want to keep it simple, and prefer not to have to change wiring, cooling, mounts, etc. (Just spent $400 on new radiator and some cooling system upgrades or 258/4.0.). I;m not familiar with LS's and I think I prefer to stick to Jeep engines I know. (b) AMC 304 or 360. If I was to go this route I don't know if they are easily converted to fuel-injection?

I definitely appreciate any Suggestion, thoughts, advice?
 
Oh, I guess another option is finding a 4.0L and reusing my Crank and Pistons to make a stroker. But how Easy?
 
Rebuilding an I6 near what you already have will be the least expensive and quickest option.

If you are swapping, I would pick 4a. LS engines are swapped in everything for good reason. They make great reliable power and are pretty efficient while doing it. Parts are inexpensive and in stock at auto parts stores.

A 304, 360 or 401 are good options for purists. It would be a similar amount of work to install as an LS (if using EFI), but without factory EFI options and overdrive transmissions (without adapting).

That said, there isn't a right or wrong answer on whatever you chose. There are different options because everyone has their own preferences.
 
On my red Scrambler, when I rebuilt it, I kept the stock 258 with Mopar MPI. Never even checked the compression on engine. Drove the piss out of it for 30k miles, multiple cross country trips, eventually got a tick. Ended up being a cracked piston skirt.

Sometimes $hit happens for no reason.

I ended up swapping in a new stock 4.0, reinstalled the Mopar MPI on it, and bolted on all of my 258 front accessories, clutch, starter, etc. Quick, easy, relatively inexpensive in both time and money.

I have drove the same Scrambler, now with a 4.0, cross country numerous times, on the same routes/loads as when it had a 4.2 with MPI. I prefer the stock 4.0, has more usable power at higher RPM's compared to the 4.2. The 4.2 has a hair more torque right off idle versus the 4.0, but I never miss it. The 4.0 with the shorter stroke vs the 4.2 just seems to be a better choice for how I drive, breathes and revs easier/better.

I will NOT ever stroke a 4.0. It can be done, not sure it is worth it for the modest power increases that come with the expense, headaches, and potential reliability/tuning issues.

Think of how many stock 4.0's run reliably for close to 300k miles before they bite the dust. How many strokers have?

If you need more power, plan on towing a trailer regularly on long trips, just swap in a V8. I sold a Scrambler with a new, bone stock TBI 350. It would have been more useful for long trips towing a trailer vs a 6 cylinder. I drove it cross country, too. I just prefer my 6 cylinder powered Jeeps for how I drive.

All just my opinions, based on close to 50,000 miles of driving 4.0/4.2 powered Scramblers with Mopar MPI cross country, and everywhere else. I think I put about 10k on my TBI 350 powered Scrambler, same routes/trips/usage.
 
spankrjs said:
On my red Scrambler, when I rebuilt it, I kept the stock 258 with Mopar MPI. Never even checked the compression on engine. Drove the piss out of it for 30k miles, multiple cross country trips, eventually got a tick. Ended up being a cracked piston skirt.

Sometimes $hit happens for no reason.

I ended up swapping in a new stock 4.0, reinstalled the Mopar MPI on it, and bolted on all of my 258 front accessories, clutch, starter, etc. Quick, easy, relatively inexpensive in both time and money.

I have drove the same Scrambler, now with a 4.0, cross country numerous times, on the same routes/loads as when it had a 4.2 with MPI. I prefer the stock 4.0, has more usable power at higher RPM's compared to the 4.2. The 4.2 has a hair more torque right off idle versus the 4.0, but I never miss it. The 4.0 with the shorter stroke vs the 4.2 just seems to be a better choice for how I drive, breathes and revs easier/better.

I will NOT ever stroke a 4.0. It can be done, not sure it is worth it for the modest power increases that come with the expense, headaches, and potential reliability/tuning issues.

Think of how many stock 4.0's run reliably for close to 300k miles before they bite the dust. How many strokers have?

If you need more power, plan on towing a trailer regularly on long trips, just swap in a V8. I sold a Scrambler with a new, bone stock TBI 350. It would have been more useful for long trips towing a trailer vs a 6 cylinder. I drove it cross country, too. I just prefer my 6 cylinder powered Jeeps for how I drive.

All just my opinions, based on close to 50,000 miles of driving 4.0/4.2 powered Scramblers with Mopar MPI cross country, and everywhere else. I think I put about 10k on my TBI 350 powered Scrambler, same routes/trips/usage.
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I agree there's a lot to be said for NOT modifying an engine! When you say "Think of how many stock 4.0's run reliably for close to 300k miles before they bite the dust. [[[How many strokers have?]]] - Good question, I really have no idea. I have no experience with a stroker. Do they not last as long? Are they best for rock crawlers?
 
This old thread just reminded me of something.. https://www.cj-8.com/threads/4-0-hype-they-dont-make-em-like-they-used-to.36042/

back in the day I thought the 4.0L head conversion for the 258 was pretty cool. In retrospect, I *think* the real gains come from the MPI kit, not the head swap (Do ya'll agree with this?)... Also, the plugged water jackets were just starting to leak a little...

SO ---> The old thread above states that a 4.0L head gets you 20-40hp more. But some work on the 258 block and head can get a lot more than that. What if I just went back to a 258 head (maybe with some basic performance mods). Will the MPI bolt up the same to the 258 head as the 4.0 head?
 
With a heavily loaded Jeep, towing a boat, in mountains ... I would drop a V8 in and not look back. Easiest would be a chevy 350 with a throttle body EFI like a sniper or ezEFI system. The next step would be an LS converted to 3 wire hookup.

Easiest would be a reman 258, reinstall the EFI and don’t expect a heavily loaded Jeep to keep up with modern trucks on the road.

Strokers are great, but you won‘t get the longevity out of one like an OEM setup. Just go over to jeepstrokers.com to learn more and see what issue stroking the 4.0 creates. It is on my list of “todo” builds, but not for a daily driven vehicle.

There is a reason I am going the LS swap route for my build where I plan to run a full hard top and end up with a heavier than average Jeep. Also, the LS can be modified easily to have insane power. You will never get similar power out of the 4.0 or 4.2.

In the end, if I were in your shoes, I’d just get a reman 4.0 long block, swap it in and keep going. (With a paper filter
 
sdsupilot said:
A 304, 360 or 401 are good options for purists. It would be a similar amount of work to install as an LS (if using EFI), but without factory EFI options and overdrive transmissions (without adapting).
Click to expand...
A 304, 360 or 401 are good options for purists. (y)
 
Anyone got a 258 head to get rid of? Or know where to find a good "built" one?

The more I think about it, at this time I'd rather spend my money on other mods and drop a 4.0 or V8 in further down the road. The rebuilt 258 (0.030" over) short block only has 50k on it. If it's still in great shape, how about a drop a good 258 head on it, and reconnect to my existing MPI!?

The question is, where to get a 258 head and what to do to it...
 
Can your 4.0 head be rebuilt? Hard to believe the head is destroyed unless it is warped or cracked.

You can always drop this on, but at that price you could get other things too ... Edelbrock 4.0 Head
 
Randyzzz said:
I’m late to the party. If you really want power- an LS is the hot ticket. But...I guarantee you a 4.0 or 258 will be a lot easier.
Click to expand...

Yes, this is clear to me now. I think down the road, bringing in an LS is what I'd do if I want to keep driving it long-term. For now, just a new head seems to be most straightforward. Even swapping in a 4.0L would be more costly and more work than slapping on a new head, I think!?
 
Before spending money, I’d figure out what failed and why.

If it was caused by dirt ingestion, then the rings may be toast. Then if enough dirt got by the rings, bearing could be scored. Then throwing a new head on a trash bottom end would be a waste of money.

If it was caused by an improperly timed cam shaft, throwing a new head on there is just wasted money unless the cam timing is set properly.
 
ag4ever said:
Before spending money, I’d figure out what failed and why.

If it was caused by dirt ingestion, then the rings may be toast. Then if enough dirt got by the rings, bearing could be scored. Then throwing a new head on a trash bottom end would be a waste of money.

If it was caused by an improperly timed cam shaft, throwing a new head on there is just wasted money unless the cam timing is set properly.
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Are the K&N filters that came with the Mopar MPI conversion kit really that bad? (I had not heard of dirt ingestion before with these conversions...).
 
Here's a pic. All the cylinders follow this same pattern. The exhaust (Smaller) valve seat has recessed so far that there is only "one angle"! The three angles usually present have been hammered away!

What does this indicate?
 

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Was this motor built with a 3-angle valve job? I don't think 3-angles are really as prevalent as people may think... What was the compression on each cylinder? If the valve seals and holds compression, I'd say the head is NOT ruined. But I missed the preface to this story...
 
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