2003 4.0 I6 engine rebuild

Zack Magnusson

Zack Magnusson

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Joined
Nov 17, 2016
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27
Location
Limestone County, AL, United States
My jeep is a 2003 Rubicon. The engine is burning 2 quarts of oil per week when I drive it to work. I have performed a differential compression test and confirmed that there's major blow-by on the rings in the #3 cylinder.

I've really not found a crate motor that I have high confidence in. ATK seems to be the only game in town (also what NAPA carries last time I checked) and good reviews of them are hard to find. The local Jasper Engines guys want $4-5k to swap it if the engine is available (which, last time I checked, it was not).

So I am proceeding down the route of doing it myself. I'm no expert, but I've built several engines in the past, including the straight 6 in my old CJ-7.

1. Before I proceed down this path, does anyone know of a good crate engine supplier with a good reputation?

2. I am also considering stroking the engine while I'm in there. Anyone done it? These guys seem to have really nice kits: http://www.cleggengine.com/performance-engine-rebuild-kits/stroker-kits/jeep-4-0-stroker-kits.html.

I'm also considering this sweet header and pipe from aFe: https://afepower.com/afe-power-48-48020-yn-twisted-steel-header-connection-pipe-race-series. It's pricey, but I'm highly suspicious that all of my catalytic converters are hosed up with burned oil residue. and replacing the three of them will add up fast. I have a Borla cat-back that I will probably use in conjunction with it.

3. Lastly, anyone had a 4.0 professionally tuned after major upgrades? Please advise.
 
I like the looks off the striker kit but in my opinion if your wanting more power and your in the market for a new motor I would just do a swap to ls or hemi. That’s my plan I have an 06 that is in need of more power. I’m thinking about swapping for the 5.7 hemi.


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Can't help much. I do have a friend running a 4.6L stroker that is pretty nice. That header looks pretty sweet too, but where do your downstream O2 sensors go? Will watch in anticipation of the results!
 
Im likely to do a rebuild soon too. Wondering the same Q as you OP. LS swap would be tits, but I dont even know what the ball park cost of that from start to finish.

Keeping on eye on this thread


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fourpointzero said:
Im likely to do a rebuild soon too. Wondering the same Q as you OP. LS swap would be tits, but I dont even know what the ball park cost of that from start to finish.

Keeping on eye on this thread


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So. I CAN shed some light on that. I have a friend with a J10 running the old 4.2. He wanted to swap in a Vortec 5.3. By the time all the adapters and mounts were in, engine control was done, gages, etc. the shop he had quote it (pretty well respected local guys) hit him with a $13,000 price tag. Needless to say, the ol' J10 is still running the 4.2!
 
I don’t want to cut sheet metal, re-wire, do adaptors, or any of that kind of stuff. That’s why I’m keeping the 4.0. Stroking it while I’m in there anyway is pretty low impact. May want to get it re-tuned though, and if I do that, can just turn off the two downstream O2 sensors if I need to.


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I’m still looking really hard at doing the 5.7 hemi swap should be straight forward and a close swap.


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You might want to consider looking around your area for a local re-builder with a reputation. I did that with my sons TJ and they turned it around in a week.
 
This would be a simple engine to rebuild. I have rebuilt several engines including a couple of Ford straight 6’s. I would do a simple rebuild, stay away from anything from stock . This approach will cost you the least and give you the most predictable results.


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Jakekk1 said:
I’m still looking really hard at doing the 5.7 hemi swap should be straight forward and a close swap.


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If you have really deep pockets, it would be an awesome swap!
 
TJ4Jim said:
You might want to consider looking around your area for a local re-builder with a reputation.
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Good advice for the OP, Jim. That’s likely the rout I’ll be taking. There is a reputable machine shop that’s done plenty I6’s in my area. The quote was $2500 out the door w new hoses and 1 year warranty.


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Jakekk1 said:
You really think that it would be that costly?


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Well, Hemi engines go for a premium on the used market. Not to mention all the other stuff you'd need. I know for a fact you'd spend probably $5000 or more just on the parts, and if you paid to have someone do it for you, you'd spend upwards of $8000.

I know a guy here locally who swapped a 5.2 into his LJ Rubicon (that's the V8 from the Dodge Durango) and once all was said and done, it cost him 8k to have a shop do it for him. Things add up very quickly, that's for sure.

I'm not trying to be discouraging though, I think it's an awesome swap! I just know that it costs a lot of money.
 
Chris said:
Well, Hemi engines go for a premium on the used market. Not to mention all the other stuff you'd need. I know for a fact you'd spend probably $5000 or more just on the parts, and if you paid to have someone do it for you, you'd spend upwards of $8000.

I know a guy here locally who swapped a 5.2 into his LJ Rubicon (that's the V8 from the Dodge Durango) and once all was said and done, it cost him 8k to have a shop do it for him. Things add up very quickly, that's for sure.

I'm not trying to be discouraging though, I think it's an awesome swap! I just know that it costs a lot of money.
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I didn’t really think about it that way thank you for the insight.


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I lost the engine in my YJ, and found an early 90's S10 with a fuel injected 4.3 vortec and a bad 4l60-e trans. I am not sure how much you can do yourself, but I paid 1000 for the non running s10 and yanked the motor and trans and computer. I Ordered an advanced adapter motor mount kit, maybe 100 bucks. I emptied the trans to line everything up. If I remember right my Jeep transfer case bolted right on to the back of the 4l60-e. I may have had to have changed the output shaft but I don't think so. I rebuilt the trans and installed it all into my YJ. I ordered a "Painless wiring kit" for the engine and trans. I had to install an electric fuel pump, so I went to a wrecking yard and bought a gas tank out of a new YJ and installed it. It bolted right in no mods necessary. All in all with all of the parts it cost 2K done. But I was able to do all of the work myself. It was a lot of work and wasn't my main transportation so it was fun. One issue I had was trying to get it to pass emissions. I mean the 4.3 would pass every time, but then sometimes you would get some jackhat that would say Hey that is a chevy motor and fail me based on a visual. So I would go to another emissions place, and as long as it passed at the tail pipe, they would let it through. So it was always a concern and a worry. That is why I won't do that now to my TJ, but if I didn't have to worry about emissions, I would definitely drop a small V8 in it.

Oh and FYI, I sold the S10 body with no motor or trans for 500 bucks, so it only cost me 500 bucks for the drivetrain.

The moral of the story is the more you can do yourself the cheaper it is.
 
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fourpointzero said:
Good advice for the OP, Jim. That’s likely the rout I’ll be taking. There is a reputable machine shop that’s done plenty I6’s in my area. The quote was $2500 out the door w new hoses and 1 year warranty.


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Eddies Valve Grinding in South Amboy did our re-build.
 
fourpointzero said:
They’re right up the road from me. So you’d highly recommend them? Also, I see you left the great shit state of NJ- good for you!


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The were great during the rebuild, even called me to the back shop to show me what was going on with the rebuild. They also did the head on my TR6.

And Yes, finally got out of Dodge in 16'
 
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Just for fun I found a picture of my vortec swap. Please excuse the wiring mess I was just a youngster.

PICT0026.JPG
 
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