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jrwhit04 01-03-2012 10:01 AM

2003 4.7L Engine Decision
So, I purchased my first WJ from my brother, it's a 2003 Limited with the 4.7L V8 and the Quadra-Tac 4x4 system. When I bought it, I KNEW it had a blown head gasket, so I was well aware that repair was necessary, and it was why I got it for so cheap in the first place.

This weekend I finally dug into the beast, and sure enough, the head gasket was blown but I also found cylinder's 7 and 8 were scuffed. They were "lightly" scuffed, but no matter how hard I try, I just can't ignore the fact that they are indeed scuffed.

This brings me to my question, and that is where do I go from here? As I see if I have several options:

1. Rebuild the engine I have (assuming block and heads are not cracked)
2. Get a junk yard engine that's running with low miles
3. New engine, or newly rebuilt engine

Also, I would "like" to have the HO engine, and based on threads I read, it is possible, and not that difficult. I am looking for any advise, or recommendations on which option, AND if the HO conversion is worth it in the long run. Thanks in advanced.

- Robbie

Me Fix 01-03-2012 02:04 PM

Re: 2003 4.7L Engine Decession
Why do you want the HO engine? Lots to think about here!

Two bad cylinders suggests a complete rebuild. It can be very hard on other parts after fixing up two cylinders. It's like doing a valve job and then having renewed pressure on all the main bearings and piston rings. I always found it better to just rebuild the whole thing. Once you get things apart, you can take the major parts to a machine shop. They will check everything, straighten up the cylinder walls, polish the crank journals, set you up with new rings, do a complete valve job with new seals. All you would have to do is clean up all the other parts and brackets and put it all back together, if you are that kind of guy. We got 350,000 out of an old astro mini van before I rebuilt the engine ansd had the transmittion serviced. We then got another 100,000 or so before we traded for a new one. That ended up being a mistake, because the new one become a nightmare. One of those, "I'll never have another one of those" vans.

Your looking at least a different ECM and program with the HO engine.

jrwhit04 01-03-2012 02:20 PM

Re: 2003 4.7L Engine Decession
I want the HO simply because it's "cooler".........sounds kinda dumb when I say it like that, but honestly, I can't come up with a better answer. Simply more power and torque, which I generally like!

So your vote is rebuild...... interesting, my buddies are saying the same thing....

I have looked at and see the differences in the HO and non-HO. The one thing that isn't clear to me is if it is possible to mount the knock sensors to my non-HO block. Assuming I got the HO crank, HO rebuild kit, complete HO cylinder heads and intake, could I make my non-HO an HO or is there a difference in the actual engine block that would prevent this?

Thanks again for the advise, I will post which direction I end up going in.....

JeepNut 01-03-2012 03:37 PM

Re: 2003 4.7L Engine Decession
How about since you should rebuild and thinking of a HO why not do your block .....go a stroker kit a port and polish HO cams and a late manifold. Now that cool! Money permitting of cousre

wjgiants39 01-03-2012 04:10 PM

Re: 2003 4.7L Engine Decession
I would rebuild the one you got and get H.O. cams and a newer 4.7 intake manifold and go from there with whatever else you feel needed, might as well work with what you got

Martyp 01-04-2012 06:21 AM

Re: 2003 4.7L Engine Decession
I'd say rebuild what you have and it would be the perfect time to install some HO cams or a regrind with new springs etc, 08 intake manifold + TB converter and get your TB ported (or buy a ported one) then install a 180 t-stat. Then get a SCT tuner and custom tune for it.

If you have enough to sink into it, you could bore it out a little, new pistons or fit a stall converter etc. etc.

Have a look on and/or PM him on here. He is really helpful and is one of the main places to get 4.7 goodies. :thumbsup:

jrwhit04 01-04-2012 08:17 AM

Re: 2003 4.7L Engine Decession
Sweet website, thanks Marty for the recommendation. It would appear that a rebuild is pretty much the consensus, both from this forum and pretty much everyone I talk to. Now I have to figure out what I can afford as far as a rebuild goes.

I do have another question, and that is about the crank. From what I gather, my NON-HO engine doesn't have a forged crank, and an HO does. Is it worth getting the forged crank if I am planning mild upgrades, like you mentioned above?

Thanks again for all the advise, I am new to the 4.7L world, so this is a learning experience for me for sure. If this Jeep was the standard 4.0L inline 6, I would be much more in my comfort zone!

- Robbie

Martyp 01-04-2012 08:42 AM

Re: 2003 4.7L Engine Decession
Sorry but you can't get the forged crank anymore... Airram listed on their site last time I looked but Mopar now just offer one crank. Whether you get a forged or non-forged is a lucky dip I think.

To be honest though, I don't think its all that important unless you are going to add a lot of boost or NoS to the motor.

Getting the ARP stud kits for the motor would be a good idea though. Although if you speak to Nick @airram he'll tell you what you'd need to keep it safe.

Me Fix 01-04-2012 10:44 AM

Re: 2003 4.7L Engine Decession
What about going to the junk yard and maybe finding an WJ with and HO engine. If you were lucky, you might be able to get everything needed to simply replace what you have now. Or if you can find an HO engine and related parts, you could do a rebuild on that before you install it. Either way you go, you're going to be spending some bucks. Don't take this wrong, but is your Jeep worth it? It is possible to spend more than your ride will be worth after you get done!

jrwhit04 01-04-2012 01:06 PM

Re: 2003 4.7L Engine Decession
Ha! My thoughts this worth it?

Here's what I have come up with, the Jeep is in great shape cosmetically, I got it for hardly anything, so even with investing $2000 or $3000 in an engine, I will have less in it than it books for (but damn close). I plan on driving the wheels off this thing, so yeah, it's worth it to do it right so I don't have to do this again.

I have been doing some looking around and I have a lead on a running HO engine with 74k on it. They want $2100, and will work in a 3 year warranty for $200 extra.

Due to the fact that I am having trouble finding someone with HO cam's in stock, and as Marty informed me, I can't get a forged crank........I am leaning towards getting this HO engine and "freshening" it up a bit with new gaskets, possibly new timing chains/tensioners, and a new oil pump and calling it good.

Thanks to everyone for their thoughts and advise, it is most appreciated.

- Robbie

cheapjeep 01-04-2012 02:25 PM

Re: 2003 4.7L Engine Decession
In the interest of keeping you from getting in way over your head there are some serious points to consider.
1.The most important.Since your GC is an '03 you are in the "grey" area concerning engine management systems. It could be jtech or ngc. If you don't have the jtech system forget the HO unless you feel like gutting most of your vehicles original wiring harness and are a Mopar wiring guru. Jtech has the separate tcm mounted by the overflow bottle. If you dont have this its ngc.

2.If you read jeepwelds stickie you'll see he still had considerable obstacles to overcome even going 4.7 jtech to 4.7 jtech.This could possibly be to the fact that he was putting an HO into a GC that was built before this engine was around or maybe not.They may have made provisions in the later harnesses for both or possibly not. If not you have quite a few sensors issues ahead.
3.If you use your ecm that came with your Jeep you will need a custom tune and a tuner that supports them.If you use the Ho ecm your gonna have it towed to the dealer to have it programed for your key because it won't run for more than 4 seconds.
4. I'm not trying to discourage anybody,I'm all for performance,but it's good to know what you're getting into beforehand.

jrwhit04 01-04-2012 02:47 PM

Re: 2003 4.7L Engine Decession
Thanks for the detailed response, it is much appreciated. I am especially glad you sent the picture, because I had read about the JTEC, non-JTEC issue on this board and many others, and based on what I was reading I "thought" I had a JTEC vehicle. Since my jeep has what you showed in the picture, this further confirms what you said about it being JTEC.
I might be optimistic, nieve, stubborn, or some combination there of, but I am "hoping" that the sensor issues encountered by jeepweld won't be as much of an issue for me since my vehicle was made when the HO was available as an option. Also, if I do encounter the issues, luckily I can learn from his experience and at least know which direction to head in trouble shooting. This might be silly, but it's a risk I just might be willing to take.

And about getting in over my head.....I'm a mechanical engineer by trade, so even if I get myself in over my head, I probably won't admit it! :)

Also, my daily drive is a 1984 Chevy truck with a Cummins engine out of a 1989 Dodge and a NV4500 transmission from a 1998 Chevy truck. While I might be new to the 4.7L world, I am familiar with engine swaps, and running engines in vehicles that the factory didn't put them in.

I am sure there will be PLENTY of unforeseen obstacles if I decide to go the HO conversion route, but the more I think about it, the more I think I might just have to do it..... :)

Thanks again for all the help, it really is appreciated.

- Robbie

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