2 Cool Fishing Forum banner

1 - 20 of 29 Posts

·
Banned
Joined
·
9,560 Posts
Discussion Starter #1
How dificult, on a scale of 1 to 10, would it be to rebuild a '94 Jeep 4.0L I6? I'm considering purchasing the parts to stroke the motor. There is a 4.7L stroker kit for the 4.0L motor I can get for around $1k, and have one heck of a motor when I'm done. I'm fairly handy with tools, but I've never rebuilt a motor. In the last two weeks I've done smaller things like replacing rotors and pads, changing spark plugs, checking compression, changing fuel filter, draining/flushing (via the aux cooler return) tranny fluid and replacing filter, drain and fill differentials, drain and fill transfer case, changing oil, replacing throttle body with 62mm bore TB, etc. I plan on installing a lift and replacing shocks next weekend. I've done all of this by myself. I guess what I'm asking is, do you have to be somewhat handy with tools and know how to read and follow directions (which I can handle), or do you need to have in-depth knowledge of the inner workings of a motor (i.e. be a mechanic, which I'm not! ;) )? I have a basic understanding of how a motor works, but I've never torn one down before. What do y'all think? I know it'll take me a couple weeks to complete, and there are several things that will have to be done at a machine shop (boring cylinders, etc.).
 

·
Premium Member
Joined
·
40,480 Posts
It's not hard

if you have the tools. I have rebuilt many motors and each one is different, some just give in and everything is smooth, others fight you all the way. Just take your time and no short cuts. Make a plan sheet and collect all the parts and tools first and be flexable as you will (maybe) find items you want or need during the build.
If possible, get the motor blueprinted, honed and decked and then do your build. Just keep everything clean. Always ask for help on the first one, maybe try and find a jeep club close to you, their experience would be priceless.
 

·
Banned
Joined
·
9,560 Posts
Discussion Starter #4
The crate short block 4.7L stroker is around $3k+. Not an option for me. I barely paid that much for the whole Jeep! ;) My max is around $1500 for this project.
 

·
Starboard List
Joined
·
1,882 Posts
Shady i think you can do it. All you'll need is a manual and take your time. Make sure you torque everything right and try not to rush and forget stuff. The hardest part is not having all the required tools. Often times you can "borrow" tools from autozone. Check on these two sites. I'm sure you can find a "how too" in web format that somone has done allready.
http://www.pirate4x4.com/
http://www.jeepsunlimited.com/forums/
Later, Hop
 

·
# 314
Joined
·
524 Posts
Shad,I can send you a bunch of links to Jeep forums if you want.There are some really knowledgable folks on them that can answer any questions you might have.
 

·
Banned
Joined
·
9,560 Posts
Discussion Starter #8
Any info would be appreciated! I'm already on a few Jeep forums:

jeepforum.com
jeepsunlimited.com
nagca.com
autoforums.com

Any others would be greatly appreciated!

Channelcat - Compression on this 4.0L should be 120PSI - 150PSI, with max deviation of 30PSI. My results are:

#1 115
#2 115
#3 130
#4 130
#5 130
#6 130

So, I have two cylinders below allowable PSI range, but my deviation between cylinders is OK.

I've been looking into re-gearing to 4.56 (currently at 3.55), and in fact may be buying a couple ring and pinion sets today. Those'll be a beach to put in, I'm sure! ;) I may be dropping the $500 or so to have those professionally installed...haven't decided yet. Anyway, that's more of a Band-Aid to the real problem, though. Before too long, I'll need to rebuild this motor. I'd like to rebuild it with this Stroker kit, and gain 90hp or so. Just not sure how difficult it would be.
 

·
That DamnYankee!!
Joined
·
4,077 Posts
Check with the company supplying the kit on machine work. A stroker crank & longer connecting rods usually require additional clearance work at the bottom of the bore and sometimes the pan rails.

Also check with them for any head work that might be needed to supply the extra air & fuel needed. I'd try to leave room in the budget for a header if not a whole exhaust. The extra cubes(about 50 of 'em) will be useless if ya can't get enough air & fuel into and out of the cylinders.

A good Chiltons type manual will show you every step of the removal, build & install of the motor. It will also tell you any special tools required. There are probably a few gear pullers required that you won't own but can rent/borrow from Manny, Moe & Jack. Some fluid lines will probably require a special tool to remove in addition to the balancer & possibly the P/S pump.

Between the extra cubes, bigger TB and taller gears PLAN ON needing computer work too.

Later,

Jeff
 

·
Registered
Joined
·
10,847 Posts
Hey Shadman,
Did you find D.B. Sweeny or stake a claim to a silver mine up there?
 

·
Registered
Joined
·
798 Posts
Looking at your compression numbers, the adjoining cylinders raise an eye brow. The rest look very good. IMHO, look at head gasket.
I'm not trying to talk you out of the stroker, just approaching it as if I were doing the project.
 

·
richg99
Joined
·
6,882 Posts
If I were doing that, or any other tear down and put back together job...I'd beg, borrow a digital or regular camera and take a zillion pix of the engine from every possible angle. Then I'd keep the camera handy as I tore everything down. It would help you when it comes time to put it back together. RichG
 

·
That DamnYankee!!
Joined
·
4,077 Posts
ShadMan said:
I've been looking into re-gearing to 4.56 (currently at 3.55), and in fact may be buying a couple ring and pinion sets today. Those'll be a beach to put in, I'm sure! ;) I may be dropping the $500 or so to have those professionally installed...haven't decided yet.
Dude,
If your concerned about your ability to rebuild a motor then you'll be in WAY over your head trying to set-up rear ends. That is one gig I always leave to the pros. You'll need more specialty tools to do the gears then you'll need to do the motor.

ShadMan said:
Anyway, that's more of a Band-Aid to the real problem, though.
If you're gonna raise the truck & run bigger tires gears are a must, not a band-aid, especially on a 'puter controlled rig. I'd do the gears before doing any 'puter tuning or you'll be doing the tuning twice.
Check with 4 wheel parts wholesalers, they usually have pretty good package deals on R&P's with a limited slip or locker installed. You can also purchase a 3 year/36,000 mile parts & labor warranty for about $300.

I'll post up some 4X links later.

Later,

Jeff
 

·
Registered
Joined
·
113 Posts
Shadman,I am old street racer and I pit for a friend at the local drag strip.So I know enough that I can get myself in trouble without any help. LOL A fresh motor is great,but if you are not getting the horsepower to the wheels you are just wasting your time.Proper gear ratio can make a world of difference.If your motor is running fine and is not tapping, burning oil and over heating.Then I would spend the money on the drive train.Then the motor.A motor that is producing lots of horse power and not the proper drive train will not keep up with a motor that has less horsepower and the right drive train.Again the horsepower is not getting to the wheels. Good luck Rusty
 

·
Starboard List
Joined
·
1,882 Posts
Those numbers could come up some if you do a wet compression test. I'd look at the heads/valves and maybe the rings. How many miles are on the motor? You might be able to get more compression after a decarb of the motor. You might have some carbon build up in and around the valve seats. Sea foam works wonders for cleaning up carbon. Ol' timers used AT fluid to get the same results.
 

·
Banned
Joined
·
9,560 Posts
Discussion Starter #16
The motor is not producing much in the way of HP, but has no leaks whatsoever. 160k miles on it, but it runs great, just underpowered. For example, even if you powerbrake it, it can't spin the factory tires in 2HI.

You're right, Jeff. I'll have to go gears at some point, because I do plan on putting larger tires on. The Dana 30 and Dana 35 axles on this thing will have to go before I get too much larger, though. Just not sure in what order to do everything!

So, basically what I've gathered here is that the rebuild isn't overly difficult if you take your time and can get hold of a few special tools (shouldn't be a problem). Plan for extra cost after the rebuild to get it running right (I figured on an extra $500 or so since it'll still be the same motor, just increased displacement, etc.). And let someone else go through the agony that the gear swap entails? With the underpowering I've mentioned here, do you think 4.11s would be sufficient (I have 3.55s now), or just go ahead with 4.56s in case I want larger tires later? This will still be a daily driver, so I don't want to go too high, but too low might be worse! Also, what kind of cost can I plan on to swap the gears out? The downtime would defintely be less going gears instead of rebuild!
 

·
Registered
Joined
·
1,643 Posts
Shad, your real problem is that you are in Colorado. If you bring that jeep back to Galveston co, it would pick up around 35% to 40% more HP. Colorado air is so thin that engines don't preform up there like they do down here.
Even the extra cubes of a stroker kit, won't help that much, unless you can get more air into the cylinders. I don't know if there is a turbo system that is compatible with your engine and computer, but I would check into that first. If there ain't a turbo kit, then see about a supercharger, Getting more fuel in the engine is easy, but at 5000+ ft altitude, getting enough air in the engine to burn it, can be a real problem. Especially when you are used to sea level.
When I lived in Lakewood(suburb of Denver) they told me that a engine going from sea level to 5000 ft, lost 38% of it HP.
If it was me, before I spent a lot on the engine, I would go for some lower gears. Even if you don't change tires. If you go to very much taller tires, then get as low a gear set as they make.
Setting up the gear set in a differential, is much more demanding than rebuilding a engine. No job for amateurs at all.
Also I would check to see what was causing the low compression before I tore into the engine. A dry compression test followed by wet compression test, will tell you what kind of shape your cylinder walls/piston rings are in. If the pressure rises dramatically on the wet test, then you need cylinder wall/piston ring work. If it doesn't rise that much on the wet test, then your low compression problem is caused by something else (like maybe valves/head gasket/ etc).
The wet compression test is done by putting a small (5 cc)amount of 30w oil in the cylinder before running the test. The oil will make the rings seal better, so the pressure will be a little higher, but not over 10% higher unless there are problems. Wait a couple minutes after putting the oil in the cylinder before turning over the engine.
BTW: To get the oil into the cylinder for the wet test, you pour it in through the spark plug hole.
 

·
Starboard List
Joined
·
1,882 Posts
Shady, Is the motor in there fuel injected and controlled with a CPU? If that's the case you may have to have bigger injectors and the computer remapped for more timing and fuel to get it to run right with the stroker. I'm not sure if they sell after market computers for your setup. If they don't you might be able to have your stocker remapped.
--Hop
 

·
Banned
Joined
·
9,560 Posts
Discussion Starter #20
Well, I gues the first thing I need to do is let her breathe a little easier. A K&N FIPK should help, along with a little exhaust work. I hadn't really thought about the altitude being the problem, since I drive a turbo-diesel. I've noticed a bit of throttle lag since moving up here, but when the turbo spools up, it flies. Her Jeep doesn't ever feel like it has much power. I guess that could be due to the thinner air. Well, let's try a FIPK then, some exhaust work, then gears. I can do all that for the $1500 I planned on spending for the engine rebuild.

BTW, how much effect would an exhaust manifold leak have on performance? I do have a manifold leak (like nearly every Jeep Grand Cherokee in this body style!). I can hear the "tapping" sound that grows faster with acceleration. This body style has a history of exhaust manifold problems. Anyone know where I can get some aftermarket headers cheap?

Hop - Yes, it has EFI. Not sure how the people who have gone the Stroker route have programmed the computer. I know that many of them use Ford Mustang injectors, and I figured that $200 into the $1k cost I had mentioned. I don't know what computer mods they have made, if any, so I'd have to check it out.

Here's a guy who wrote up an article on his Stroker project. I was basing my project on his:

http://www.jeep4.0performance.4mg.com/stroker.html
 
1 - 20 of 29 Posts
Top