engine and drivetrain upgrade 81 SX4

[Cole1986]

I'm wanting to make my SX4 my family skiing car. It has the iron duke in it so i need something with a little more power and economy to make it up the mountain. After reading a ton of forums I want to drop a 4.0 fuel injected engine in it, with an auto trans, and a 2wd 4wd 4wd low transfer case. The question i have is; if i buy a jeep and pull everything from it would it work for what i need. I'm looking to start this project this summer and would love to have some input on the matter.

[greymarooneightytwo]

Alright, so... I think '87 and up XJ's and Wranglers had the NP231 and some '87 and up Wranglers had the NP242, both would likely work fine for you, and I think both had the 4.0l i6, also introduced in the '87 model year... 

That being said, you'd be better off with a post-'96 but pre-2k 4.0l, as they had better blocks and the RENIX system had long since been replaced by a more robust (and more standard) engine management system.

Chrysler also enlarged the throttle body and redesigned the intake and exhaust manifolds for more efficiency, and the fuel injectors were replaced with higher flow units. Camshaft timing was also changed. Overall result: 190HP.

After '99 the 4.0 was redesigned for emissions, resulting in a weaker block and coil on plug distributor-less system.

Crap crap crap.

I was considering a similar plan, but I'm pondering a Ford 4.9 straight six and running gear now, because of parts availability and cost to replace things when they break... I'm hoping to find a dead SX/4 to swap my current 4.2l into

[Amc1320]

Or,

Iron dukes can also be made to make a lot more power, there is a member in here who just did a build up and reinstalled one and they are reporting that it made a huge difference

Those iron dukes were used in a Lot of ski boats too

Just a thought

[BenM]

The main things you'll have to figure out are the front accessories, the transmission cross member, and the rear drive shaft.

There's plenty of range in the front drive shaft, but if you get the AW4 it will move things around just a little, and most Jeeps used a slip yoke on the rear drive shaft.

Some Jeeps have offset fans or other oddities in the front, and used different A/C pumps and P/S pumps, so you may have to improvise a little.

You'll also need the 6cyl engine cross member for an Eagle.

I'd prefer the a case like the 242 or 249 for a snow vehicle. The full-time option allows front-rear differences in snow which reduces the chances of under steer.

[Cole1986]

thanks for the feed back. I"m no mechanic so i'm sure all have more questions as this project continues.

[Cole1986]

k so what if i kept my manual tranny, what options do i have as far as transfer cases? and will the 4.0 bolt up to it?

[eaglefreek]

You say you're "no mechanic". While many of us here aren't either, if you have almost no mechanical skills it will be tough, but it's still doable with patience and perseverance and money. Is it a 4 or 5 speed? Your transmission will not bolt up to any AMC engine, including the 4.0L. The Iron Duke has a standard Chevy 90 degree bellhousing pattern. If you have a 4 speed, most likely an SR4, if a 5 speed, it would be a T5. Neither or very desirable as far as reliability behind anything with a little power. I have no experience with doing it, but you should be able to bolt a Chevy 3.8L/4.3l V6 or a Chevy V8 with the 90 degree bolt pattern to your transmission. To get 4 Low you could install a NP229 or NP242 to your stock transmission, but they will both need a little work to bolt up. I've always wanted to get a small body AMC and bolt a more modern 4cyl. Like a Quad 4 or Duratec engine in it. Here is a company that will allow you to mount a Quad 4 to your transmission. http://quad4rods.com/index.php?page=shop.browse&category_id=1&option=com_virtuemart&Itemid=100041

[Cole1986]

thanks eaglefreek, with that said i'll probably replace the tranny. I would really like to put a i6 due to the fact that the hills up to the resort are no easy climb. It was mentioned that i would have to change the cross member; is that something i would have to modify myself or can i part something? by the way i love this site.

[mudkicker715]

Amc used 2 different xmembers. one for manual one for auto. there is a different spot for both that all have spots for so........ do the math i guess

[eaglefreek]

Amc used 2 different xmembers. one for manual one for auto. there is a different spot for both that all have spots for so........ do the math i guess

I believe he is talking about the engine cross member, which I understand would need to be changed out with one from a 6 cyl. car. If you go that route Cole, a 4.0L will bolt in. Add an AX15 5 speed and a 242 transmission and you'll be set. You should already have 3.54 gears in the differentials which will be perfect with that engine transmission combo.

[Cole1986]

awesome, can't wait to get started

[mudkicker715]

Amc used 2 different xmembers. one for manual one for auto. there is a different spot for both that all have spots for so........ do the math i guess

I believe he is talking about the engine cross member, which I understand would need to be changed out with one from a 6 cyl. car. If you go that route Cole, a 4.0L will bolt in. Add an AX15 5 speed and a 242 transmission and you'll be set. You should already have 3.54 gears in the differentials which will be perfect with that engine transmission combo.

true enough understood. however that movement gives you an ability for different combos. as far as the motor xmember i changed mine to accomidate a amc v8. without looking i do not remember how i moved mine it was easy for me to repossition and move it fore or aft. again i forget how i did it. i can say some welding was involved. but it was also bolted iirc.

[Baskinator]

As a fellow "non-mechanic" Eagle SX/4 enthusiast, this is the best plan of action I can suggest.

First of all, you should look for an Eagle wagon parts car with 4.2 I6 and A998 auto transmission. Shouldn't be entirely difficult to find one rotted out at scrap price, and these are the most common configurations 

This will give you the engine, transmission, and crossmembers for your build, as well as a plethora of other parts that may likely become worn on your Eagle. Best to rebuild them before installing for good measure and reliability. I would highly recommend an NP242 transfer case as this can be made to work on an Eagle relatively easily, and it is probably the most versatile of the New Venture/New Process t-cases. You may also be able to adapt a Grand Wagoneer shifter, as the Eagles all came with an unused, dedicated mounting spot.

You should definitely start out with the 4.2 engine. It will take no true modifications to install, and everything can come from the parts car. Once you get this in you can start thinking about more power/mileage, because the 4.0 is a whole different can of worms.

The 4.2 can later be fitted with a 4.0 cylinder head, preferably the 7120 casting from '93-'96 I believe. You use the stock intake and a 4.0 header, which requires exhaust mods and a grinder to fit in the crowded Eagle engine bay and wrap around the front driveshaft.

Once you have all of that running well and you need more power, better mileage, and truly reliable starting, you can finally start looking into fuel injection. Your options are to use the parts from a Jeep, including intake, fuel rails, full wiring harness, flexplate, starter, etc. (yes, you need the flexplate and starter because of the crank position sensor, which requires bellhousing mods) and buy an electric fuel pump and block off plate for the old pump OR shell out $1200 to $2500 for an aftermarket system which will be easier to install.

Other helpful additions could include, but are not limited to: Motorcraft ignition upgrade (very simple), HEI distributor, MSD 6AL ignition box, aluminum valve cover, limited slip rear differential, Dana 44 from a Comanche (certain year is the same width)...

Dana 44 isn't totally necessary, especially with only a 4.2, but would be significantly stronger than the stock axles and your wheels won't fall off if they break. A limited slip would be a good addition for snow driving, and should be pretty easy finding gears for considering you have a 4 cyl. The 4 cyl Eagles came with 3.54 front gears, which are prized for torque and severely limited availability. Of course, you should confirm that's what it has before blindly installing gears.

These kinds of ambitious mods don't take an expert mechanic to accomplish, but they are certainly no single weekend task. I would estimate this to take 1-2 years for a busy working person with a family, but less if you have a nice garage and keep at it. I'm not trying to discourage you, however you should know what you're getting into before tackling an Eagle project. It will be AWESOME when it's all done

[Baskinator]

By the way, the T5 is a good transmission if you want to keep it manual. Others have talked about AX15, NV3550, NSG370, and more swaps, but I don't have any info on that. You'll want to look into other clutch slave cylinders, as the stock parts weren't too great. Avoid the SR4 at all costs, the shifters are very prone to breaking and not easily found intact. You will surely get much better gas mileage with a manual, which is imperative in an Eagle. 

I'm not much of a manual guy (yet).

[mudkicker715]

Everyone will knock an sr4 trans. i threw one behind my stroker sedann i can go sideways with no problems. its how you shiftvthat is the problem. i can for example shift without clutch. i however beet the snot out of the joystick offroad. maybe i am the perfectmatch to a sr4.