Eagle Race Car! 81 SX4 Project

[eaglefreek]

Most likely a TF998 transmission.  NP129 unless someone swapped it. You wouldn't notice the difference between the 129 and 128 on pavement. Dana 30 up front, AMC15 rear. You don't have much of an option up front. You don't want a solid axle in the front for racing. Your rear's weak point is the two piece axles. You can go with a Chrysler 8.25 out of a Jeep Cherokee however you have to matuch your front gear ratio. Your best bet would be to try to find a front axle out of a 4cyl car with 3.54 gears and find a rear axle with 3.55 gears. A Mustang axle wouldn't be worth the trouble
 An Explorer axle would work but may ne heavier than the Jeep axle and I've only seen them with 3.73 and lower ratios(higher number).

[blk-majik]

Great info, thanks guys I know I want a new trans, and I know I want rear disc brakes which seems easiest via a rear axle swap. Using that as a base, I think the most obvious way to make it happen is to just spec out the entire package around those two. If that means I re-use my front axle and transfercase, sweet If not, no big deal....

As far as transmission go, I see that later model Eagles came with a Borg Warner T5 5-speed. They're easy to find, cheap, and a pretty good trans. Google suggests that the swap is doable without too much drama. Does that seem to be the general consensus? Anyone here ever do this swap? Any other transmissions that are easy to swap in that are worth considering?

If the T5 is the best way to go, I know they're available from other platforms with different gear ratios. I had to guess on the numbers a bit, but if they're reasonably right, I calculate that the Eagle can hit just over 130mph with T5 out of an early 80's camaro or mustang. Would those trans swap in just as easily as a T5 from another AMC or Jeep? While on the subject, anyone know the gear ratios of the T5's that that Eagle came with?

this summer, i took the amc 15 out of my '79 spirit, and put in a frodulant 8.8 3.73 tracloc out of an explorer for my race car. the amc 15 axle, i could curle it no problem. 120lbs MAX. the frod axle, FORGET IT. i could BARELY pack it. its ATLEAST twice as heave as the amc axle.

Really? Wow, everything I read said that the 8.8 was relatively light! Oddly, the Mustang guys even thought they were light though... Either way, I guess perspective changes a lot when trying to consider road racing applications for rock crawling sources I may as well get used to that now. For a good laugh, try searching for ways to lower a Jeep 

[Sunny]

Really? Wow, everything I read said that the 8.8 was relatively light! Oddly, the Mustang guys even thought they were light though... Either way, I guess perspective changes a lot when trying to consider road racing applications for rock crawling sources I may as well get used to that now. For a good laugh, try searching for ways to lower a Jeep 

I can assure you the 8.8 is not that light. With the weight it's over 170lbs with the brakes.
It'll probably hold a lot more power than the AMC axle will though.

[maddog]

if you are wanting to go to disk brakes on the rear i believe i read that one of the guys on here swapped in a regular Cherokee axle and then used the disks from a newer model grand Cherokee and that they bolted right on without any modifications.

[eaglefreek]

You can't convert a 2wd T5 to 4wd. Jeep or Eagle T5 is your only option for a T5 and as said previously, is not a World Class and would not handle much abuse . A Jeep AX15 is an option but requires some work to get it in there. A manual valve body A998 might do the trick.

[blk-majik]

I finally got some time to get back to work on this. For now, I'm forgetting about transmissions and axels and everything other than the engine. Without an engine, the rest is useless. So i'm putting on blinders for a bit

I've been trying to decide if I really want to do the more ambitious EFI conversion with a head swap, or just throw a new carb on and hope for the best with everything as it is. Given the condition of the carb, and the filth around the valve cover gasket, I decided that I can't make up my mind until I pull the valve cover and intake manifold to get a better look at the condition of the head and valvetrain.

First off, there's a flex hose between the intake and exhaust manifolds. Whats this for? And why is it so difficult to remove? Pretty sure I stripped the locking nut on both ends trying to get it loose

Anyway, after (mostly) pulling the intake manifold (and mostly pulling the exhaust manifold while trying to totally remove the IM), and pulling the valve cover, here's what I found

























Not the worst I've seen, but pretty close! This thing is a mess. And until the carb seized up, it ran like this! That's a testament for the reliability of the 258!

Anyway, I'm going to have to disassemble and clean the head anyway, so may as well swap it for a 4.0L head. Get a valve cover upgrade while I'm at it, plus higher compression. Whats everyone's thoughts on the status of the short block? If I'm digging that deep, I'll pull the crank, pistons and rods while I'm at it and add a new set of bearings and seals. Think the pistons and cylinder walls should be in good shape, given the upper portion of the head and intake ports are this messed up?

That said, the more immediate question is that of a shopping list for the pull-a-part. Luckily a local junk yard has some fairly well stripped 90's Jeeps that look to have their entire long blocks with most everything else cleared out. Should be easy to just yank what I need. And there lies the question: what do i need?

What year/model Jeep's have the right head? Just anything with a 4.0L, or would it be easier to pair to a 258 with a specific year? Are there variations between years, and if so, which are best for the 258 swap? Any specific casting markings to look for?

Besides the head itself, what parts of the valvetrain will I want? How about the cam?

What about intake and exhaust manifolds, throttle body, injectors, wiring harness and ECU?
Any other odds and end's I'll need to grab?

Being I'm working with an 81 block, I'm pretty sure I'll have to heave the bottom end tapped to accept head bolts larger than the 7/16.... 1/2" iirc. Any other machining I'll have to do? I've read a bit about the CPS needing relocated for some reason. Any idea if that will be an issue?

[blk-majik]

I can get a complete block with manifolds for $180... might be worth it since its not much more than the head+valce cover+manifolds. going to look over Joshpit's 4.0 swap guide once more. Might be easier.

http://www.amceaglenest.com/~iowaeagl/guide/index.php?title=Joshpit's_4.0_Swap_Article

Anyone know of any good free online VIN lookup tools to help figure out if the donor has a security system? Or an easier way besides bugging the dealership?

[blk-majik]

I went to a local pull-a-part and found more suitable Jeep's than I know what to do with I took tons of pics, but one thing I noticed is that I couldn't find any casting stamps on the heads. I got all the VINs and took as good of pics as I could, so hopefully you guys can help me figure out what's what

I got a 91 Laredo, mostly complete. The valve cover had both PCV valves pulled and was rusted. I'm a bit worried about rain water getting into the head/block via the PVC, but otherwise it had a full wiring harness, PCM, TB, coils, distributor, most sensors, TB, throttle cables, manifolds, starter, fuse box and bracket, fuel rails, injectors, etc. Mostly a complete engine bay. Here it is:



Next I found a 92 Laredo with what looked like a totally untouched and clean engine. I could see that the seal on the valve cover was shot, but otherwise it looked good. Also a complete package with full wiring harness, PCM, etc. Probably a better bet since it was in so much better condition. Any reason why a 91 would be better than a 92?



There was a 93 Cherokee of some sort that I spotted on my way out while the junk yard was trying to close. The distributor, coil and plugs were pulled, but most of it was still left in the engine bay. The otherwise it looked pretty good. Fuse box, wiring harness, pcm, manifolds, tb and linkage, fuel rail... all looked good.



There was a 94 Grand Cherokee. The distributor cap and plugs were pulled, exposing the shortblock to the elements. However, the valve-cover was still completely sealed, so the head is likely good. All the other stuff was there and looked good. The insurance company window markings indicated that it ran and drove before being scrapped, so that's a good sign!



And on the way out, I saw a 98 Cherokee with the valve cover, distributor cap, and manifolds already taken. The valvetrain looked better than than mine, even though these were exposed to the elements Will a 98 work?



So that's my options after going through about 1/2 the junk yard I'm sure I can find some others, but did I find any jackpots a swap or a at least a head donor? Opinions on the best option of these? I'm thinking the 92 looks best so far. And anyone know how to tell if the wiring harnesses on these cars have the security chip option?

[mudkicker715]

That shows where the stamp is. Just above the oil fill you see 7120.

[blk-majik]

Thanks mudkicker, I was looking on the side so no wonder I couldn't find it

casper - why are the 93-95's easier to swap than other models? Is it just a mounting issue? Think there would be any issues in using the block from a 93-95, but the electronics from a newer model?

I noticed a few significant changes in engine management on the 4.0's after 1999.  In 99, they switched to a JTEC+ PCM, which is easier to tune.

from 2000 and up used a distributorless direct ignition system. From a tuning perspective, I could create and ignition timing table using load vs rpm axis to optimize torque under all load situations.

I'm wondering if it would be possible to take just the block from a 93-95, and the ecu, harness, ignition and fueling system from a 2000. any thoughts?

[mudkicker715]

i think it was in 96 that they did away with the axle mount bosses on the block. the front axle on our eagles mounts to the left rear corner of the block. i dont know of any reason you couldnt use the later electronics on an earlier block tho.

it was there in 99 for sure. almost certain throughout the run it remained

[IowaEagle]

The bosses, as far as I know remained present to the very end, just not drilled out.  I wonder if the Chinese versions, probably still in production have them?

[blk-majik]

Found some low-level info on the wiring harness. Might be helpful if I end up going the full stand-alone route: http://www.painlessperformance.com/Manuals/65140.pdf

Has anyone here swapped a later model 4.0 into an Eagle? If so, any additional complications? I dont mind going a little out of the box with sensors and tuning, but I'd really hate to be the guinie pig in fabricating new engine mount brackets/

Also, can anyone give some feedback on the 'high torque' cams from the late 90's 4.0's? They're reference on the painless performance site and it's new to me

[dustybat13]

I noticed it has been a couple of months since you last posted, so I was wondering if you have made it any farther.

My input on an engine choice is that it would depend on if you are planning on keeping the stock ecm to run it, or going with a megasquirt. I think that there would be some benefit to going with the newer engine if you are keeping the stock ecm as long as there is not a problem with the security chip. If you go with the megasquirt, then I would go with an engine that gives you the most power potential for the least cash.

Either way, I am looking forward to hearing about what your next step is going to be.