Details of an Eagle 4.0 swap

Swaping 258 to 4.0, 4.0 parts to 258 etc!

Details of an Eagle 4.0 swap

Postby TheDarkSideofWill » September 11th, 2010, 5:40 am

I have an '85 AMC Eagle Wagon 5 speed. I would eventually like to build a stroker for it, but in the interests of having it running with EFI this winter and in only taking on one project at a time, I'm going to do a 4.0 swap first.

Upon first inspection, it appears that the areas of interest are the following:

Engine Mounts: I @$$ume that the 258 engine mounts bolt right up to the 4.0 block.

Front Differential: I've heard that all the bolt holes to mount the Eagle front diff on the 4.0 are still in the block, but some stiffening ribs on the later (98+?) NVH blocks must be ground down or otherwise modified. Does anyone have a picture of this?

Bellhousing and flywheel: I @$$ume that any 258 flywheel is mechanically compatible with the 4.0. I'm not concerned with crank triggering, as I will be using a GM ECM which gets its trigger signal from the distributor. I want to use the lightest flywheel I can. I am aware that conventional wisdom likes a heavy flywheel for offroading. I'm also @$$uming I can retain the bellhousing that my car currently has.

Exhaust: I've been told that all 4.0 factory exhaust manifolds or aftermarket headers will require modification to not occupy the same space as the Eagle front diff. Is this the case? How many different exhaust mnaifolds were used? What are the common headers? Which ones are best for power? Which ones are easiest to modify?

Accessory drive (Air Conditioning): What years of the 4.0 used a serpentine drive vice multiple V-belts? My car has air conditioning. What do I need to know about the compressor sizing and designation to understand how to make my system work properly after the swap? What's the "swapology" of pulleys and compressors?

In general, I want the newest engine available. I understand the 0331 head has tendencies to crack which are less prevalent in the newer engines. I also understand that the newer intake manifold is better. I am aware of the coil pack ignition and intend to discard it in favor of the aforementioned GM-based distributor.

Thoughts? Comments? Anything I'm wrong about? Anything else I need to know?
Thanks!
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Re: Details of an Eagle 4.0 swap

Postby amcinstaller » September 11th, 2010, 8:14 am

check this site, if you havent already: forums.amceaglenest.com

looks about right so far though,

engine mounts are identical, use the 258 motor mounts, obviously

front diff requires bolck mods or a bracket to be fabbed

258 flywheel will bolt up, but you need to use the big ugly 258 starter, and the solenoid on the fender

exhaust i tihnk hits, but check the nest for details

not sure about the a/c, but i think most 4.0s, if not all came with serp belts.

and yes the heads you mentioned did crack, theres an 0331 head thread here, read it and the 99+ intake is supposed to be better.
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Re: Details of an Eagle 4.0 swap

Postby SilverXJ » September 11th, 2010, 9:01 pm

TheDarkSideofWill wrote:Accessory drive (Air Conditioning): What years of the 4.0 used a serpentine drive vice multiple V-belts? My car has air conditioning. What do I need to know about the compressor sizing and designation to understand how to make my system work properly after the swap? What's the "swapology" of pulleys and compressors?

All 4.0Ls have a serpentine belt. No V-belts

In general, I want the newest engine available. I understand the 0331 head has tendencies to crack which are less prevalent in the newer engines. I also understand that the newer intake manifold is better. I am aware of the coil pack ignition and intend to discard it in favor of the aforementioned GM-based distributor.
The 03+ o331 head has teh issues fixed. But keep in mind that those engines with teh ehad will be from a WJ or TJ and that the engine brakets moutning boses and various other accesories will be different from earlier years and vehicles (i.e. non WJ, XJ and 99 and earlier TJ)

BTW I see your axle post on speedtalk
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Re: Details of an Eagle 4.0 swap

Postby TheDarkSideofWill » September 12th, 2010, 3:28 pm

amcinstaller wrote:check this site, if you havent already: forums.amceaglenest.com
looks about right so far though,
engine mounts are identical, use the 258 motor mounts, obviously
front diff requires bolck mods or a bracket to be fabbed
258 flywheel will bolt up, but you need to use the big ugly 258 starter, and the solenoid on the fender
exhaust i tihnk hits, but check the nest for details
not sure about the a/c, but i think most 4.0s, if not all came with serp belts.
and yes the heads you mentioned did crack, theres an 0331 head thread here, read it and the 99+ intake is supposed to be better.


Thanks for the info!
I'm already a member at Eagle's Nest. I've been asking driveline questions there. It seemed like this might be a better place for detailed info on the year-by-year changes to the 4.0.

-What's obvious about using the 258 engine mounts? Keep in mind I've never investigated a 4.0 in its native habitat. Is the reason to use 258 mounts obvious once I look at the parts?
-So for the front diff mount to an NVH (or any?) block, I'd have to either grind the ribs down OR modify the brackets to clear the ribs, BUT the bolt holes are all in the right locations. Is that correct?
-Do the 258 and 4.0 flywheels have different tooth counts on the ring gear? Is that why I would have to use the big ugly 258 starter?

SilverXJ wrote:
TheDarkSideofWill wrote:All 4.0Ls have a serpentine belt. No V-belts

The 03+ o331 head has teh issues fixed. But keep in mind that those engines with teh ehad will be from a WJ or TJ and that the engine brakets moutning boses and various other accesories will be different from earlier years and vehicles (i.e. non WJ, XJ and 99 and earlier TJ)

BTW I see your axle post on speedtalk


Thanks for the info here and at SpeedTalk!

Good to hear about the serpentine belts... Can I swap pulleys on the AMC A/C compressor and keep it, or do I have to open the system and install the Jeep compressor?

Is there a pictorial or other explanation about what changed for the '03 engines? Were the block changes implemented in '03? What work is necessary to use an '03+ engine in an older body?
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Re: Details of an Eagle 4.0 swap

Postby SilverXJ » September 12th, 2010, 3:38 pm

03+ is the range for the non-crack prone 0331 head.

I don't recall all the specifics on the 99+ WJ/00+ TJ block any more. I know the engine bracket bosses are a different height and in different spots, the water pump mount is different and I think a few other details.
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Re: Details of an Eagle 4.0 swap

Postby amcinstaller » September 13th, 2010, 11:56 am

i meant jeep vs eagle motor mounts, cant use the jeep ones, theyre way different. same bolt holes though. thought you already knew that, sorry :doh: and the difference in starter comes in i believe depth of the ring gear. but if youre planning to use efi, id try the newer flywheel, im not sure the wieght is much different, at least it didnt feel much different to me, ive lifted both a 90ish and an 80 from the spirit around my garage for the last 2 years :roll:

just noticed (again) your name at the nest.
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Re: Details of an Eagle 4.0 swap

Postby TheDarkSideofWill » September 14th, 2010, 12:46 pm

amcinstaller wrote:i meant jeep vs eagle motor mounts, cant use the jeep ones, theyre way different. same bolt holes though. thought you already knew that, sorry :doh: and the difference in starter comes in i believe depth of the ring gear. but if youre planning to use efi, id try the newer flywheel, im not sure the wieght is much different, at least it didnt feel much different to me, ive lifted both a 90ish and an 80 from the spirit around my garage for the last 2 years :roll:

just noticed (again) your name at the nest.


Thanks. Understood mounts now. I was thinking Chevies, for which the engine mounts are almost universal and only the mount towers on the body are different by platform.

If the 4.0 starter is lots smaller and lighter and doesn't need the solenoid on the fender, then I'd like to use it. I may do something slightly fancy with the flywheel and ring gear... we'll see.

SilverXJ wrote:03+ is the range for the non-crack prone 0331 head.

I don't recall all the specifics on the 99+ WJ/00+ TJ block any more. I know the engine bracket bosses are a different height and in different spots, the water pump mount is different and I think a few other details.


Is there a primer someplace that lays out year and model for each of the chassis codes? Is the 99+ WJ/00+ TJ block the "NVH" block?
By engine bracket bosses do you mean engine mount bracket bosses? Or the accessory drive? Does the Eagle front diff still bolt up to the later block?
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Re: Details of an Eagle 4.0 swap

Postby TheDarkSideofWill » October 17th, 2010, 7:16 am

Found this primer on Jeep chassis codes: http://www.kevinsoffroad.com/identifyyourjeep.html

I'll have to do more research into the block casting numbers to figure out exactly which one I want and exactly how it will mount in the Eagle.
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Re: Details of an Eagle 4.0 swap

Postby EFIeagle » November 21st, 2010, 5:37 pm

I'd recommend swapping the head for a 7120 casting. They're reliable, and have much higher volumetric efficiency.It should be a direct swap onto the block. You'll also be able to retain your coolant temp sensor, as the later heads did not have the port for the sensor which sends signal to your gauge. ALso, the 99 up intake manifold is good because of the supercharging effect close to redline, but the older manifolds have larger runners, allowing you more room for bolt on improvements, like a 60+mm tb, CAI, etc. The 258 mounts will bolt right to the 4.0 mounts, you will not be able to use the 4.0 mounts. Don't bother trying to modify your manifold and risk cracked welds within 10,000 miles, just modify the diff bracket, it's extremely easy with some 3/16 or 1/4" thick steel strip and 3/4" square tube, and longer bolts from Lowes.
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Re: Details of an Eagle 4.0 swap

Postby TheDarkSideofWill » November 21st, 2010, 7:23 pm

I'm not going to swap the head on the 258.

The chambers already overhang the bore on the 4.0, which causes enough problems. I'm not going to make that worse by continuing to use the smaller bore block.

Besides, I'm a believer in modern engineering. Modern design tools do *sooo* much better on the "invisible engineering" aspect of stiffness, thermal growth, etc than old school hardware could hope to be. I'll go at least to an NVH block. I may find a new 0331 head to swap onto it if I decide that the newer blocks are worth the struggle to adapt.

If I do anything with the 258, it will be yank the crank out to make a stroker, but I'll probably stick with the older fully counterweighted crank for that.
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Re: Details of an Eagle 4.0 swap

Postby amcinstaller » November 22nd, 2010, 8:34 am

TheDarkSideofWill wrote:I'm a believer in modern engineering. Modern design tools do *sooo* much better on the "invisible engineering" aspect of stiffness, thermal growth, etc than old school hardware could hope to be.


THANK EFFING GOD!!!!

i hate it so much when people wanna hang on to ancient technology. i mean yea, numbers matching big three muscle is one thing, but im not seeing amc eagle values going up any time soon, or any other amc for that matter. (hides from flaming :lol: )dont get me wrong, i love my 1980 spirit, but im not expecting to ever sell it for more than a thousand bucks. good choice on the 4.0 swap, and hopefuilly a stroker!
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Re: Details of an Eagle 4.0 swap

Postby TheDarkSideofWill » January 13th, 2013, 7:57 am

Thread Resurrection!

I have a '91 4.0 (Price was right) and I'm installing the Eagle oil pan and pickup to it.

However, the Eagle pickup in the 4.0 pump doesn't seem to work with the Eagle pan. The pan won't seat all the way, and the bolt hole in the mounting strap doesn't line up with the bolt hole on the pump.

Comparison of Jeep and Eagle oil pickup tubes:
Image

Frustrating... The Eagle oil pump pickup is fully seated in the Jeep oil pump, but the hole in the securing strap does not line up.
Do I need an Eagle oil pump in addition to the pickup?
Image


Do the 4.0 and 258 use the same oil pump? Is my pickup bent or otherwise mangled?
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Re: Details of an Eagle 4.0 swap

Postby SilverXJ » January 13th, 2013, 9:15 am

According to rock auto the 4.2L and 4.0L take the same pump, but different pickups.
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Re: Details of an Eagle 4.0 swap

Postby amcinstaller » January 13th, 2013, 7:52 pm

thats very interesting. i havent seen anyone encounter that issue before. mark, remove, drill, make work i guess?
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Re: Details of an Eagle 4.0 swap

Postby TheDarkSideofWill » January 14th, 2013, 8:04 am

It doesn't *LOOK* bent, and my dad says he was careful when removing it from the 258 pump...

BUT, it doesn't fit here and it hits the pan when I try to drop the pan over it. The bottom of the pickup is 8 1/2" from the pan rail on the block and the pan itself is 8 3/8" deep.

I guess the only conclusion to draw--especially since no one else has had this problem--is that it got bent somehow... I guess I'll just bend it back until it works, but I won't be able to work on it again until this weekend.
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