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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
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1,058 Posts
Discussion Starter · #1 · (Edited)
I wasn't planning on doing this swap yet, but my timing cover likely needs to be replaced due to a broken off coolant nipple. I figure, it'd probably take the same amount of labor to swap in a 3.8L complete engine from the junkyard. But then, it'd only be a little more work to swap a 4th gen long block with 3rd gen externals.

Current 3.3L 158hp 203ft/lbs
3rd gen 3.8L 180hp 240ft/lbs
4th gen 3.8L 215hp 245ft/lbs
SOHC 4.0L 253hp 262ft/lbs


Maybe now is the time to try the SOHC swap I'd been researching

What I know-
The 3.5/4.0L engines have or can use the same flex plate as a 3.3/3.8L engine.
The 3.5L/4.0L can mate to a 41TE transmission.
The LH Platform had the 3.5L, and also offered a 3.3L, and the PCM wiring is very similar to the minivans.
Dodge put a 3.5L in their Caravan R/T Concept.

What I don't know-
Will the SOHC engine physically fit? I've heard that it's close, but slightly too big. I may have to rework the transmission mounts to move the drivetrain forward an inch, so the rear head will clear the firewall.
Will the LH Platform PCM communicate with the 3rd gen minivan BCM, TCM, and instrument cluster? I can only guess. It seems likely that these systems will have generic communication protocols, but this is purely a crapshoot. There is no way of knowing until the swap is complete and the engine is started...
Engine plumbing and accessories. I'm assuming I should use the Pacifica accessories if possible, since it is FWD. I will likely need many sensors and electronics off an LH in order to use the LH PCM.

I'll need to fabricate a custom wiring harness. I'll need to fabricate the engine plumbing. Custom exhaust will be required. The front motor mount will likely need to be fabricated, the left/front transmission mount may need to be modified.


Anything else anyone can offer? Somebody needs to guinea pig this swap, it hasn't been done but I'm hoping it is possible and feasible, I'm willing to try it.



***It is a go, I just secured a loaner pickup truck for the indefinite future until the swap is done.
 

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2008 Chrysler Town & Country Limited 4.0
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718 Posts
I don't have any answers, but I can tell you the 4.0 is a strong engine for the minivan. Our previous minivan was a 2000 Ford Windstar with the 3.8, maybe 200 hp. It always felt weak except for the low-end torque. The 4.0/62TE combo works very well, but the 41TE should also do well with the broad torque band of the 4.0.
 

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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
Joined
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1,058 Posts
Discussion Starter · #3 ·
I don't have any answers, but I can tell you the 4.0 is a strong engine for the minivan. Our previous minivan was a 2000 Ford Windstar with the 3.8, maybe 200 hp. It always felt weak except for the low-end torque. The 4.0/62TE combo works very well, but the 41TE should also do well with the broad torque band of the 4.0.
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Plus, I swapped the 3.61 final drive ratio for 4.09 gears. It's gonna run like a scalded dog if I can manage to cram that motor in there.
 

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2013 Dodge Grand Caravan
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2,700 Posts
Need wiring diagrams? My favorite free source shut down last year, but I can still get everything from work. Just tell me what you pull the motor from and I can get you full diagrams - and more than likely in color.
 

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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
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1,058 Posts
Discussion Starter · #5 ·
I've made progress, 4.0, here we go!


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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
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1,058 Posts
Discussion Starter · #6 ·
The 41TE bolts up! 5 of the 7 holes transmission bellhousing bolt holes line up with the 1997 transmission I have laying around. Based on pictures I have, 6 of the holes line up on the 2001 transmission in my van currently.
The bolt hole that doesn't line up with either 41te should be on the oil pan, so maybe another 3.5L oil pan has the hole to make all holes line up


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2009 GCV SE
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1,264 Posts
You're making me jealous because I want the 4.0L in my 2009 :(

How many miles does it have?
 

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3rd gen > all others
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3,533 Posts
Think it's any lighter than a 3.3/3.8? That would be another plus. Dang, hot rod minivan!! Following!

You're also making me want to procrastinate even more on my engine swap. Why put another 3.8 in it if I can get a 4.0 in there? Almost looks like the threaded holes are there on the lower backside of the block for the AWD transfer case bracket. Hmmmm....

That lowest hole on the transmission that doesn't line up with anything - - goes to the steel stiffener brackets that bolt to the rear of the block. I just dropped a transmission out of the 2001 AWD I've been getting parts from at the U-Pull today. Finally got the thing out on the 3rd day of working on it. Had to get all of the AWD drivetrain out of it first, and the steel cradle plate and CV shafts. Laying in the melting snow, dripping coolant and transmission fluid, rust flakes falling in my face - not fun. The prize is a 41AE with 126k miles, on a van that was kept up and no trailer hitch. The front hubs were shot. Van should've been fixed, not junked! It should be a good one. Would have much preferred the weather you had while pulling parts! Then again, this is why winter is the best time to go junkyarding - only the hardcore vultures go into the yard, so more parts available! :LOL: I got the torque converter and flex plate too, and didn't get charged extra. :)
 
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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
Joined
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1,058 Posts
Discussion Starter · #9 ·
Think it's any lighter than a 3.3/3.8? That would be another plus. Dang, hot rod minivan!! Following!

You're also making me want to procrastinate even more on my engine swap. Why put another 3.8 in it if I can get a 4.0 in there? Almost looks like the threaded holes are there on the lower backside of the block for the AWD transfer case bracket. Hmmmm....

That lowest hole on the transmission that doesn't line up with anything - - goes to the steel stiffener brackets that bolt to the rear of the block. I just dropped a transmission out of the 2001 AWD I've been getting parts from at the U-Pull today. Finally got the thing out on the 3rd day of working on it. Had to get all of the AWD drivetrain out of it first, and the steel cradle plate and CV shafts. Laying in the melting snow, dripping coolant and transmission fluid, rust flakes falling in my face - not fun. The prize is a 41AE with 126k miles, on a van that was kept up and no trailer hitch. The front hubs were shot. Van should've been fixed, not junked! It should be a good one. Would have much preferred the weather you had while pulling parts! Then again, this is why winter is the best time to go junkyarding - only the hardcore vultures go into the yard, so more parts available! :LOL: I got the torque converter and flex plate too, and didn't get charged extra. :)
I think it's 30-50lbs lighter, just based upon 2nd and 3rd hand internet myths. Aluminum block instead of cast iron.


It was in the high 50's today, kind of chilly.

Remember, the Pacifica had the 4.0L and AWD PTU. "Theoretically", the AWD will bolt up.

Let me go through this process first, who knows what issues await and whether this is feasible. Either-
4.0L requires piggyback ECU
4.0L is viable on 1st gen LH electronics
3.5L is viable on 1st gen LH electronics

4th gen 2004+ minivans are a different story, they'd electronically want a 3.5L HO from a second gen LH.
 

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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
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1,058 Posts
Discussion Starter · #10 ·
You're making me jealous because I want the 4.0L in my 2009 :(

How many miles does it have?
193,000.
😬

There was a really sweet T&C with 76k that had been in a collision I went to pull the motor out of, somebody had already taken it in less than a week. All the 4.0L Nitros and Pacificas too.
 
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2013 Dodge Grand Caravan
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2,700 Posts
Better do that timing belt while you have easy access. :p
 

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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
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1,058 Posts
Discussion Starter · #12 ·
I ordered the timing kit, complete gasket set, Inertia Motorsports V1.2 camshafts, and two cans of genuine Mopar Hemi Racing Orange engine paint.
Still need to pressure wash the motor and start tearing it down to see the condition of the rings and bearings.
I need to grab the camshaft sprocket out of a 1997 or older LH car and have my machinist weld the timing window ring from it onto the 4.0L sprocket. They 1st gen LH have the same SBEC computer system, the timing notches on the camshaft are identical to the 3.3 and 3.8L. They also use the same part number flexplate, whereas the 4.0L has the flexplate off of a 4th gen NGC minivan with 36 timing windows instead of 12.

I've changed plans, as of this moment I'm going to wire up the stock 3.3L PCM minus the coil and injectors. It should get a perfect timing signal and sensor data from the 4.0, in fact I'm sure it could run it, albeit sloppily. Next week I'm going to order a Megasquirt MS3X, and wire that up piggybacked to actually control the engine. The dumb factory PCM will be happy thinking it is running things, and keep the BCM, Instrument Cluster, and TCM running.

I threw some ebay headers onto the motor rather than buying new catalytic converter manifolds. The rear header might barely clear the transmission, otherwise it's going to need to be cut, bent, and rewelded. They are for a 05+ 3.5L Charger, but they fit the block at least.

61207
 

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3rd gen > all others
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If you're still planning on adding AWD later, that rear header will probably interfere with the transfer case. As it sits now, it looks like it would be blowing exhaust right onto it.

Edit:
I also researched exhaust manifolds for this. Looks like the Pacifica 3.5 exhaust will work, and it uses a crossover pipe from front to rear manifold, and a single downpipe connection with no catalytic converters. This could possibly work for a budget exhaust, and mate it to the van's factory catalytic converter/exhaust with a modified flex/connector pipe. This is getting more and more tempting.
 

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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
Joined
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1,058 Posts
Discussion Starter · #14 ·
If you're still planning on adding AWD later, that rear header will probably interfere with the transfer case. As it sits now, it looks like it would be blowing exhaust right onto it.

Edit:
I also researched exhaust manifolds for this. Looks like the Pacifica 3.5 exhaust will work, and it uses a crossover pipe from front to rear manifold, and a single downpipe connection with no catalytic converters. This could possibly work for a budget exhaust, and mate it to the van's factory catalytic converter/exhaust with a modified flex/connector pipe. This is getting more and more tempting.
My goal/expectation when I get it dyno tuned is 300hp, I'm probably going to need AWD to keep that manageable.:D


Got it pressure washed and mostly torn down.
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Six bolt mains with crossbolted, a structural oil pan, and structural windage tray. This motor is a beast.
 

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1997 Chrysler Town & Country LXi AWD
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184 Posts
My goal/expectation when I get it dyno tuned is 300hp, I'm probably going to need AWD to keep that manageable.:D


Got it pressure washed and mostly torn down.
View attachment 61271
View attachment 61272
View attachment 61273
View attachment 61274
View attachment 61275


Six bolt mains with crossbolted, a structural oil pan, and structural windage tray. This motor is a beast.
Our recent run-in on Facebook just reminded me to check this thread. Good to see you're making progress and I'll have to say, that's a nice example of a stepside GMT800 you've got there.
 
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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
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1,058 Posts
Discussion Starter · #16 ·
I tore it down to a bare block this weekend. The timing on the rear bank cam sprocket was off by one tooth. The timing belt tensioner pulley was also loose.
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There is some scouring on the crankshaft bearings, rod bearings, crankshaft journals, and cylinder head camshaft bearing surfaces. The cylinder bores look great, still have a crosshatch pattern.

I'm going to get the crankshaft turned and the block honed/hot-tanked. New crank and rod bearings, new rings probably.

Debating whether or not I should go grab another set of cylinder heads. There isn't a replaceable bearing on the heads, the only way to clean them up would be to have them line bored and some kind of sleeves pressed in.


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3rd gen > all others
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You can't put sleeves in for cap-style cam bearings. What the machine shop could do is mill all of the caps a little bit so they're shorter, bolt them onto the head and torque them, then align-bore the heads to factory spec. Basically the same as how they resize the big end of a connecting rod.

I found a 2005 Pacifica with a 3.8, 41TE and autostick and it got me thinking. If that Pacifica didn't have security, would the PCM work in my van (2004)? They'd both be NGC and both have throttle cables. Is the bus system the same? Just wondering if that would be an easier way to add autostick. Maybe it would also require the instrument cluster to work, even if frankensteined into the 4th gen cluster? I didn't buy any parts yet. I just wanted to see if the concept is possible.
 

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3rd Gen Plebeian
1997 Plymouth Grand Voyager Rallye
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1,058 Posts
Discussion Starter · #19 ·
I've probably been posting too much in the "What I did Today" thread.
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I had the crankshaft journals turned 0.010" under, and the bores honed. I have all new bearings, rings, and oil pump. Just need to paint the block and assemble the lower end.

I decided to go with Mopar Hemi Racing Orange and Black.
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I've been porting and polishing the cylinder heads.
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The combustion chambers are all polished, and I did some work on the intake and exhaust ports. I haven't had time to finish the porting, I've been working too many hours. I'm also waiting on the Camshafts to ship from Crower.


I'll start updating here more
 

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3rd gen > all others
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Still waiting to get the engine block back from the machine shop AGAIN? I remember you posting that they painted it and got overspray inside of it, so you took it back to be re-cleaned/hot tanked. How did they handle that?
 
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