How to: '02 limited 4.0 to 4.6 dohc swap

Today I started putting in the engine for my swap that I have been planning for over a year now. I have a 2002 limited v6 explorer. I bought a 4.6 dohc from Craigslist for $500 last summer. I have slowly bought parts here and there to do this swap. Then a month ago I bought a 2003 limited v8 explorer with a bad engine. To start with I pulled both engines and transmissions. Swapped steering shafts and racks. Swapped pcms, and all of the other obvious stuff. I got the 2003 running yesterday with the v6. Now I can concentrate on mine. I will be selling the 2003, for a small profit, after mine is driving again. I will post updates as they come. Hopefully I'll be driving in a week or two.

What was the DOHC engine out of?
Sure fills the compartment.

The engine is out of a '94 mark viii. It actually fits pretty well. i wish I could have found an Aviator engine or at least a later mark viii version. The intake setup would help on those engines.

Aside from it being the DOCH engine, I wondered how hard it would be to swap a 4.6 into my 4.0

The best thing I can suggest is finding a v8 donor at a junk yard. At least find a complete v8 engine with all of the accessories from an explorer or mountaineer. There are a lot of small things that would add up. I Think the biggest is the steering rack and steering shaft. You will also need both engine wiring harnesses all of the a/c lines and compressor. The compressor for an explorer is not real common. They did put the same one on econoline vans certain yeas. They are a small scroll type compressor on the v8. You will also need a v8 pcm and transmission. Also a v8 exhaust y-pipe. The mounts are all the same as well as the radiator and a/c condenser. The cooling fans and fan shroud are different the v8 one is thinner. And when you get it all together, you will need to get your keys reprogrammed to the the pcm. I am doing my swap at work to make things easier, since I work at a ford dealership. Again, the best advice I can give is find a complete donor truck. I paid $1300 for the one I bought and should be able to sell it with the v6 now for $2500 or so. If you have the tools to do it, I say go for it. There are 5 or 6 v8 explorers right now on Craigslist in my area for less than $1000.

It runs! Not drivable yet, still need to put cooling hoses on and I just ordered intake tube that hooks throttle body to maf sensor. It sounds real nice.

Any idea what you expect to gain from it? How much horsepower or what have you?

The engine was rated at 285hp in 95. They changed the exhaust a few years later and rated it at 305. Torque was around the same, 300 or so. But the main benefit I see is its a better starting point. Possibly down the road doing a turbo or supercharger. I was just going to put a turbo on the 4.0, but I have always wanted to have one of these engines and it popped up on Craigslist.

Interesting swap

I've always been drawn to DOHC engines. Over the years I've owned 5 Jaguars, an Alfa Romeo and soon to be donated Volvo turbo wagon with dual cams. But I've never had a V8 with them. I was tempted a few years ago to purchase a MK VIII but decided it was too big. Also, I learned that the electrical wiring was a nightmare and the headlight lenses were ridiculously expensive.

I'm impressed and interested in your swap. What transmission are you using and how robust is it? As I recall the 4.6L has fairly limited overbore and overstroke potential so forced induction would be a good choice for significant performance improvement.

I agree about the mark viii, I like the idea of the car, I think it was just too much for the time as far as technology. When I bought the engine it came with all of the wiring from the donor car, engine and chassis harness. I couldn't believe how much wiring there was. I am not using any of the mark viii stuff. I remade the v8 explorer harness and grafted in a dohc navigator harness I have. I also updated the ignition to coil on plug instead of the dual coil mark viii setup. I just had to change valve covers. As far as the trans goes, I rebuilt a stock explorer trans. Since the lincoln aviator has this engine and trans combo I knew it would be okay. I am a ford senior master technician and I am the transmission tech at a ford dealership. I have had several of these explorer transmissions apart and there isn't a single difference in the strength of the v6 vs v8 trans. They are 99% identical on the inside. That includes the aviator trans. I feel it will hold up just fine.

5r55e?

I did a little internet research on the Aviator and was surprised to learn that the 4.6L DOHC V8 was mated with a 5R55E in some models. Is that correct? That's the same transmission I have in my 2nd Generation Sport and I've been concerned about it being able to hold up to the increased torque of my supercharged 4.0L SOHC V6. Are you using the 5R55E?

No, 2002 and up explorers have either a 5r55w or 5r55s. They are loosely based on the 5r55e that your explorer has. The only difference between the w version and s version is 2nd gear ratio. And it's a very slight difference. There is also a 5r55n that was used in lincoln LS, t-bird, and mustang. It has a different solenoid pack and an extra clutch pack. It also has the "manual" shift mode. The 5r55e that you have was a smaller trans with a removable bellhousing/pump assembly. Some of the internals will interchange between them all. I would say the power handling capacity is pretty close to each other. The cases look a little more stout to me, but I have zero facts to back that up. They all have common problems, but with a proper rebuild, they can all be remedied and improved.

Increasing interest

I have to admit that my interest in your swap is increasing. I assume that the reason you swapped the steering shaft and rack from the 2003 to the 2002 is because the configuration is different for the V8 engine.
Is any 3rd generation Explorer with a V8 suitable for the DOHC V8 swap?
Is there any difference in the short blocks for the 4.6L SOHC vs the DOHC?
Will the stock DOHC exhaust manifolds fit without modifications? I think the 2nd generation engine compartment is too small for a V8 with high flow exhaust manifolds but I don't know about the 3rd generation.

I looked at the specifications for the Aviator which was based on the Explorer. It weighs about 500 lbs more and I don't like the front. There might not be room for a positive displacement supercharger but stroker kits are available to increase the displacement to 5.0L. That would make a pleasurable midsize SUV to drive.

Is there any mod to make filling the 5R55W or S with ATF a reasonable process?

You are correct, the steering rack and shaft are v8 specific. The v6 parts will not work. I used aviator exhaust manifolds. The exhaust ports are different from sohc to dohc. The factory explorer v8 exhaust bolted right up to the aviator manifolds. As far as the chassis, any 3rd gen will work. The engine mounts are even the same form v6 to v8. There is a seperate adapter plate that goes from mount to engine that is specific. For the most part, all 4.6 blocks are the same. The explorers used an aluminum block as did the Cobras and mark viii. Also aviator and some expeditions. The 4th gen explorers switched back to iron blocks when they went to the 3 valve heads. I think the 2nd gen explorers are a little too small also. If you wanted to go that route I would look for a 302 or 351w based swap since they already had 302 in them. If you find a 3rd gen v8, a dohc will drop right in with only the exhaust manifolds and wiring harness changes. I would have just done that, but the '03 donor that I bought had some pretty bad rust on the pass rear, which mine has none. There is plenty of room for a roots blower on top. I would probably go with a turbo setup since my engine has the twin port "B" heads. I am having trouble finding an affordable intake to fit my heads and mount a blower. The single port heads have factory parts for that since the 03 and 04 Cobras have that engine. If you do this swap, get an engine with "C" heads. Basically 2000ish engines are all this setup. I would suggest finding an aviator engine. Or a wrecked aviator. Take the engine, both engine harnesses and all the accessories. The radiator setup is different on the aviator also. And they have an additional electric cooling fan. Lots of little things. Plus the brakes are a nice upgrade.

COP ignition

87350gta said:

. . . I also updated the ignition to coil on plug instead of the dual coil mark viii setup. I just had to change valve covers. As far as the trans goes, I rebuilt a stock explorer trans. Since the lincoln aviator has this engine and trans combo I knew it would be okay. . . I have had several of these explorer transmissions apart and there isn't a single difference in the strength of the v6 vs v8 trans. They are 99% identical on the inside. That includes the aviator trans. I feel it will hold up just fine.

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I've been doing a little internet searching on the 3rd gen Explorer and the Aviator. It looks like the Explorer had the 5R55W thru 3/3/2002 and the 5R55S from 3/4/2002. All of the Aviators had the 5R55S but there are different IDs for different years of 2WD:
2003 Aviator 2WD: ID 3L2P-EB
2004 & 2005 Aviator 2WD: ID 4L2P-EC
Do you know what the differences are for the two IDs?
Anyway, I guess I should purchase a 3/4/2002 or later Explorer for compatibility.

I've read that the head covers retain heat causing the COPs to overheat and prematurely fail. Some Aviator owners have reverted back to dual coilpacks.

I also read that there was a head cooling problem on some of the 4 valve 4.6 engines in the Cobra SVTs, Marauders and Aviators. The rear valves overheat and prematurely fail. Do you happen to know what year and model of heads don't have the cooling problem?

The 2002 and 2003 are interchangeable. In 2004 the solenoid pack changed design. The explorers also switched pcms and went to fly by wire. You cannot switch a 2002-2003 solenoid pack with the newer versions. I have tried. The aviators never went to fly by wire, not sure if the solenoids changed on those. I have only done a few aviator transmissions, since I don't work at a lincoln dealer they don't come in that often. I haven't heard about the rear valves overheating, they do have valve seat issues that might be caused by overheating. So we might be talking about the same thing. As far as the cop vs dual cool setup, that is probably true, but I am not worried about that. I will deal with changing coils instead of dealing with plug wires and coil packs. Just for esthetics alone. I will check on the later trans solenoid when I get back to work after lunch.

COP vs coilpacks

Thanks for the information. I'll be looking for a 2002 after 3/3/2002 or a 2003 because of the electronic throttle control.
I think that a COP has a better spark than a coilpack and agree the COP wiring is cheaper to maintain, looks better, and takes less engine room.
I found more information on the head cooling problem: Head cooling mod

I don't know if you need to go for the late build 2002s. My explorer is an early 2002 and I put the engine/trans/pcm into an 03 with zero problems. The early build 2002 had a lot of little differences, but not enough that I would avoid them all together. As long as the pcm matches the trans year, you should be fine.

aluminum or cast iron block?

87350gta said:

I don't know if you need to go for the late build 2002s. . .

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I was thinking that the 5R55S might be better suited to the DOHC since that's what was in the Aviator.

Which block has the better boring and stroking potential - aluminum or cast iron?

Apparently the head cooling problem was fixed and incorporated in the 2005 Aviator. Can I use the 2003 Explorer 4.6L block and just bolt on the DOHC heads, intake manifold, etc?

I don't want to hijack your thread so I've started my own if you want to answer there: Next project vehicle?

I was unaware of the cooling system mod. I really wish I had known about it before I put the engine in. I will figure something out before I start beating on it too hard. I made some progress tonight. Just have to hook up one coolant hose and the heater hoses. Air intake tube arrived today. It will need modified to work with my factory air box. I so wish I had gone with the newer mark viii intake or an aviator engine. You sure can just put the heads and all the other parts on a regular explorer block. ypu will still need intake and timing cover and all of the other timing parts. Plus a bunch of other small parts. But the blocks are basically the same. I am not sure on the bore and stroke capacities. I have honestly never looked into that on a modular engine.