Vehicle: 1999 Ford Explorer Sport w/ 4.0L OHV, 4.10 gears, and ~45k miles

Donor: 2000 Mercury Mountaineer 5.0L V8 Rollover, ~43k miles

Parts needed:
-Complete explorer V8 engine with all wiring, vacuum hoses and accessories
-V8 engine mounts (V6 ones work, but the V8 ones are slightly larger)
-Starter motor
-Stock V8 exhaust with O2 sensors and cat converters (or go custom if you like)
-Engine bay wiring harness
-Radiator & hoses
-Brake booster
-Cruise control servo
-Throttle cable
-Trans Shift cable
-Cruise control cable
-Complete 4r70w transmission with sensors and wiring
-Transmission cooler
-Transmission cooler lines
-Power steering lines
-Power steering cooler
-Hard AC line that bolts to compressor and goes to the dryer and condenser
-A few extra bolts to mount trans cooler, wiring harnesses, wiring brackets.
-AWD transfer case (not needed for 2wd)
-Front driveshaft (not needed for 2wd)
-Shortened 4 door V8 rear driveshaft to fit the sports shorter wheelbase
-2wd GEM (behind and left of radio), ECU (engine bay), PATS module (above Pass. Airbag), and a key. All these need to be from the same vehicle except for the GEM in order to avoid going to the dealer for programming. If you want to use your existing key, then you only need the ECU and a trip to the dealer for programming.

Modifications I did:
Some paint & new bolts
Comp cams 986 springs with retainers and locks
Comp cams 349 cam
1" Trick flow upper intake spacer
Torque monster headers
TransGo Shift kit for 4R70W
FMS Double roller timing set
FMS metal lifter guides (to replace the stock nylon parts)
1.6:1 Roller rockers
FMS cast aluminum valve covers (no purpose really except to look cool and possibly clear rocker arms)
Taylor Plug Wires
Fel Pro gaskets
FMS head gasket kit with bolts (gaskets are made by fel pro though)
Alternator from a sport trac with 23k miles or so

One thing to note about this swap, is that it is 100% bolt in if you have all the right parts. All holes are drilled in the frame/engine bay area for the new wiring clips, trans cooler and other brackets. The way I recommend doing this swap is to have a donor vehicle. It is so much easier and you are guaranteed to have all the necessary parts

Pics:

I spent a lot of time working on this motor before I actually started taking apart my X to swap engines:

After the first full day of work, we had the engine out:

Next I did some undercoating of the trans tunnel, rust repair in the engine bay, and cleaning. Then I installed the V8 engine bay harness. I find this to be a necessary part because the engine wiring connector is located in a different spot from the V6 to V8. I didn’t feel like extending all the wires, since I had a complete harness. Also, this harness was wired for the EATC system and message center, which I had installed earlier, so having factory wiring for that is a big plus. I also came to a problem when I started to install the V8 power steering lines that I bought from fast parts network. They fit fine, but for some reason my power steering cooler wasn’t lining up with the lines! I said oh crap, because I had sold my power steering cooler way back to a fellow member. I did not realize that they are different. I immediately ordered one from ped5stang, and decided to make my current one work for the time being.

Once this was all complete, a friend came over and we replaced the head gaskets and checked for debris in the combustion chamber. The engine was sitting around a good bit and I wanted to make sure there was no junk in there. We managed to also remove a good portion of any carbon build up using solvents and a toothbrush. After this, we got the trans under the vehicle and lowered the engine in place. The V8 is a big engine and is a tight squeeze into the X. With the harmonic balancer installed, there was only about 1.5 inches from the hood weather strip at the firewall to the radiator support. You absolutely need another person to help when mating the engine and trans. One person under the truck with the trans and jack, and one above operating the hoist and tilting the engine. With some good communication, things go fairly quickly.

Once we got the engine in, we called it a day and the next day I started installing as many parts as I could. I installed the t-case. What a pain that was. It was for some reason really hard to lift it up in place while under the vehicle. I got it up there and was quite happy with myself. I then decided to take my sports rear driveshaft and hold it in place. To my surprise, it was the proper length! I was quite happy until I realized that the front flange on the driveshaft wasn’t lining up with the transfer case flange. The bolt patterns on the flanges are different from V6 to V8 I guess. After realizing this, I wasn’t ready to give up. I tried to swap out the front yokes, but realized that the splines were very different also, so that couldn’t be done either. I probably could have swapped out the front flanges themselves, but with the amount of rust, there was no way I was going to get the u-joint out intact. I decided to bring the mountaineer driveshaft out to a shop and get it shortened for $45. I believe my measurement was 37.5” flange to flange. This way, I have the proper driveshaft, as it had a slightly larger diameter anyway. The thing fit like a glove once I got it back home.