Well, I saw that their was an AMC V8 thread, so I figured I would try and start a 4.0 swap thread here. Feel free to ask any specific questions you have, as I am sure I will miss some things. Let me know what you think and if thre thread should be a sticky.
Engine mounting
Well, their is some good news here. Your CJ 258 motor mounts will work. You do not need to move any mount brackets, or even change the actual mounts.
Flywheel/flexplate
Depending on how you plan to mount your CPS (Cam Position Sensor) you may be able to keep your factory 258 stuff, or you might have to get a 4.0 wheel. If you get a CPS relocation kit from HESCO, you can keep the CJ 258 flywheel and starter, it will bolt right on to your 4.0. If you plan on using a CPS in the bellhousing, you need the flywheel and starter for a 4.0 as the CPS reads the tick marks off the 4.0 flywheel.
CPS Options
The two main options for your CPS are the HESCO relocation, and the factory. The HESCO is located herehttp://www.hesco.us/shop.asp?action=details&inventoryID=43098&catId=7902 or you can use a sensor in your bellhousing. If your bellhousing wasn't mated to a 4.0 from the factory, don't fear. Novak will drill up your bellhousing to be able to put in a factory CPS sensor for around $75-$100.
Cooling
Some more good news here. You can use a factory CJ 4.2 radiator for your cooling. Depending on what donor you get your 4.0 out of, yo may have an off-set fan. If your fan is off-set, you just need to get a wrangler water pump, fan, and fan clutch to center it all up. You can also use your factory CJ 4.2 radiator hoses
Wiring
Here is where everyone freaks out. It is daunting, but once you figure it out, it becomes second nature. It freaked me out at first, but once you have everything laid out it is not difficult. Their are only 5 wires on your Bulkhead that you really need to keep. They are the Check engine light, tach signal, ignition circuit, the fused battery ignition for the CJ fuse panel, and the starter relay. It's as simple as getting a factory manual for your particular harness and finding those wires. Make sure you get one for your exact year, as wiring changed a little every year that I have seen. You can then cut out all the other wires from the bulkhead and cut them off either where they go into a connector or where they go in to a splice. You need to find and splice a few wires in the CJ harness. They are 1.) 12volts from alternator to CJ fuse block (red)
2.) ignition crank wire (blue)
3.) ignition run wire (red with white stripe)
4.) fuel pump wire (not from CJ harness - you need to run this wire yourself based on what fuel pump set-up you use) You can also cut out any headlight wiring you may get. It doesn't really matter if you g e an auto or 5spd harness if you are 5spd. If youg et an auto harness you will just need to put the park sensor wire on a switch that you flip to make the jeep think you are in park or drive to crank. If you just ground this wire the computer will not receive a signal from the MAP sensor and will hardly move.
VSS(Vehicle Speed Sensor)
Their is a debate over if you need a VSS, I plan to get one. It will surely make your Jeep run better, and get better gas mileage. You need to get one with the electrical and mechanical hook up if you plan on using the CJ speedo. One from a 91 YJ will work, and from a late 80's Dodge Dakota.
Fuel Pump
You can do an in-tank, if you get a fuel sending unit from a TBI 4 banger YJ and the actual pump from a MPI 4.0. You will need to figure out wiring up the sending unit to make your gas gauge work, as it is exactly opposite of a CJ sender. You can also go external. That is my personal thought. Most guys that do the swap go with an External E2000 fuel pump. It was used in ford vehicles for many years. You need a pre-pump filter and post-pump filter. The pre-filter can be a standard filter, but the post needs to be a fuel injection rated filter. Also, you MUST have fuel injection rated hose where you use flex line. This stuff is several dollars per foot, but you need it to take the pressure. I also recommend fuel injection hose clamps for all connections. Ideally you need 5/16 line to the rail and for the return, but I think 1/4 on the return will work alright.
Ok guys, this is the gist of it. If I missed anything, feel free to reply asking questions, I will answer them to the best of my ability. This pertains to the OBD1 swap, as that is the one I have experience with. Let me know what you think, and if this should be a sticky.
Engine mounting
Well, their is some good news here. Your CJ 258 motor mounts will work. You do not need to move any mount brackets, or even change the actual mounts.
Flywheel/flexplate
Depending on how you plan to mount your CPS (Cam Position Sensor) you may be able to keep your factory 258 stuff, or you might have to get a 4.0 wheel. If you get a CPS relocation kit from HESCO, you can keep the CJ 258 flywheel and starter, it will bolt right on to your 4.0. If you plan on using a CPS in the bellhousing, you need the flywheel and starter for a 4.0 as the CPS reads the tick marks off the 4.0 flywheel.
CPS Options
The two main options for your CPS are the HESCO relocation, and the factory. The HESCO is located herehttp://www.hesco.us/shop.asp?action=details&inventoryID=43098&catId=7902 or you can use a sensor in your bellhousing. If your bellhousing wasn't mated to a 4.0 from the factory, don't fear. Novak will drill up your bellhousing to be able to put in a factory CPS sensor for around $75-$100.
Cooling
Some more good news here. You can use a factory CJ 4.2 radiator for your cooling. Depending on what donor you get your 4.0 out of, yo may have an off-set fan. If your fan is off-set, you just need to get a wrangler water pump, fan, and fan clutch to center it all up. You can also use your factory CJ 4.2 radiator hoses
Wiring
Here is where everyone freaks out. It is daunting, but once you figure it out, it becomes second nature. It freaked me out at first, but once you have everything laid out it is not difficult. Their are only 5 wires on your Bulkhead that you really need to keep. They are the Check engine light, tach signal, ignition circuit, the fused battery ignition for the CJ fuse panel, and the starter relay. It's as simple as getting a factory manual for your particular harness and finding those wires. Make sure you get one for your exact year, as wiring changed a little every year that I have seen. You can then cut out all the other wires from the bulkhead and cut them off either where they go into a connector or where they go in to a splice. You need to find and splice a few wires in the CJ harness. They are 1.) 12volts from alternator to CJ fuse block (red)
2.) ignition crank wire (blue)
3.) ignition run wire (red with white stripe)
4.) fuel pump wire (not from CJ harness - you need to run this wire yourself based on what fuel pump set-up you use) You can also cut out any headlight wiring you may get. It doesn't really matter if you g e an auto or 5spd harness if you are 5spd. If youg et an auto harness you will just need to put the park sensor wire on a switch that you flip to make the jeep think you are in park or drive to crank. If you just ground this wire the computer will not receive a signal from the MAP sensor and will hardly move.
VSS(Vehicle Speed Sensor)
Their is a debate over if you need a VSS, I plan to get one. It will surely make your Jeep run better, and get better gas mileage. You need to get one with the electrical and mechanical hook up if you plan on using the CJ speedo. One from a 91 YJ will work, and from a late 80's Dodge Dakota.
Fuel Pump
You can do an in-tank, if you get a fuel sending unit from a TBI 4 banger YJ and the actual pump from a MPI 4.0. You will need to figure out wiring up the sending unit to make your gas gauge work, as it is exactly opposite of a CJ sender. You can also go external. That is my personal thought. Most guys that do the swap go with an External E2000 fuel pump. It was used in ford vehicles for many years. You need a pre-pump filter and post-pump filter. The pre-filter can be a standard filter, but the post needs to be a fuel injection rated filter. Also, you MUST have fuel injection rated hose where you use flex line. This stuff is several dollars per foot, but you need it to take the pressure. I also recommend fuel injection hose clamps for all connections. Ideally you need 5/16 line to the rail and for the return, but I think 1/4 on the return will work alright.
Ok guys, this is the gist of it. If I missed anything, feel free to reply asking questions, I will answer them to the best of my ability. This pertains to the OBD1 swap, as that is the one I have experience with. Let me know what you think, and if this should be a sticky.