There's going to be a lot of differences between engines that are four years apart, but not as insurmountable as the changes all manufacturers went through from '95 to '96. I assume these are both 5.0L engines. There are some Chryslers where you can switch engine sizes and use the same hardware and computers, but for all other brands, don't even think about changing to a different size.
For physical things, I use the Rock Auto web site for reference a lot. If a part has the same part number for both years, you'll know they're the same. If the numbers are different, you'll know they're different but you won't know why, unless you can tell from the pictures. First of all, you can be pretty sure the exhaust manifolds are going to be different. You can use the original manifolds on the new engine, but only if the bolt locations haven't been changed.
You have to look at how the injectors and spark plugs are timed. When that is done with notches in the flex plate, it is real common for the number and spacing of those notches to change from one year to the next, so you have to keep the original flex plate with the vehicle. Same with vibration dampers on GM engines. Also look at the locations and sizes of the radiator hoses, power steering hoses, and AC hoses. You'll likely have to switch mounting brackets on the front of the engine.
One thing that is almost always overlooked is the profile of the camshaft lobes. Valve lift, duration, and timing sets the "personality" of the engine. That's what allowed Chrysler to use their 225 c.I. Six cylinder in a two ton dump truck or a motor home, AND it was sufficient for highway speeds in cars. Your truck engine will likely have a slightly retarded camshaft relative to the Explorer camshaft. Late valve timing produces increased low-end torque. That's what gets a motor home going from a stop sign and a pickup truck gets going with a trailer. Your Explorer is likely to have a slightly advanced camshaft timing. That provides so-so get up and go, but much improved high-end torque for passing other cars and going up hills.
The shape of the lobes affects emissions too although I'm not an expert in the specifics. Fuel volume will self-adjust right away if necessary, but how far and how quickly the valves open affects how and when the fuel enters the cylinders. That can leave some fuel hanging up in the intake manifold or "puddling" on the back of cold intake valve faces. That puddling can cause severe hesitations or stumbling, mostly when the engine is still cold, but if it occurs there, it will occur to some extent all the time and result in increased emissions from unburned hydrocarbons, and reduced fuel mileage.
Ford was pretty consistent with their sensors during this time period, but you'll still want to double-check that both engines use the same part numbers. Throttle position sensors have two different orientations of their connector terminals, but as long as you can plug the connector into it, they both will develop the same signal voltages.
On all car brands except Chrysler products, the mass air flow sensor is the main input for fuel metering calculations, so that is the one that could be different. Now you have to wonder if it is tailored to the camshaft profile and timing, or to the weight of the truck. This is one variable you might have to experiment with, and there are likely to be others.
Wednesday, February 11th, 2015 AT 12:53 AM