okay here we go again.
OBD-II has nothing to do withthe OHV 4.0L engine, jsut the computer that controls it.
they did not change much during the OHV's life, except for the sensors and intakes, but the engine blocks are the same.
So you can use any year of the OHV in your truck, as long as you swap your intakes and sensors to the new one.
here is everything you need to know, copied from Doug's post in the other thread:
Well, being that it is a OHV to OHV swap it's pretty straight foward like before mentioned but there are a few differences that can confuse a simple guy.
1) The intake studs in the fuel rail are longer because the plastic intake is thicker the the aluminum one, this really doesn't matter except for the front stud, you have to put the nut on the stud before you put the throttle cable bracket back on.
2) The CMP drive and/or sensor. All 95-00 will have this and use it,the 91-94 4.0's either won't have it OR you will have a different style. If you older truck doesn't have it then I wouldn't even take it off the block, it doesnt hurt anything sitting there.
3) All of the sensors, and don't forget the crank sensor in all of this. The temp sensors in the front of the intake must be swapped as well and finally all of the wiring harness from the vehicle it is going in must be used. Like before mentioned their won't be a low oil level sensor on a 98 and newer 4.0 so you'll either have to swap pans or not worry about it and let the wire hang, or tie it up out of the way. I think I would know before the oil level got low enough to trip this light anyway so I wouldn't worry with it.
4) The Exhaust manifolds must be used from the older Explorer but there too they bolt right up. On a 98 and newer there will be exhaust studs that must be removed from the heads, they won't work in the early model exhaust manifolds.
5) Upper intake and possibly fuel rail if your using a 98up returnless system. You can use the new injectors, don't remove them but the rail itself must be changed. Also the 96-up OHV's have a plastic spacer plate below the fuel rail and you must reuse this plate between the lower intake and fuel rail or the injectors will bind up and you'll get an vacuum leak because of the difference in height.
6) Finally the flywheel on a 98up are 8 bolts, you can use the new style flywheel on the old style transmissions no matter whether it's an auto or manual. Now if you have a C4 behind it that's a whole different ball game but I doubt anyone else has ran into this problem, if you do I have a special made flywheel lying around .
That's all I can think of right off hand but it's a very straight foward swap. It's the same basic long block just the heads are different. The exhaust ports on the 98up's will be smaller then your old ones but dont worry with that on a stock setup.
One important thing to remember is you can go late model to early model but you can't go early model to late. The reason being is the number of engine mount bolts on the side of the blocks. They used new castings for new bolt locations every couple of years and it's very specific on that. The way this goes is pretty much...
91-94 used one bolt setup
95-97 another
98-00 the final
You can use the 98-00 on any year model but the 95-97 can only go back, not foward.
Thanks, Doug904
