I have a 1991 Explorer XL with the 4.0L V6, but the cylinder heads are EXTREMELY rusty... So bad that the spark plugs have fused with their threads, and won't come loose (even after a couple weeks of soaking with PB Blaster and Breakfree). In fact, the #1 plug is broken out, and now has an E-Z Out in there, that also broke in an attempt to remove the stuck plug housing.

The bolts holding the heads to the engine are in much the same condition, so replacing just the heads looks to be more bother than the vehicle is worth. I'm concidering replacing the whole engine, but unfortunately I can't seem to find any running 4.0L that are even remotely local, and my budget is somewhat limited this summer.

The question I am asking is this. What other Ford engines (out of Rangers, Bronco II's, etc.) are interchangeable with the Gen 1 Exploders? I'd like to get it roadworthy again, but don't have the space in my garage to do much modification to get something to fit, otherwise I'd just put a V8 in there.

The truck still runs, and is actually driveable, even concidering the E-Z out is all that's in the #1 plug's opening (not far enough in to damage the piston, fortunately) but I can't really drive it around with it not firing on all cyl., now can I? It seems a shame to not fix it, since the rest of the vehicle is in pretty good shape.

Any other ideas on what I might do with this little beast, other than just selling the whole thing outright, would be greatly appreciated as well.

 

I think any '90 to '94 4.0 (whether from a Ranger or an Aerostar) use the exact same long block.

A 2.9 L from an '86-'92 Ranger/BII should be an easy swap, if you get the wiring harness and such. I don't know why you'd want to put a smaller engine in there, but it would fit in your Explorer. Because the 2.9 went out of production after '92, I don't see it being easier to find than a 4.0.

I'm not sure what modification needs to go into putting a 2nd gen 4.0 OHV in. I know the 2nd gen OHV has a higher compression ratio, but I don't know that it would require any body/frame modification to fit in there. It might mostly be about getting the accessories/engine management wiring figured out. If you get it to work with the '94 engine management, you might have to use higher octane gas so it doesn't ping because of the higher compression ratio.

I've heard of a couple of people who have put a 2nd gen SOHC into a 1st gen, but I don't know that it's any easier than putting a 5.0 in, and you might also run into transmission issues if you have an A4LD, as I don't know that the A4LD would hold up well to the SOHC.

 

Well, pulling it out of the garage today, I blew the rear brake line... It's turning out to be more trouble than I can really work with right now, so I'll most likely wind up selling it off, or parting it out.

Thanks for the reply, shorty. I really feel disappointed that this thing is worse off than I had thought, but I suppose since it didn't cost me much to begin with, I'm not really out a lot of cash.

If anyone happens to want a '91 Xploder with good interior (minus the door handles) and a fair body, let me know. It currently DOES run, even with the broken spark plug in the #1 cyl., and the ruptured rear brake line. Trans shifts firm, 4x4 works well. The hood and rear hatch have some bad rust, but I already have new body panels to replace them, and even in the same color as the truck was already.

I'm in the QC area of Iowa, and will let this thing go for cheap. I just want it out of my garage. I can snap some pics of it possibly tomorrow, and will try to post them on here.