hey guys, I'm just wondering if anyone has ever dropped a 4.0L from a ranger into a 1988 f150. I can pick up a complete ranger (minus the front clip) from a friend of mine for nothing. The ranger is the same year. I want to make the truck to get better mileage and I'm not worried about power I just need to get from A to B a little cheeper then the V8.

 

Considering the 4.0 is pushing around a lighter truck, I'd say you would get worse mileage.

 

I'd be willing to bet that your gas mileage won't improve much with the 4.0 because that's a bit underpowered to move that much truck.
I'm soon to start a 91 explorer project and it has the 4.0, I know the engine and radiator mounts have to change to drop a V8 in the explorer/ranger frame, so I would think you'd have to fabricate those in doing the visa versa version because I highly doubt that anyone makes a kit to downgrade to a 4.0 in an F150.
If you want better gas mileage, a tune up, checking all your sensors and ignition upgrade/timing bump will go a lot further than you'd imagine. Not knocking your idea, but my F150 has the 4.9 and I couldn't see good results from anything smaller than that. Now dropping in an I6 wouldn't be a bad idea, but the only reason I'd suggest a route other than the 4.0 swap is 1) it's gonna be a lotta hassle to lose power 2) that gas mileage is really gonna suck being so underpowered 3) you'd probably have to buy a new driveshaft because the 4.0 DS is shorter than an F150s

 

... and the F150 DS may not be right for the 4.0 tranny, not to mention the crossmember may need to move forward since the 4.0 is shorter it'll probably move your tranny forward, i.e. need an obscenely long DS. Then you've gotta worry about driveshaft wobble as well.
All in all, the idea isn't a bad one (the part about improving MPG) but the 4.0 is not how you're gonna get what you're looking for. I get right @ 20MPG with the I6 bone stock, no upgrades. If you're thinking in the 30MPG range, then you just ruled out most any full sized truck

 

Even the new hybrids are only rated at like 21city/21hwy from chevy

 

Besides a 4.0 is a dis system so you would have to figure spark and timing, you would have to get the complete wiring harness, but on the plus side, 4.0 is mass air.

 

But you can convert your current engine to mass air for not too much...

 

I have a 07 f150 4x4 for all my truck stuff and my 4 banger car for all my commuting. the 1988 is more of my toy its slammed but I don't drive it much because its just a lot of truck to be just out driving around. right now the truck is tuned up and its got a home made cai, headers, no cats, flowmaster. everything to do with the ignition system is new and I have been running all kinds of fuel additives and engine cleaners through it when I was driving it. its just getting really hard to justify pointless driving with these gas prices.
As far as the install goes I could be getting a complete ranger with a messed up frame so all the wires would be there. for the motor mounts I'm a millwright working in a welding shop so the resources are there if I need them.

what is the mass air system? what kind of mpg are most people getting on their older f150s?

 

Pointless driving is the American way dude.

It being a play thing, I say go ahead and try it. It would be neat, different. I put a fuel injected 3.1 in my S10 Blazer that had a carbureted 2.8, where most people would have dropped in a 350.

 

If I get the ranger I might go ahead and do it. I have more plans for that ranger then just the motor idea so why not if I have it . I'm no longer a fan of doing whats been done and expensive bolt on kits. I traded a 89 YJ that I dropped a 350 in for this old ford and I have no plans to part with this truck.