Engine Swaps In California

[L.A.X]

I have a 91 Explorer with the 4.0 OHV engine, I believe. While the engine runs and idles good, it is in need of a refurbish. I'm at the point of either rebuilding my current block or pulling a good block from the Pick A Part and rebuilding that one. Was thinking about a V8 but due to smog issues and red tape in California, maybe a 4.0 would be best. I believe that I am allowed to swap in an engine size that was available for my year, correct? Is the SOHC superior to the OHV or vice versa. If I pull a 4.0 from the yard, what year would be my best option??

 

[Anime]

You can legally swap in an engne that is from a model year newer than your vehicle (even a V8), but swapping in another 4.0L V6 (or rebuilding the one you have) is going to be a lot easier.

The SOHC has slightly more HP, torque, and mileage, but has its own set of issues with the design, mostly in dealing with the timing chains and other maintainance items that aren't as easy as the OHV.

I'd see what motors you can find. You can swap in a 4.0L OHV from most any Explorer, but you'd also need to swap over lots of other stuff, especially the ECU, wiring, etc.

Rebulding may be a better option. You can get new aftermarket heads to fix the issues with weak heads on the 91-92 and 93-94's, new rockers, pushrods, etc.etc. Depending on the condition, you might not have to completely tear it apart, and can just fix issues, replace gaskets, and have an engine that's ready to go hundreds of thousands more miles.

 

[L.A.X]

You can legally swap in an engne that is from a model year newer than your vehicle (even a V8), but swapping in another 4.0L V6 (or rebuilding the one you have) is going to be a lot easier.

The SOHC has slightly more HP, torque, and mileage, but has its own set of issues with the design, mostly in dealing with the timing chains and other maintainance items that aren't as easy as the OHV.

I'd see what motors you can find. You can swap in a 4.0L OHV from most any Explorer, but you'd also need to swap over lots of other stuff, especially the ECU, wiring, etc.

Rebulding may be a better option. You can get new aftermarket heads to fix the issues with weak heads on the 91-92 and 93-94's, new rockers, pushrods, etc.etc. Depending on the condition, you might not have to completely tear it apart, and can just fix issues, replace gaskets, and have an engine that's ready to go hundreds of thousands more miles.

I would much rather rebuild this block if the bottom end is in good condition. I wont know the status until I start tearing it apart. My truck runs ok currently but motor seems tired. I'm also debating on whether to do it myself or take to a shop for the rebuild.

 

[L.A.X]

I found this link on the differences between the 4.0 engine types.

http://www.samarins.com/glossary/dohc.html

 

[Anime]

Here's an article about the differences between years of the 4.0L OHV V6:

http://www.therangerstation.com/tech_library/40rebuild.htm


You can spend a few hundred $$$ on things like new gaskets, heads, rockers, and generally take care of all the known issues with the motor, and get it back to top shape without a complete rebuild, if it has no other problems. You also save the hassle of compatibility issues that come with getting one slightly different motor to work correctly, just remove, repair, replace, and bolt it back in and you're good.

Throwing in a K&N filter or FRAM Airhog can let the engine breathe easier, and you can put on an aftermarket cat-back exhaust (or just a muffler) and get more HP, torque, and driveability. I highly recommend the Dynomax Super Turbo muffler.

The fuel pumps can wear out, and the fuel filters do need to be changed, so a new fuel pump and filter can add some pep as well.

 

[Travisfab]

For how cheap Explorers are, and especially damaged ones, a V8 is a no brainer for me. Just get the whole truck.

 

[L.A.X]

For how cheap Explorers are, and especially damaged ones, a V8 is a no brainer for me. Just get the whole truck.

I love my truck and want to get it back to the way she shined on the showroom or close to it

 

[L.A.X]

Finally got around to getting quotes for a complete engine rebuild. The shop I found in my area is giving me a quote of 2000 for the complete rebuild and 600 for the install. They gave me a two week or less timetable.

This is what the company does in the engine rebuilding process:
complete engine disassembly
(pistons, rings, bearings, timing chains, plugs and other parts are discarded)
thermal and or chemical cleaning
(engine block, cylinder heads, cranks, cams)
engine block crack inspection
(Visual and/or Magnaflux)
crankshaft reconditioning
(Grinding and Micro Polishing)
boring and honing of cylinders
connecting rods are inspected and replaced with new or rebuilt ones as required
block resurfacing as required
assembly to precision OEM Specs
in-house remanufacturing of cylinder heads
new or remanufactured rocker arm assembly

 

[L.A.X]

Parts that are replaced:

new main and connecting rod bearings
new pistons and wrist pins
new piston rings
new cam bearings
new timing components
new freeze plugs
new or rebuilt oil pump
gaskets – full set

What do you guys think?

 

[Anime]

I'd be wary of engine "rebuilders" that just do the same thing for any engine with mystery or no-name parts.

Particular engines have particular issues, and just throwing a bunch of cheap parts together on an original block might sound good to some people, but it's not how to do a proper rebuild.

The 4.0L engine, the 91-92 in particular, has weak 90TM heads from the factory.

A proper rebuild of this motor involves new heads, new rocker arms (or preferably new rocker arm assemblies from Ford), new pushrods, cleaning and restoring the lifters, and a lot of other things.

I also don't see any need to just throw out the original pistons for new aftermarket ones unless there is an issue with them at inspection. Note that many, many times, even with high mileage, the 4.0L OHV block, the cylinder walls in particular, have very, very little wear, if the oil was changed regularly. Even if the block is bored just for the heck of it, just stepping up a piston ring size is all that is needed.

I'd also be wary of a place that specs "new or rebuilt oil pump" - which says to me they are going to use the cheapest rebuilt they can get and don't really care much about how important an oil pump is to the life of a motor.

There are a LOT of cheap, cheap, cheap low quality parts out there. Throwing them on a motor for a "rebuild" can result in an assembly of junk that might look pretty at first, but will not last like the factory stuff.

Know what you're getting. Ask what brand names of parts an engine rebuilder uses. Ask about head replacement and where they'd source the heads. Ask about what brand of gaskets they use. Ask about mileage warranty and what's covered.

I'd steer clear of any place that just sources a cheap "rebuild kit" of parts and gaskets from China, and throws the stuff on a motor, oblivious to the particulars of that engine.

I'd also tell any place that rebuilds the motor to save all of the old parts and give them back to me. This lets you inspect them yourself, and also keep any good ones in case whatever parts they used fail and should be replaced with the originals.

 

[Travisfab]

I love my truck and want to get it back to the way she shined on the showroom or close to it

Me too. I'm saying instead of messing with a rebuild, find a T-boned 5.0 and swap the motor and harness.

 

[STEWARTW]

Could you perhaps better define what you mean by "tired"? If you have good compression and your not burning oil it seems punching it out to just punch it out may not gain you anything. That thing is 20 YEARS OLD. Any number of things could be affecting performance. Of the multiple high mileage OHV 4.0's I've had apart I've usually been shocked how little wear there was on cranks and cylinder walls and such. I'm talking visual and mic measurements.

 

[Jason94sport]

We already tried to tell him that before.....

Throw the newer heads on, rocker assemblies, & head gaskets & call it a day

 

[L.A.X]

We already tried to tell him that before.....

Throw the newer heads on, rocker assemblies, & head gaskets & call it a day

Took it apart, gonna go your route and call it a day. Thanks for the great advice

 

[vq5speed]

There's no red tape in doing an engine swap. Unless you want to create trouble for yourself that no one cares about.. You can swap any 4.0 OHV short block into your 91 without changing the ECU. Just use your intake manifold and other stuff off your engine put it on the swapped 4.0. I did it with a 95 long block. I used the heads on the 95 but used my manifold and other stuff. The 4.0 OHV engine was still available up to 2000. In 97 is when they came out with the SOHC but still offered the OHV engine. If you swapped for a SOHC block then you will need to change the ECU and everything else that goes with that. I don't know if its been done swapping to a SOHC engine but would like to know myself whats needed to do it. I am thinking of doing another short block swap as my rings are going bad. I don't need heads as I have new heads already been done. I would look for a low mileage OHV 4.0

 

[mr cribb]

There was a thread I followed last year. I think his screen name was rjcooper396ss or something like that.

Anyway he has or had a 2nd gen v6 to v8 swap and it is CA legal, CARB certified and all.