ford 4.0 ovh to 4.0 SOHC swap guide

marcytech

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Starting this thread for anyone interested in the swap
what this thread will cover: swapping a 4.0 SOHC engine into a OBD1 or OBD2 ranger/expo that has a 4.0 ohv engine. this swap uses the OBD1 OR OBD2 OHV engine wireharness, computer, and body harness.
whats the difference? almost double the horsepower and 50 ft lbs of tq at the wheels.
I had my computer tuned to help run the SOHC as best as possible, and before any adjustments were made we made note that the SOHC is completely safe to run on an old OBD1 or OBD2 OHV computer with a stock tune.
its a little fat on the top end but doesnt lean out anywhere
SOHC power output on original OHV tune was 165HP, 180TQ. (OHV power on same computer and in the same truck was 100 HP/139TQ)
*after a tune the SOHC put out 179HP/185TQ in a ranger with a C4, 35S and 5.13 gears.

first off lets start with mounting the engine into the truck.
1. trucks with heater boxes still in will need clearancing on the box for the passenger side valve cover.
2. engine mounts:
- the stock 4.0 ohv engine mounts will work for both 2wd. they will also work on 4wd frames but will need to be shimmed up a little bit. this can be done with a plate or washers inbetween the frame and bracket.
-Autofab 4.0 ohv engine mounts will also work and do not need to be shimmed
3. the transmission bell housing is the same aside from one of the top bolts.
4. the SOHC engine itself is a bit taller than the OHV, so if you have a cross tube on an engine cage youll want to watch for clearance issues

- ACCESSORIES.
1. steering pump.
-the OHV steering pump will not work. you will need to get a SOHC steering pump. this is good because its WAY quieter.
- custom lines for the steering pump will need to be made because the pump is in a different location than the old one.
2. alternator.
- the OHV alternator WILL bolt to the SOHC minus one bolt. you can build a bracket to accommodate the other missing bolt or leave it with 2 bolts. pulley location is perfect.
*note: you have to use the ohv alternator because of wiring.

3 Air conditioning: N/A for my application.

- FUEL DELIVERY
-your OBD1 ranger has a return style fuel rail. in order to use your existing fuel system for the SOHC you will need one of two things
*fuel rails from a 1997 explorer SOHC 4.0 (these are the only year sohc return style fuel rails.
OR
*new fuel pressure regulator that sends correct pressure to the fuel rail, and a return bypass back to the tank.
i went with the 1997 explorer fuel rails.
- you will use the SOHC injectors.

- WIRING
remember. you are putting a OBD2 controlled engine into a OBD1 environment. no sensor from the sohc will talk to the OBD1 computer
- injector wiring will be the same polarities and plugs between the ohv and sohc. so plug them in like normal.
-use the IAC off the OHV. it uses the same mounting surface and bolt holes on the SOHC just in a different location.
-use the old crank position sensor off the OHV. it bolts to the front of the block the exact same way.
-throttle position sensor is the same between the two engines. use either one.
-use your old OHV OBD1 MAF
- the OHV has a separate AIT (air intake temp sensor) and the SOHC has it integrated with the MAF. you will need to make a mount for the old IAT
* what i did was made a plug to block off the egr port on the SOHC intake and tapped the plug with 1/4" npt so the old AIT sensor threaded into the newly made plug (PIC BELOW)
- your OHV may or may not have a cam position sensor. this is the only sensor that will not transfer over. the SOHC has this sensor on the driver side valve cover. leave it bolted in so it doesnt leak, but no cam sensor will be used. the engine runs with out it. on the OBD1 system this sensor is only used to measure knock.
- you used the OHV alternator so that plugs in like normal
- temp sensors. you have 2. both are 3/8" npt thread. on the SOHC thermostat housing there will be spaces for two sensors as well, but one is a smaller thread. drill and tap it to accomodate your OHV sensors.
- oil pressure sensor is transfered from OHV to SOHC and uses the same thread pitch on the driver side of the block.
- ignition coil is exactly the same. use either one.

-MISC
youll need to get a sohc throttle cable, it mounts to the old pedal just fine.


IAT SENSOR PLUG
IAT snesor.jpg

old cps on new block
old CPS on new engine.jpg

missing bolt on alternator
c10ea01ffcc7bef71821eed7afa656a7.jpg
 
Thanks dude!

Lots of good information on this.

Swapping this motor to the 4wd frame. I (brian) had to notch the lower crossmember in order for the motor to fit. I'll add more information and pictures when the motor is out of the truck and the I start working on it again.
 
Alright I’m half way through this swap and running into some road blocks I hope someone will be able to assist me with. Here’s what I’m working with.

Sohc 4.0 out of a 2007 ranger. My original ohv was out of a 92 explorer. My sohc appears to have a completely different intake manifold than the one marcel has. That’s where I’m running into some issues.

When attempting to bolt the ohv IAC onto the sohc there is a clearance issue. I can fabricate a plate to raise it up enough to bolt on as long as that won’t cause an issue.

Second is the crank position sensor. Bolted the ohv unit onto the new motor and there’s a clearance issue there as well. The prong that sticks out is rubbing into the crank pulley.

for some reason my OHV alternator bolted up perfectly. All holes lined up unlike on marcels swap.

The throttle position sensor had a completely different plug than my ohv unit so I swapped the ohv tps onto the new motor. Bolted up fine hopefully everything is ok there

Last is the wiring. I see on marcels swap his injector plugs were correct for the sohc injectors. Mine are not. I assume I can swap injector plugs over from the other harness but I’m not sure which wire does what. I’d assume one is a power and the other is a ground. On the ohv harness there was a red wire and white wire going into each injector plug. On the sohc harness each injector plug had a larger white and yellow wire as well as a smaller multi color wire. Not sure how to wire these new plugs in correctly. Any help would be appreciated. This looked super strait foreword and now I’m running into issues.
 

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Here’s a pic of the motor as a whole to get an idea of which intake manifold I have
 

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Put your ohv harmonic balancer on that should fix the crank sensor issue.

As for the injector wiring I would look at harness diagrams to see which ones do what.
 
Put your ohv harmonic balancer on that should fix the crank sensor issue.

As for the injector wiring I would look at harness diagrams to see which ones do what.
Any idea for the iac? If I flip it around I can get it bolted up but the plug is facing up and won’t clear the hood. I can clearance the throttle body and it will bolt on like normal.

Also any idea why my swap is so much different? Possibly the year motor or the fact that it’s out of a ranger?
 
Any idea for the iac? If I flip it around I can get it bolted up but the plug is facing up and won’t clear the hood. I can clearance the throttle body and it will bolt on like normal.

Also any idea why my swap is so much different? Possibly the year motor or the fact that it’s out of a ranger?
you have the other type of intake. they made 2 types. also, get rid of the thermal stat housing. get a cast one. or you will be changing that thing about every year.
 
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Any idea for the iac? If I flip it around I can get it bolted up but the plug is facing up and won’t clear the hood. I can clearance the throttle body and it will bolt on like normal.

Also any idea why my swap is so much different? Possibly the year motor or the fact that it’s out of a ranger?

It’s not that much different other than the plugs for the injectors. That’s probably due to your engine being a tad newer than mine. If you can source the other intake manifold it’ll solve your iat issue. Or just clearance what you need to if it’s simple enough to do.

My buddy did the swap on a obd2 ranger and he too had to swap the injector plugs on the harness. I texted him asking about it but he doesn’t remember the wiring colors that he had. So no help there

Edit. I looked up injectors for a 1998 sohc out of an explorer and it looks like those use the same plugs as your original wire harness.
 

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Any idea for the iac? If I flip it around I can get it bolted up but the plug is facing up and won’t clear the hood. I can clearance the throttle body and it will bolt on like normal.

Also any idea why my swap is so much different? Possibly the year motor or the fact that it’s out of a ranger?

I have a 93 ranger EVTM manual with every single wire on a ranger in it. If you need any help with wires DM me

Edit: gonna throw this up, might help a bit. Can send more.

The S numbers mean splice
The C numbers mean connector
The G numbers mean ground
 

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Any idea for the iac? If I flip it around I can get it bolted up but the plug is facing up and won’t clear the hood. I can clearance the throttle body and it will bolt on like normal.

Also any idea why my swap is so much different? Possibly the year motor or the fact that it’s out of a ranger?
I’m Marcel buddy that’s also did the sohc swap. mine came out of a 08 ranger and went into a 96 ranger. So I had obd2 the swap was pretty easy and ran on my old ohv computer just fine.

So for my IAC I just used the one on the sohc motor and swap the connectors.

For your injector wires. I had to swap mine too.
My ohv harness was a big red wire and a smaller gray/white but that’s for clyinder 4

The sohc harness had red and brown/blue

I wanna say ohv harness has one main color and the other is different, I just found my older injector connectors. They right side is the red and the left is different I’ll show in pic
 

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I’m Marcel buddy that’s also did the sohc swap. mine came out of a 08 ranger and went into a 96 ranger. So I had obd2 the swap was pretty easy and ran on my old ohv computer just fine.

So for my IAC I just used the one on the sohc motor and swap the connectors.

For your injector wires. I had to swap mine too.
My ohv harness was a big red wire and a smaller gray/white but that’s for clyinder 4

The sohc harness had red and brown/blue

I wanna say ohv harness has one main color and the other is different, I just found my older injector connectors. They right side is the red and the left is different I’ll show in pic
on my OHV harness the wires going into the injectors are all the same. A red and a white/ yellow. On the SOHC injector plugs they all have a common tan/white wire and then a smaller multi color wire thats different on each plug. my question is which to connect where. I spliced the new connector in temporarily going white to white and red to multi color wire but im having second thoughts on if thats correct.

Ive read a few different forums that said it absolutely does not matter which way you wire an injector plug and a few forums that say it does matter.

good info on the IAC. As far as the issue with the crank position sensor goes, i believe that metal prong thats sticking out is just used as a reference point when using a timing light? in which case i could cut it down to clear the harmonic balancer? my ohv balancer is the same side as the sohc so swapping over wouldn't do me any good.
 
I wouldn’t use the sohc iac. John was able to because he was obd2 to begin with. Your obd1 computer probably won’t communicate with that newer sensor. But it would be worth a shot!

As for the injectors… You could always bench test each injector and see which side needs power for it to spray. Then look at the above wire diagrams to see which side is power and wire em accordingly! That way you know forsure
 
Yeah I was able to do some stuff different then Marcel since my ranger is a 97 and had obd2.

I wonder if that 98 explorer sohc has the same injector. Or if you could just run your ohv injector in it.

Have you tired to trace the wires back on the sohc harness and see if one color goes to each injector
 
made a bit of progress this afternoon. Traced wires back for injectors on both harnesses and confirmed i had it wired right. extended everything and got everything plugged in.

Was still waiting on my fuel pressure regulator to show up so decided to see if i could get it to fire up on a little squirt of gas down the intake. Got a few good backfires out the intake but nothing which leads to my next set of questions.

first things first i will confirm that the firing order if correct tomorrow. it has new plug wires on it from the previous owner so ill double check that they're all on correctly.

If they are correct my next suspicion would be some sort of issue with my crank position sensor? Im obviously getting spark and im definitely getting fuel since im spraying directly down the intake. So i am lead to believe im having an issue with the timing of the spark.

a few other things to note:

i am using the coil pack that came on the SOHC.

i currently have the throttle position sensor from the ohv bolted on. shouldn't make a difference in spark timing.

i currently have IAC from the ohv bolted to the throttle body but it is technically bolted on backwards at the moment to clear. shouldn't make a difference for spark timing.

i noticed one vacuum line that needs to be plugged. shouldn't matter for now.

and last i realized before i left that i didnt have the MAF hooked up. again shouldn't be contributing to the issue.

i will also note that im not terribly concerned that its a timing chain issue. I purchased this motor from a trusted person (OG DR member) who pulled it from his running truck. so for now i would like to rule out any timing chain issues these motors are notorious for.

i recieved my fuel pressure regulator this evening and will be installing it tomorrow to have a proper fuel system but would really like to try to figure this timing issue out before i fuck something up.
 
little update for anyone who will find this information helpful on their swap.

got the truck running. spark plug wires ended up being hooked up wrong causing the backfire out the intake. Found a misfire on #2, had good spark, had compression, and had power to the injector. decided to pull the injector to replace it and found that the injector sleeve was completely deteriorated and crumbling. Apparently, these motors use a plastic sleeve adapter into the motor and over time the plastic turns to mush.

decided to pull all the injectors to have them cleaned just to be safe, its cheap enough.

Also, worth mentioning I swapped over to the SOHC IAC and it seems to be working fine. I just swapped the plug to my old harness.
 
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