SOHC to OHV swap questions

[77'cj7]

EDIT: Since I never updated this thread, here's a synopsis of the final outcome. After the timing chains went, we performed the swap using the 98 Ranger engine, transmission, and ECU. The engine harness from a 99 OHV explorer was used. A return-less fuel sender assembly was added. Wiring changes were minor, I don't remember them all at this point; all the necessary info can be found in the applicable EVTM's. If you were to swap a sohc to ohv using a same-year donor, no wiring or fuel modifications would be necessary.

The truck has been running strong for over a year and 10k miles now, with no issues other than a exhaust manifold gasket leak. It now has a 4wd drivetrain, but the owner hasn't yet swapped in the 4wd front end parts. The final cost of the swap was just over $200, mostly fluids and gaskets.
Chris


OK, the premise of this project is absolutely as cheap as possible, I know there are many better options if money wasn't the problem.

Anyway, my roommate has a 97 SOHC 4 door 2wd with 225k and angry timing chains. We've decided fixing everything wrong in that motor would be a waste of time and money.

From my ranger v8 swap, I have a 98 ranger 4.0 ohv and 5r55e with less than 20k miles. Engine harness is hacked, but everything else is good. Also have ECU from that.

From the salvage yard, I have access to a 99 or 00 explorer OHV with toasted motor and trans. We already have the complete engine/trans harness and ECU.

Have the 98 ranger and 97 expo EVTM's, need to get the 99 exploder one.

PLAN: Drop the ranger engine and trans into the 97 exploder using the 99 explorer wiring and either the ranger or the 99 ECU.

The truck will be converted to 4x4 later if the swap works well. Already have manual 1354 from the ranger, so that wiring is not an issue.

Problems i've though of/ concerned about.
PATS, I believe the 99 expo will have pats, so i'd like to use the 98 ranger ECU. If this is impossible, is there any way to fool the ECU without swapping in the 99 column and module?

Fuel: assume I will have to swap the in-tank setup from the 99 into the 97.

Speedo, I know the 97 ex gets the speedo from the trans/t-case, and both the ranger and the 99 get it from the rear axle. Will there be a way to make the speedometer work? If not, owner is willing to use GPS as speedo.

General compatibility issues. I am very familiar with 5.0 swaps, however know as little as possible about the 4.0's. Has anyone mixed and matched these systems, and what is required? Are the body plugs the same? Will the ranger ECU play nice with the explorer harness?

Sorry for the long post, but I feel detailed explanation is necessary.
Thanks,
Chris

 

[mr cribb]

I have never heard of going backwards with motors. The SOHC was more powerful than the OHV.

For speedo, why not put in the rear axle from the 99? It'd make things easier I think.

 

[77'cj7]

I know the SOHC to OHV swap has been completed many times, I'm just not sure on this specific version.

The axles in the 97 and 99 are already the same, the vehicle just reads the sensor differently.

 

[BigPip]

I own a 98 Explorer that came factory with a SOHC engine. Somewhere in its life someone put in a OHV engine.

yes, my truck does run and it runs good but it does come at a cost. Since I have owned this truck I have found that there are only 3 differences in the ECM between the SOHC and the OHV, 1 of which is the way the camshaft sensor is ready which gives me a problem every day. It takes for ever to start then it sputters for a few.

Another difference is the exhaust, SOHC has 2 cats and 4 O2 sensors, OHV has 1 cat and 3 sensorts ( 1 on each bank before they merge and 1 after the cat). I am not sure if you want your A/C but that mounts differently as well...

Power- when you put your foot down, it has immediate power then it goes away for a few hundred RPM then it amazingly comes back.

Exhaust manifolds are different and the exhaust will have to be re worked from the manifolds to the CATS.

I have confirmed that I am still running on the SOHC ecm, if they put another ecm in I believe they would have had problems with the PATS system and they left well enough alone.

Besides the hard starting, surging in power I have a loud and annoying exhaust leak that I have already fixed 2 weeks ago.

Unless you plan on switching the ecm, wiring harness and exhaust system, you are going to have some problems. TRUST ME-

I have purchased a SOHC engine that I have already tore down and i am about to start rebuilding it, if i can't find a donor V8 Explorer/mountaineer soon. I used to do all my shopping at rockauto.com but I have found if you search around using the parts number, you can find a good deal around.
The timing set (cloyes 90398SA) I have found for $284 where rock wants $334.

 

[77'cj7]

Wow, I'm really surprised it runs at all. Both of the ECM's i'm considering are OHV specific, one from a 98 ranger and one from a 99 sploder. If I can get the Ranger ECM to work, I will be completely skipping PATS, so thats the current plan. I still have the ranger's Y-pipe and custom hi-flow cat setup, so i'll be able to splice that into the sploder exhaust easily enough.
Also, It's definitely worth waiting for the right V8 donor, its a way better setup. In my case, however, we're trying to pull off the whole swap for a couple hundred bucks at most.
Thanks,
Chris

 

[BigPip]

Well, I have some positive news reguarding the swap.But first, lets talk about your computer issue, if you change computers you will have a problem with the PATS, your key has a chip in it that must match the Pats module and match the Computer.

With my MUTT, as I call it, the main problem I have had was the harness for the engine only plugged 3 o2 sensors. The truck and current computer has 4 so bank2 sensor 2 was not hooked up. This weekend I ran some wiring down to the 4th o2 sensor, studied the hell out of the factory computer pin harness wire diagram and I connected it to the computer! So far it is running SO MUCH better, night and day difference, and I have only pulled 2 different codes. One was p0113 which after I erased it Sunday night has not came back and today I got a 171 which is an o2 code on bank 1- NO CODE FOR BANK 2- MY WIRING WAS COMPLETELY SUCCESSFUL!!! The engine they installed in my truck was out of a 99 which is fantastic news becuase the cam sensor in 99 wires up to the same pin as the SOHC engine does. The OHV in 98 and previous were different, I planned on re running the Cam sensor wires to where they needed to go to match the SOHC computer but after many wiring diagrams and studing, I found I got luck.

Truck is running on SOHC computer and it is running really good. Today I hooked up my trailer to it and I plan on towing about 1000lbs of steel behind it. I am sure if I will have a problem, it will be today.

I am slowly changing my thoughts of the SOHC swap to an OHV... if I can get the engine light off...

 

[BigPip]

So far the only codes I get are 171, 174 and an occasional IAC code ( i forgot the number, I haven't seen it for a couple of weeks but I know it is bad). I looked into my coolant overflow tank and it was EMPTY! I am hopeful this confirms the theory of bad intake gaskets along with the hard start and missing for the first few moments.

I ordered a new intake gasket set from RockAuto, it looks like it included everything. Lets see what happens next.

 

[mr cribb]

The one thing I didn't like w/ fords SOHC theory was the timing chains... in any engine not just the 4.0, kind of a pain to do and heaven help you if you're off one tooth.

My dad destroyed a 4.6 this way.... he showed me the #3 piston.... there was bits n pieces left.

 

[BigPip]

I have a smooth idle again! This morning I replaced the IAC before work, what a difference ideling at 11-1200rpm rather than the 400-500 I have been. Filled up this morning and only 15mpg but I had a trailer behind the ole ex for about 100 of those miles. I hope to replace intake gaskets next weekend to improve the hard starts and chocking at about 2500rpm and the bank 1&2 lean codes.

 

[LSCR351]

Good luck on that intake gasket thing. Every 4.0 OHV I have worked on with those simptoms has turned out to be a small crack in the head.

 

[BigPip]

I am about to get started on on it. Lets see how it goes.

 

[LSCR351]

Well?

 

[BigPip]

installed new gaskets, everything went pretty well. Still have lean bank 1 & 2. did some more digging and found out that when they installed the wiring harness, they plugged the 3rd O2 sensor into bank 2 sensor 2 which should have been bank 1 sensor 2. I also found out that when I wired in the sensor for 2/2 I put in into the harness 2 pins over so I wasn't getting a reading off that sensor. These were fixed on Tuesday. Drove it to work on Wednesday and I was down to only bank 1 lean. Went home to pull both front o2 sensors to switch them to see if it followed the sensor. After I switched them, i plugged in the scanner just to find out I had both banks lean, I should have checked before going through all that work.

I am having a problem with fuel pressure so until I get that figured out I believe I will continue to run lean. that's a project for next weekend.

i will say, since the intake gasket, the truck does have more low end power, amazing the difference. Could be I had the battery disconnected all day but none the less, more low end power. Still hard starts and no power at WOT. I did spray inside the intake via, pcv valve, and it cranked right up, NO hesitation.

 

[BigPip]

fuel pressure is 58...
So, now whats next, I was counting on low fuel pressure for the solution of my problems... that didn't work.

 

[snoranger]

fuel pressure is 58...
So, now whats next, I was counting on low fuel pressure for the solution of my problems... that didn't work.

Ok, just making sure I got this straight.

Youre running a 99 OHV on a 98 SOHC computer.
You've got lean bank 1 + 2 codes.
The O2 sensors and intake gaskets didnt solve the lean codes.

Did you know the SOHC uses 24lb injectors and the OHV uses 19lb injectors?

If your computer thinks its spraying fuel from a 24lb injector and its really spraying from 19lb the engine is going to run lean.
You can try one of two things:
Replace the injectors with 24lb'ers or find a 19lb calibrated mass air meter from an OHV.
One of those should work.

 

[BigPip]

Ok, just making sure I got this straight.

Youre running a 99 OHV on a 98 SOHC computer.
You've got lean bank 1 + 2 codes.
The O2 sensors and intake gaskets didnt solve the lean codes..

Correct but I did not change the O2 sensors but switched sides. For a moment there it looked like I was only getting a 171 code but at the last minute I picked up a 174 also.

Did you know the SOHC uses 24lb injectors and the OHV uses 19lb injectors?

If your computer thinks its spraying fuel from a 24lb injector and its really spraying from 19lb the engine is going to run lean.
You can try one of two things:
Replace the injectors with 24lb'ers or find a 19lb calibrated mass air meter from an OHV.
One of those should work.

This is good to know! It is currently running the MAF from the OHV engine, I had thought about converting it over to the SoHc MAF and Air Temp but when I checked the readings for these two, there were right where they needed to be according to factory specs.

I did find that this engine requires 56-72psi of fuel pressure and I know when I was reving the engine (in park in driveway) I was getting down to 56 psi. I am sure at WOT I am dipping below the 56 psi so I don't think I should rule out the fuel pump just yet. At 1/2 to 3/4 throttle this thing runs great!

 

[snoranger]

I would smoke test it and make sure there are no more vacuum leaks before I go replacing any parts.


Thats easy for me to say, I own a smoke machine.

 

[BigPip]

Quick update, I found that I was mistaken earlier when I thought I was running a return system... I am not. The truck is setup to run a return system and I even found the return line lying around the engine compartment. I just purchased a fuel rail from a 98 EX with a return system on it and today I ordered brand new injectors so I can get that settled.

new injectors should be in by Friday so I will install the new stuff on sunday.

 

[BigPip]

SOHC to OHV

Finally, I did it! There was A LOT to learn and take in but I have finally done it! My truck is a 98 SOHC with a '99 OHV engine running on a '98 SOHC ECM.

Here are the juicy details as I had to approach them, the OHV was already in the truck when I bought it-

Wiring-
On the 99 OHV engine, everything plugged in perfectly and nothing had to be modified, just one thing added (B2S2 O2 sensor) on the 98 and prior years, the Cam Sensor is wired differently and I thought I was having problems with it but after comparing a wire diagram from a 99 OHV, the 98 OHV and the 98 SOHC I found that they changed the way it was wired working out most beneficial for this swap! '98 and prior would require minor adjustment to just one of the wires.

Now lets talk o2 sensor, the OHV motors only had 3 sensors so the wiring from the engine will only have 3. The 2 upstream sensors stay on the same bank and the 3rd sensor will go to Bank1 behind the cat. I had an extra wire harness so I clipped the wires for the Bank2 Sensor2 O2 and I had to run them up to the computer where I manually plugged it in the the computer using a tiny drill bit to open the port and I soldered a new tip on it from my spare wire harness so it plugged in exactly like it would factory.

Exhaust-
Use the SOHC factory exhaust to ensure the 4 O2 sensors can be used. The down pipes from the OHV will have to be welded to the SOHC exhaust. I have to have mine redone because mine are not right and keep leaking.

FUEL-
This has been my BIGGEST PITA for the project! Hard starts (5-10 seconds of steady cranking), NO power at WOT and hesitation and it goes on. In 99 these trucks went to 'RETURN-LESS' systems but in 98 and prior they had a return system. Both running at completely different fuel pressures. The engine (99) was never changed to a return system. Today I was able to install brand new injectors with a 98 OHV fuel rail WITH the return line.

*Note- on a return less system, the supply line is on the front of the fuel rail on the fuel damper. On a return system, the supply is towards the back and the return is on the pressure regulator in the front of the engine. I didn't know this ahead of time and I had to buy fuel lines again today at the junkyard.

Anyways, after I figured that out and hooked everything up, AGAIN, it fired right up and ran great. For the first time, it has POWER at WOT!

The only other thing I can think of is the cruise control cable needs to be switched out and I am running the same 5-speed automatic that came with the truck.

To 77'cj7, I retract my first response and tell you to give it a whirl!

I want to thank everyone who has chimed in to offer advise and I am glad I am able to give back, I hope this someone else out there.

 

[BigPip]

All this time and money spent to find this today:



Nice, huh?