Opportunity to Upgrade to SOHC

[mechjames]

I have an opportunity to get a friend's SOHC engine from a 98 Explorer that was crashed. It was rammed into the passengers side, and after hitting the inertia switch, the motor started up great and didn't seem to have any timing chain rattle at all. It has 240,000km. Mine has 298,000km and I found a chunk of something in the oil pan, so I have to pull my motor to find out what it is, and I also need to change the rear main seal.

Until this opportunity showed up. I've seen some threads of some people who have attempted this swap. What I have found out is,

-The SOHC will run on the OHV computer if you spend a lot of time splicing the SOHC wiring connectors into the OHV harness
-By doing this, you can keep the A4LD with the 3-4 shift and overdrive.
-You have to modify the heater box to make room for the SOHC valve covers
-Air conditioning can be retained if you take the lines out of the SOHC truck.
-Since it is a early SOHC, the intake manifold is a return system, so it will work with my fuel line setup from the OHV.

But would the EEC-IV give me the mileage and power of the SOHC with an A4LD transmission? Instead of OBD-II with the later model transmission?

Am I correct in the above?

Now since I would pretty much have unlimited access to this truck for wiring, why don't I:

-Pull the whole harness and computer and convert to OBD-II
-This would mean I would have to use the SOHC transmission because the OBD-II can't shift the A4LD 3-4 and O/D, and would probably throw codes for 1, 2, and 3 because the solenoids wouldn't be there
-Would the new transmission hook up to my transfer case alright?
-And if I did a bit of wiring I could make the OBD-II work with my stock first gen dash (like tach)
-And with 2nd gen having air bags, and 1st gen doesn't, would this cause any issues?

The deciding factor will be what is found in my oil pan (I had the oil tested @ Blackstone and Aluminum spiked during that OCI). It only has 50,000km less then my motor now. How reliable are the SOHC's in their high mileage years? Maybe there would be more SOHC's at the wrecker in the future if I do this swap later.

I have 2 weeks to decide. Chime in with your thoughts.

 

[mechjames]

No replies? Someone out there must know the answers!

I'm probably going to pull my motor this weekend to find out if it's damaged or not. Then I need to make the decision.

 

[snoranger]

Until this opportunity showed up. I've seen some threads of some people who have attempted this swap. What I have found out is,

-The SOHC will run on the OHV computer if you spend a lot of time splicing the SOHC wiring connectors into the OHV harness
-By doing this, you can keep the A4LD with the 3-4 shift and overdrive.
-You have to modify the heater box to make room for the SOHC valve covers
-Air conditioning can be retained if you take the lines out of the SOHC truck.
-Since it is a early SOHC, the intake manifold is a return system, so it will work with my fuel line setup from the OHV.

But would the EEC-IV give me the mileage and power of the SOHC with an A4LD transmission? Instead of OBD-II with the later model transmission?

Am I correct in the above?

Yes, the engine will work with the early computer. (see my sig)
I cant tell you about fuel mileage with a A4LD, I'm using a 4r55e and a 95 comp. I'm getting about 18 MPG mixed city and highway. I defiantly have more power then an OHV, I've owned a few. Dont know what a SOHC running on a OBD-II computer feels like, I never owned one.

Personally, mine runs good. I drive it 60 miles round trip to work everyday. But this will be my last SOHC that I own. I'm not happy about the timing chain issues with this motor. I know that there are many of them that have gone quite a few miles, but It seems that Ford has not really found a fix, they just put a few band-aids on it. Look how long it was in the Mustang, 4 years and out. Its no longer in the Explorer and they were supposed to stop making the Ranger by now. Seems like Ford will never look for a fix for these issues, they had just planned to stop using the motor.

Sorry, rant over.

 

[2000StreetRod]

VIS & knock sensor

Some of the 98 SOHC V6 engines have a variable intake system. The length of the intake runners start changing around 3000 rpm for better performance.

All of the SOHC V6 engines have knock sensors. The PCM can advance the ignition timing at least 2 degrees and retard the timing at least 8 degrees based on inputs from the knock sensor.

Without the SOHC V6 PCM you will not have either of the above capabilities.

It's my opinion that upgrading your 94 OHV to a SOHC is more trouble than it's worth. You will encounter numerous time consuming little problems that will prevent you from using your vehicle. If you want the additional power of the SOHC, just do the minimum to keep your OHV running, buy a 2nd generation Explorer with bad timing chains and swap the bad engine with your friend's good one. Ford has still not reinforced the traction side of the rear guide assembly with metal. Mine broke off at 150,000 miles and I had to pull the engine to replace the cassette.

 

[snoranger]

Some of the 98 SOHC V6 engines have a variable intake system. The length of the intake runners start changing around 3000 rpm for better performance.

All of the SOHC V6 engines have knock sensors. The PCM can advance the ignition timing at least 2 degrees and retard the timing at least 8 degrees based on inputs from the knock sensor.

Without the SOHC V6 PCM you will not have either of the above capabilities.

It's my opinion that upgrading your 94 OHV to a SOHC is more trouble than it's worth. You will encounter numerous time consuming little problems that will prevent you from using your vehicle. If you want the additional power of the SOHC, just do the minimum to keep your OHV running, buy a 2nd generation Explorer with bad timing chains and swap the bad engine with your friend's good one. Ford has still not reinforced the traction side of the rear guide assembly with metal. Mine broke off at 150,000 miles and I had to pull the engine to replace the cassette.

Dale

Everytime someone asks about running the SOHC on the OHV comp you bring up the knock sensor. I've said it before and I'll say it again. It will work, dont use the knock sensor and run higher octane gas. I run 89 octane and drive the truck like its a rental. I've yet to have any problems with preignition.

The simple fix for the variable intake is to use a newer upper intake without the variable runners. If your dead set on using the variable runners there are ways to make it work. Off the top of my head--- I could use a MSD rpm switch to turn on a relay. Relay to open a solenoid and allow vacuum to flow to to variable runner, thus opening the different length runner at whatever rpm I want. It may be a pricey way to do it, but it should work. ( just looked up some prices, I could have that set-up working for about $75. Not bad.)

You seem dead set in your mindset that it wont work. It does work. If you'd like to see it working come to Jackson, NJ and you can look it over and take it for a ride.


To the OP:
I wouldnt be swapping in a SOHC with mileage that high.

 

[2000StreetRod]

Wasn't doubting your word

Dale

Everytime someone asks about running the SOHC on the OHV comp you bring up the knock sensor. I've said it before and I'll say it again. It will work, dont use the knock sensor and run higher octane gas. I run 89 octane and drive the truck like its a rental. I've yet to have any problems with preignition.

I wasn't doubting your word that you can run the SOHC with the OHV PCM. And you're correct that the knock sensor is not required. I was just trying to point out one of the designed capabilities that won't be available. As a matter of fact, I have been having trouble with my knock sensor causing the timing to be retarded 8 degrees at WOT since I purchased my Sport. I have two different custom tunes (disabled and enabled knock sensor) to work around the problem until I get it fixed.

The simple fix for the variable intake is to use a newer upper intake without the variable runners. If your dead set on using the variable runners there are ways to make it work. Off the top of my head--- I could use a MSD rpm switch to turn on a relay. Relay to open a solenoid and allow vacuum to flow to to variable runner, thus opening the different length runner at whatever rpm I want. It may be a pricey way to do it, but it should work. ( just looked up some prices, I could have that set-up working for about $75. Not bad.)

Once again I was just pointing out something to consider. Ford apparently decided that the VIS performance improvement wasn't worth the cost to retain it. I assume that is why it was dropped for the 99 and later engines. I suspect the carbon builds up in the control mechanism due to lack of use by socker Moms and quicks working. You're absolutely correct about using a MSD RPM switch. I bought one used on eBay for $35 and a used vacuum switch for $15 in case I decided to try the earlier manifold. Ford changed the 98 PCM VIS control pin to the fuel cap open sensor connection on later PCMs.

You seem dead set in your mindset that it wont work. It does work. If you'd like to see it working come to Jackson, NJ and you can look it over and take it for a ride.

Not true. I believe that it does work and I admire your accomplishment in overcoming the technical challenges to make it work. But how long did it take you? And don't you agree that there will be even more problems with swapping to a 94 chassis? Retaining the OBD-I diagnostics would be simpler than switching to OBD-II but OBD-II is much easier to use with expanded capabilities.

To the OP:
I wouldnt be swapping in a SOHC with mileage that high.

I agree that an engine with that mileage is cause for concern. I encourage anyone who has a SOHC engine out of the bay to at least take the time to pull the valve covers and inspect the upper section of the timing chain guides before reinstalling.

 

[snoranger]

Hey Dale, sorry about the little rant. I had just got done arguing with the wife.


To the OP:
If I were to do it again, I would swap to OBDII and get a custum tune to eliminate the extra stuff that the OBDII truck doesnt have (fuel tank sensor, downstream O2 sensor, Etc). The only reasons I did the OHV computer is because:

1--I have $650 into the entire project. That includes buying both trucks.
2--The SOHC engine was WELL under 100k miles.
3--The OBDII engine harness was destroyed in the accident.
4--I wanted to see if it worked, it worked so well it became my Daily Driver.

 

[2000StreetRod]

EGR differences

I believe the 94 has a PFE sensor (voltage output proportional to 1 port monitored) for EGR while the 98 has a DPFE sensor (voltage output proportional to the difference between the 2 ports monitored). However, there may not be any significant difference in the sensor output sent to the PCM.

One significant advantage of OBD-II is the remote custom tune capability.