Alright guys, So I have all but decided to buy the 5.8 liter engine from my buddy's 1991 bronco, that car has the E4OD trans in it. My truck is a 1994 5.0 f150 and I believe it has the mazda M5OD manual trans in it. The bronco engine is in good condition and they are giving me the entire assembly, from the belt to the bellhousing. I will get the distributor, pumps and pulleys and even the wiring harness. I need to know a few things and I hope you can help. First, I know I need a new flywheel, I have been told that the engine should mount to my manual trans but that I will need the flywheel from the 5.8. Will the current car have the correct flywheel or do I need to buy one specifically for a manual trans? will I also need a new flexplate and clutch? or will my flex plate and clutch from the 5.0 work with the new flywheel. Second I have been told that the engines will have different ECU or PCM components, I cannot afford to buy the ECU of of these guys, or at least I can't right this second. Will this completely prevent the vehicle from running? (I just need to get the thing running, it does not have to be perfect by any means, but I don't want to damage anything). Third are the wiring harnesses going to be different? I have heard that there is some debate over MAF versus some other system, I am less familiar with these components of the trucks and I am learning as I go. Finally is there anything huge and glaring that I have forgotten?

Thanks all,

M

 

Yes you need a different flywheel, it's not about size or offset it's just that the two engines have a different balance, but you can use the clutch you have. Flexplates are for automatic transmissions and not applicable here.
You cannot use any wiring that comes with the 5.8, all of it has to be removed from the motor and only the engine harness that was originally in your truck can be used.
I suspect your '91 engine has a distributor with an ignition module on it, the '94 truck will have used a system with a remote mounted ignition module, all that means the wiring at the distributor is different. To deal with this you need to either buy an early 5.8 distributor with a module on the side and swap on a steel drive gear to match the steel roller cam in this motor, or modify the distributor that comes with the engine to accept module. This isn't terribly hard you just have to drill a few holes and change the internal pickup module, and these parts could be salvaged from the 5.0 distributor you have. No you can't just use the 5.0 distributor because these two engines have different shaft sizes.
That is it other than making sure the spark plugs are routed for the 351/HO firing order, the motor will run on the existing 5.0 PCM you have.

 

Thanks for the Quick response, All very assuring. could you give me a little more instruction on the distributor wiring?. Since I am replacing the entire engine with the 5.8's distributor from the donor vehicle, why would I have to replace any part of the distributor? is this a mechanical or an electronic issue?

 

It's a wiring issue that requires some mechanical changes to solve. The distributor wiring connector on your truck now won't plug into the distributor on the 5.8, and you can't just change the connector. This is a problem because the ignition modules are in different locations on the 2 vehicle and the best solution is to modify the distributor so that the wiring stays intact.

 

Wouldn't' the easiest thing be pick up a 94 5.8 distributor & take the known cast iron gear off the 91 donor 5.8 distributor & put on the new?

Although when I got one of the current china knock offs recently for mine [94 5.8], it listed as NOT being roller capable (steel gear)

 

Oh rats I got the dates reversed... '91 engine going into a '94 truck I thought it was the other way around. Well it is till the same problem and yes the easiest solution would be to buy a newer distributor but it's really not much work to modify the existing if every dollar matters.

 

gotcha, so I gan simply buy a new distributor gear and slap it on? will it run prior to that and thats just a good idea to replace? or is that something that needs to be done before I even try to start it up? Also can you give any more details about the flywheel I have been doing a bunch of research, should my current clutch and pressure plate mount up to a 28 oz flywheel if I bought a new one. Want to make sure I can just buy the flywheel and that I don't need to buy a new pressure plate, bolts, clutch etc. Goal is simply to get it to run and drive as a back up vehicle It is not going to be driven hard or driven often. Once I have time and money and space I can begin the more tedious modifications.

 

would you possibly be willing to give me a run down on how to modify the module? Sounds like the newer trucks have steel gears and remote mounted ignition modules (i remember pulling this off and learning about it in the disassembly process.) and the older engines have cast Iron gears and the ignition module is mounted on the distributor? Besides changing the gear, what modifications need to be made to the distributor?

 

You can google "remote mounting ICM" & come up with the procedure. There are aftermarket suppliers who make a harness, but they are geared to the Fox Mustang. (works, but you still have to hack it)

It's possible to open up the harness & lengthen it, but it is pretty tedious & creates a lot of possible failure points if not familiar with it.

But truly you can get a knock off (there are NO NOS or service replacement or rebuilt Motorcraft) distributors for under $150.

You can get a parts house cast iron gear for under $10, but I'd take the one off the 91 distributor rather than trust an aftermarket gear.

Then everything is plug & run.

 

Might as well ask this as well. I busted the male end of the pigtail for the 5.0 distributor a while back trying to remove it. One of the pins broke off. Will I need the pigtail from the donor engine (I am getting the wiring harness for it anyways). Secondly It sounds like the cam gear change is unnecessary if I keep the donor engine's distributor in it. The PCM on my current vehicle wouldn't run the donor Pickup Module? or am I getting something backwards. Also I think both vehicles are Speed Density so that should make things a little easier. I am getting the full motor from intake to oil pan pretty much and I am planning on transplanting as much of it as I can at one time without taking off too many pieces.

 

I kinda goofed on the part of what you were asking. The remote conversion I mentioned above is not the thing you need. The idea is to hook straight up existing wiring from the 5.0 to the 5.8 distributor.

The ICM ignition control module Is grey & is on the distributor of the 91 5.8 The ICM is on the fender of the truck is black & the wiring is not a direct connect because they are different internal wirings too as well as connectors.

You might be able to convert the PIP wiring internal to the 91, but I can't tell you straight out how. I can send you a stub connector out of my spares maybe if you have no junk yard easily available.

I

 

OK the difference is in how the wiring harness is attached to the pickup module inside the distributor.
On the 5.8 motor you are getting it is through the TFI module mounted on the outside of the distributor, there are 3 pins that connect these two devices through a slot in the distributor body.
On your '94 truck the TFI module is remotely mounted, so there is a wiring harness that comes directly out of the distributor with a short pigtail with a round connector.

These distributors can be completely disassembled after the drive gear is removed, the shaft will pull out and then the pickup module inside can be removed. These pickup modules are the same regardless of motor so you can take the one from your 5.0 distributor and put it in the 5.8 copy, you just have to drill/cut a hole on the side of the distributor body for the harness to come through. You will see the size and shape of this hole when you dismantle the 5.0 distributor, just copy that in the 5.8 version, the body is aluminum so it is easy to drill or cut with simple hand tools if that is all you have.

 

I'll gladly defer to you on this. I thought there was a difference between the 3 pin connection on the dist. mount & the 4 pin harness connector on the remote mount. (edit, 4/14, 5-pin)

The aftermarket/big box Chinese distributors come with a cover on the underside of the flat ICM flange so they can be outfitted as either style.

 

There is and that is why the internal pickup module has to be changed.

 

I think I understand where you are going with it now. I do remember some of the pieces you are describing from when I took apart the 5.0 dist. to replace the ignition pickup coil, if fact I bought a new one and will use that. Regarding that round pigtail, I do remember breaking a pin off of the male end of the connector which comes from the wiring harness and connects to the distributor. I'm assuming I will need a new one unless there is a way to fix this. Any ideas where I might find a new one? maybe the junkyard? Also it sounds like I will use the ignition pickup module from the 5.0 truck not the 1991 system from the donor engine?