I have a 1996 f150 with a 5.0 that's got a knock and low compression in one cylinder. I bought a 1996 5.8w to swap in knowing they are both mass air engines and that the old harness will work(I'm partial to plug and play). I am just stumped on finding a flex plate to use. I know its specific to the 5.8 and trans combo. So my question is what can with a 5.8/4r70w combo? I can only think of a bronco of about the same year being possible but I'm not sure.

 

It may be hard to believe but nothing came from the factory with a 5.8 and 4R70w, but all is not lost because they did put an 351 with an AOD back in the mid 80s and those 2 trans use the same flexplate so that is what you need to buy.

Did that 5.8 come from an F150 or Bronco? If not then it's not from a mass air truck and even worse it wasn't OBD2 either so the wiring on it is no good to you. But you should never use any wiring that comes with a donor motor anyway. In your case the OBD2 system added some unique components like the crank misfire sensor and the DPFE EGR system and the killer is you can't transfer either of these from the 5.0 because the EGR tube is shaped differently and connects to a different place and the crank balancers have different weights on these two motors.
Hopefully you have an OBD2 motor and don't need to deal with this.

 

The 5.8 is complete with all the sensors and cut harness. So I can change the connectors if needed and the whole egr system is there too. The engine is out of a 96 e150 which u thought shared all if the same driveline components as the trucks but now I'm not sure. So that engine/trans combo came from a late 80's f250 correct?

 

Yes the 1/2 ton E-series had the same drivetrain as the F series but if the harness is cut then don't waste a second messing with it just remove the upper intake and disconnect everything right on the motor, and then reconnect your original 5.0 engine harness portion once the new motor is installed in the truck.

The 351/AOD combo was used in mid '80s Crown Vics actually.

 

I wasn't planning on using any of the 5.8 harness unless I came across a plug that was different. And thank you for the info on what flex plate I need. My one last question is why do j keep seeing people saying to pull the upper intake off?is it easier to pull the engine and place the engine without it or is there another reason?

 

Yes it's easier to install the motor with the upper removed, and it's necessary to disconnect the wiring.

 

Thank you everyone for the info. I have to wait a month or so to but exhaust pieces I'll need but I will keep you updated with how it goes.

 

get shorty headers and install them prior to dropping in the motor. you will also need a 5.8 y pipe as your 5.0 y is to narrow.

you can find the necessary flexplate from an 88-90 crownvictoria 5.8/AOD, thats the info the parts store will need.

otherwise everything should be straitforward.

 

one last question after more then 6 months later....what is the difference does the flex plate make? I mean why are they weighed differently if they are for the same engine? The donor engine plate weighs 24oz. and the crown vic that you said i should use is 28.2oz. forgive me if i'm wrong but wouldn't i also need to change the harmonic balancer also if i changed the flexplate?

 

the 5.8 has a 28oz imbalance. you need the crownvic flexplate so it bolts to the torque converter correctly. Using the wrong flexplate for the wrong trans could be fatal for the trans.

the weight is important obviously. 5.0 = 50oz imbalance / 5.8 = 28oz imbalance.

 

i don't mean to be a nuisence or seem like i'm not understanding but why do i find that the 5.8 that i am using had a stock flex plate imbalance of 24oz

 

Not sure where you got "24" ounces from. Once upon a time, all Windsor small block engines used 28 ounce imbalance flywheel/flexplates, crankshafts, and harmonic balancers. Balanced as a set. Then around 1981 Ford decided the smaller 302/5.0 engine should be imbalanced at 50 ounces but the 351W/5.8 engines would remain with 28 ounces.
People learned pretty quickly that you didn't put a 28 ounce flywheel on a 50 ounce engine or vice-versa. They'd fit and bolt up but the engine would shake like a wet dog. Enough to be a little scary.
I swapped a 1996 E250 5.8 into my 1994 F150 5.0 4R70W truck. Asked the parts guy for a 1991 Crown Victoria 5.8 (police car) flexplate.
The only wiring issue I ran into on mine was the 5.0's knock sensor was in the top rear of the engine block while the 5.8 had it in the intake. No big deal, only two little wires.
I did have some issues with fitting the air injection system which I basically ignored and didn't hook up. In some states I know you couldn't get away with that. If my donor had been a truck instead of a van it might not have been an issue. I've never bothered to look into it though.

 

It doesn't so wherever you are getting that info is wrong... simple as that.

 

the engine i used for the swap was complete with all sensors from the throttle body to oil pan and serpentine belt to the flexplate.
i already have the stock flexplate for the engine (1996 E150). i was trying to find out why i needed the flexplate from a crown vic if i already had the correct one for the engine.

i was at both napa and advance auto and they both told me that the stock flexplate was 24oz.

 

If you have the flexplate from a 1996 E150 5.8 then it's for an E4OD transmission. This means it's correct in all ways except the offset and you DON"T have the correct one for your engine AND transmission combination. The offset is small but you can see it if you place an AOD/AODE/4R70W flexplate face down on a flat surface next to a C6/E4OD/4R100 flexplate. And it's important. I've had to replace a broken transmission pump for a guy who thought an E4OD flexplate would work in just such a situation where he actually needed an AOD flexplate. Just like you do, because you don't have the right one yet.
I mean do what you want, but I like swapping in 351W's so I've been there and done that like six times now. I think Conanski lives, eats, and breathes Ford engines. I don't know what else to tell you. The $7.50 an hour (what Advance pays around here) parts counter guys might not be your best references on this stuff.
There's two guys, Tom Monroe and George Reid, who have written some excellent books about small block Ford engines. They both have excellent reviews and their books are very well thought of references by most Ford fans.