i have been searching for a while on 302-351 swaps. i find a lot of info but not what i need. i am ready to pull my hair out. sorry for the long post. here is my situation. i have a 1995 f150 XL 4X4. i am pretty sure it is a 4r70 trans. the pan is square with 1 hump in the center. i thought i was a e4od until today. my mechanic has never done a 302-351 swap before. he is my cousin and gave me a good deal on the labor cost. he said it would be no problem. so i purchased an atk 351w from napa. found an old 351 in a junkyard to return for the core deposit. used the valve covers, oil pan, fly wheel, oil takeup, and intake off the junk motor. had them cooked and cleaned before install. got a new dist, harmonic balancer, plugs, wires, belt, etc. a couple days ago we put it all together, put it in the truck. used the wire harness for my old 302, and 302 computer(could not find a 351 ecm). the truck started and ran. found a ecm today. junkyard said it was the right one. plugged it in and the truck would not start. after disconecting/reconecting the battery and trying to start several times, we put the 302 computer back in. the truck started right up. it is running rich and the right side seems to be loading up with fuel. there is raw fuel dripping out of the bottom of the header, and last night there was a small fire for a second or two come out of the header. would this be from the 302 ecm, bad injectors, vacum leaks? also the oxygen sensor is not installed in the header yet(not sure if that would matter). is the 351 ecm i got today bad or the wrong one? everything i read on swaps, guys were pulling the motor out form a junk yard or other truck and were taking the harness and computer from the same truck. how do i find out what ecm i need for my truck? we told the person at the yard my make, model, 4x4, autotrans. does it have to do with the vin #'s? also i read tonight on another forum that there is not a computer out there for a 351 that will work with the 4r70 trans. they said you have to get a "standalone computer" to control the trans. is this true? any hekp would be appreciated
thank you------------blip

 

The 351 Computer will not work with:
1. the 4R70W Transmission.
2. any injectors except #1 & #2.
3. MAF sensor.

It would be hard to start the engine with two injectors working, no input from the MAP sensor.

In short the 351 uses bank injection and the 302 uses sequential.
The 351 uses a map sensor and the 302 uses an MAF sensor.
The 302 computer will work an E4OD & 4R70W transmissions.
The 351 Computer will only work the E4OD transmission.
There are one or two more differences but you get the idea.

 

basically you are saying the computer is probably good, so hold on to it. so what would i need to do? can i just change out the maf to a map or is it more involved than that? if i change to a map sensor will this solve the injector problem. i may be misunderstanding about the 351 computer not working with the injectors, could you elaborate a little more please? i may be able to get a e40d transmission. thank you for the much needed info.

 

Read below NO, read below In 1995 the 302 (5.0) computer (PCM) has eight pins (wires in the harness) to fire each injector (sequential firing) in the firing order.
The 351 PCM (computer) has two pins (wires in the harness) to fire the eight injectors (bank firing).

The PCM uses different pins (wires in the harness) for some of the operations in the E4OD and the 4R70W transmissions.

In short you would need all of the wiring harness from the 351 including the one that goes from the dash to the transmission for the E4OD and the 351 to work with the 351 PCM.

What you have now if all of the sensors and actuators are working right should work with the 351, 4R70W transmission and 302 PCM. I am not sure what you would do with the knock sensor wires.
The 302 and 351 had the same firing order in 1995.