1994 302 to 351w swap
04-07-2016, 04:54 PM
#1
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1994 302 to 351w swap
Hello, I bought a 351w motor,harness and ecu.
We rebuilt it, pulled the 302 and dropped the 351 in. With the 351 ecu it ran but wouldn't shift, put the 302 ecu in and it runs and shifts but seems to lack the power I'd expect. The truck has a 4R70W tranny, I just can't figure out the engine/tranny/ecu combo. Any ideas? I just ordered a ecu for a 351w and c6 tranny from eBay, that didn't work either. Can the ecu be reprogrammed for the 351 or the 351 ecu for the new tranny?
We rebuilt it, pulled the 302 and dropped the 351 in. With the 351 ecu it ran but wouldn't shift, put the 302 ecu in and it runs and shifts but seems to lack the power I'd expect. The truck has a 4R70W tranny, I just can't figure out the engine/tranny/ecu combo. Any ideas? I just ordered a ecu for a 351w and c6 tranny from eBay, that didn't work either. Can the ecu be reprogrammed for the 351 or the 351 ecu for the new tranny?
04-09-2016, 01:22 PM
#2
Senior Member
The 351 with the original 302 cpu should work - it might just take a little bit of time for the computer to "learn"
Also you aren't going to feel a tremendous difference in power from a 351. I think they are rated very simliarly hp-wise.
Also you aren't going to feel a tremendous difference in power from a 351. I think they are rated very simliarly hp-wise.
04-12-2016, 03:25 PM
#3
The 351 ECU was probably for a 351 / E4OD combo which would be why it didn't shift. You would need a 351 / 4R70W ECU. But I'm not sure you could get a 351 in 94 with MAF which I would assume you have.
In 94, the 302 may not have had the HO cam, it wasn't standard until 95, so that would make your injectors fire wrong, which could account for the loss of power. Unless the 302 did have the HO cam in which case what BLD truth said will work eventually once the computer learns.
If the 94 302 wasn't HO (check the firing order sticker on the rad saddle) then you would most likely need a custom ECM. A 95 302 / 4R70W one might work.
In 94, the 302 may not have had the HO cam, it wasn't standard until 95, so that would make your injectors fire wrong, which could account for the loss of power. Unless the 302 did have the HO cam in which case what BLD truth said will work eventually once the computer learns.
If the 94 302 wasn't HO (check the firing order sticker on the rad saddle) then you would most likely need a custom ECM. A 95 302 / 4R70W one might work.
04-15-2016, 05:52 PM
#4
Senior Member
acceleration won't be much more, but towing is quite different. 351 is much more of a truck engine in my opinion, but empty the 351 only accelerates slightly faster.
04-15-2016, 05:52 PM
#5
Senior Member
The 351 ECU was probably for a 351 / E4OD combo which would be why it didn't shift. You would need a 351 / 4R70W ECU. But I'm not sure you could get a 351 in 94 with MAF which I would assume you have. In 94, the 302 may not have had the HO cam, it wasn't standard until 95, so that would make your injectors fire wrong, which could account for the loss of power. Unless the 302 did have the HO cam in which case what BLD truth said will work eventually once the computer learns. If the 94 302 wasn't HO (check the firing order sticker on the rad saddle) then you would most likely need a custom ECM. A 95 302 / 4R70W one might work.
