There have already been some great threads on doing the 351 swap like here 302 to EFI351 swap
and here 302FI-351w FI swap
Below are some of the details specific to a 1996 302 to 351 swap in California. The engine change process would apply to all smog controlled vehicles in CA so I hope it can also help others for other years too. Thanks again to Fireguy50 for providing me with much of this information.
1. No smog pump on the 1996 351.
There was not one in 1996 (there is on '96 302s though) and this made things harder.
According to CA law, you have to use an engine of the same year as your vehicle or newer, have all the smog equipment from the donor engine and the host chassis. Additionally, the donor engine has the come from a vehicle from your vehicles GVW class. So, no 460s from F-250s or F-350s in your bronco. For more information, see the engine changes guidelines from the CA BAR
I followed the rules but many manuals and diagrams show there is a smog pump on this engine. This is probably because the earlier years had smog pump and the diagrams and info were "carry overs". The smog referee station included. I was initially failed. They would not even accept a picture of the Vehicles Emissions Label from the donor truck. Only after I provided a letter from Ford Motor Co. (not a dealer letter) stating that the 1996 bronco 351 did not have a smog pump did it pass the visual inspection.
2. 1996 351 computer.
I had to have this also. The 302 computer threw code(s) and the check engine light was on. I had the 351 computer so I used it and it was fine. I never read the codes from the 302 computer but I thought it could have to do with the 302 computer looking for the smog pump. Note that the smog ref also asked if I had the 351 computer.
3. Exhaust crossover pipe.
The 1996 351 and 302 had the extra sensor than previous years. The 302 crossover pipe is too narrow to use with the 351 and the 351 pipe is $1600 new from Ford! You can weld a bung in a previous year head pipe and add the O2 sensor, but obviously if you can grab the pipe from the donor that's the way to go.
4. Wiring harness.
The 351 wiring harness does not have the connections for the O2 sensors. I heard that for some weird reason they hook up at the tranny on 351 trucks but I never confirmed this. You will need to use your 302 wiring harness. Note that you will have the connection for the smog pump that you no longer need though. You may also have to lengthen a couple of the connections, like the one to the EGR.
5. The smog referee.
You will need to make an appointment with the DMV smog referee to get your vehicle registered with the new motor.
When you call to make an appointment, tell them it is for an "engine change". Otherwise, there may be confusion if you use terminology or vernacular they are unfamiliar with like "motor swap". Note that they could actually treat it two different ways: either an 1) engine change or 2) engine replacement. They classified mine as the latter since the 351 was a factory option.
When you go to the smog ref, make sure you are on time as they are usually pretty busy. Make sure that you follow all the normal smog test practices like 1) plenty of oil and water in your truck 2) have your vehicle registration 3) have the money to pay for the test and certificate 3) your check engine light is NOT on (automatic fail) and 4) adequate air in your tires for the dyno test.
They may not ask you any questions at all, but be prepared to point out where the EGR, charcoal cannister, PCV and other smog parts are on your truck as well as the location of your obd-ii access port. The refs are nice people but remember that they have a job to do and need to check everything. Plus, they see all types of vehicles and cannot be expected to know where everything is on each one.
When you pass, they will place a new sticker in your door jamb. It will include your VIN, the emissions equipment on the new motor, the new motor size and the date. You will need to point this out to smog test stations for future tests.
, if you ask was the swap worth it? The answer is yes. I was hoping it would be, but was cautiously optimistic. Now, with the roughly 50 ft-lbs more of torque, the truck has much better take off acceleration, allows hill climbs to be done with more confidence and allows the engine to hold highway speeds without the auto tranny hunting back and forth between 3rd and 4th.