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302EFI to 351EFI swap Computer Solution

4773 Views 3 Replies 3 Participants Last post by  urban_cowboy
For all you who are looking at upgrading, here is my story. I have spent the last month working on getting my 302EFI swapped to a 351EFI. After much deliberation, I decided to go with a complete kit from Jasper. The 351EFI package included injection system, block, computer, and most everything else excluding accessories like the water pump, fuel pump, AC, and Alternator. The total advertised horsepower of this kit is around 330hp. My shop spoke with Jasper about what we were trying to do and they recommended this package, so we got it on order.

After pulling the old 302 and installing the new 351, we ran into some small issues integrating the existing fuel line into the provided injection rail and lines. This was easy enough to fix by simply using a new rail from a 351. The next problem took us a month to line out. After installing the 351 we began to run into computer and wiring harness issues. The computer provided was a Ford factory computer that was modified by Jasper. When we began trying to integrate the sensors for emmisions into the Jasper computer, we ran into a problem. Jasper could not get us the wiring diagram for the computer and after much try and error, the computer would run the motor but not let us get past 2800rpm. Jasper R&D departement did not help us much on this and could not get us any information we needed to integrate this kit into a EFI truck. We then decided to go with a Ford factory 351 computer which would not be programmed for my performance cam and heads. We knew this option would come at some performance/efficiency cost, but we has little choice. At this point we just wanted easy and we knew the factory computer and wiring harness could be installed with a little modification for the Jasper ignition system. After much research, we found that Ford no longer makes or sells computers for the earily 351 EFI motors. We were able to find a replacement that seems to work. We had to unhook the check engine light due to some inputs that were not being used on the Ford computer. The unused inputs were creating an error, so this was the easiest solution.

I drove it for the first time yesterday, and the motor runs pretty well. I believe there is a little performance loss, but it is still much better than a stock 351EFI. I have not had it on a dyno, so I have no real horsepower numbers, but my gut tells me about 260-270hp at the rear wheels. The performance cam that came with the kit does not like normal low idle speeds, so we had to bump up the RPMs to keep things smooth. i think we are currently running at about 1200 out of gear and 900 in gear. All in all this was a pretty good kit. After futher reflection and experience, this kit is really indended for carb to EFI conversion due to the lack of computer inputs for emission sensors. In hindsight, I would probably go with a performance long block from Jasper and simply build out the injection and ignition systems from aftermarket parts. If anyone is thinking of making the 302 to 351 swap, consider going with a completly stock 351. This would be the cheapest and easiest solution. If you are like me and wanted more, consider building out your complete system from a good base performance long block. I still have a high opinion of Jasper, but they really led use a stray on getting this kit. My guess is we came out about the same on parts as a complete build out, but the labor and research was much more. In fact, I estimate it took us 3 weeks longer to do it the way we did.

Good luck on your swap outs and death to the 302s!
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Sounds like Jasper SUCKS in the tech/help department, at least on these issues. If you already had a 302 why did you bother with a new harness? You could've used the 302 harness, and I definitely would've went with an original 351 Ford EEC from the start. EEc modified by Jasper screams "problems" to me. Well at least you got it taken care of now, let us know when you get all the bugs worked out.
I'm convinced when the time comes to move from my 302 to a 351

I'm just gonna drive down to Lansing MI and buy Fireguy's whole setup right out of his truck and stick it in mine right there ! I'll give him enough so he can take a cab until his new $h!t arrives by UPS

Wishful thinking'

We did end up using the factory wiring harness (my mistake), and I agree that we should have used a Ford EEC to begin with. The reasoning for not doing that was the Ford EEC for the '88 is not programmed for my performance cam and heads and cannot be modified very easily. It was our impression that the Jasper computer was tuned specificaly for this package, so we wanted to utilize it if we could.

Now I just need to get my tranny working a little better and get a few bugs out of the idle.

I agree that buying fireguy's system would be a good way to go. You would think that upgrading from a 302 to 351 would be something most good engine shops and engine manufactuers would know by heart. Jasper is a good company and make quality products, but their Tech Support blows and their R&D dept must be one big FILE 13!
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