OK, so I want to build a 351W and put it into my truck. I have spent months even years considering and researching and I think that was worse than actually just doing it because it has been hours spent sifting through loads of conflicting information.

I could really use someone (who has actually carried out this swap) to disspell the rumors and "I think" information.

- Does the 302 wiring harness work on the 351?
- Does the EEC need to be replaced with one coded for the engine/trans/location information, or will a 302 box run a 351 engine?
-If so, where can I get info on what EEC model number I need?
-What accessories (i.e. alt/water pump etc.) r swappable?

 

All depends on what year your working with. If the 302 is MAF, yes it will work, i did it in my silver 95. But if its an older SD 302, you will need to change computers.

 

It isnt MAF, its a '91. I guess what I am missing there if the 351 was offered in the same year it would seem to me that a 351 could be built for speed density. I should also note that I am not against converting to MAF but I am looking for the path of least resistance.

how about that engine harness/parts?

 

I JUST finished swapping a '92 5.8L into my '95 F-150 w/ MAF 5.0. The only thing I had to change on the 5.8 was the distributor as the '92 had a dizzy mounted TFI and my '95 pickup has the remote mount on the driver's fender. New remote mount dizzy was around $80 and plugged right in. You'll have to modify your exhaust as the deck height of the 5.8 is taller and your 5.0 exhaust will not bolt right up. Everything else dropped right in. I even swapped all my known good 5.0 accessories over to the 5.8 block. You need to run a longer serp belt than the one on your 5.0 as the increased deck height of the 5.8 spaces the acc farther apart (I used one for an E series van w/ 5.8L app as I run the van saginaw power steering pump/ bracket). I also have a 4R70W tranny thats computer controlled & the EEC has taken the 5.8 swap just fine (I did not change trannies). You'll also need the appropriate 5.8 flexplate or flywheel for your application as the 5.0 is 50oz imbalance and the 5.8 is 28oz imbalance.

Any more questions pop up feel free to shoot me a message as its all still very fresh in my head.

Fungus

 

Thanks Fungus, good information...and I am sure once the fun begins more questions will pop up!

 

If you want to keep the 5.8 speed density (for now) it will drop right in and the harness will plug up fine & run on your current EEC. If you "wanted" a 5.8 EEC you should be able to source one in a junkyard easy enough as the speed density units are plentiful. The MAF 5.8 computers are the hard ones to find. Not sure if the SD 5.0s have a knock sensor on the back of the block or not but the 5.8 won't have one. Just leave that pigtail unplugged, it has NO affect on the engine control and won't even throw a code.

 

Also, cross check your current 5.0 firing order against the 5.8L firing order. Mine, being a '95 had the same firing order as the 5.8. Yours being a '91 truck 5.0 might have the older 302 or Non-HO firing order. If this is the case you'll definately want to pick up a 5.8 EEC to ensure everything is on the same page.

 

Engine firing order doesn't matter with SD, the exact same injectors batches are used on both motors so a 5.0 SD harness will plug into a 5.8 and work just fine.

 

The 5.0 ecu will run the 5.8, just not to its full potential since it is an sd truck and runs off preset tables, it'll think your still pushing air flow for a 302 rather than 351.