I have a 1994 F-150 with a straight six sitting in it right now auto transmission. i'm going to be getting a 351w efi, i'm wanting to drop it in stock for now and do a few things later on to make it faster. I heard its pretty hard to get all the wiring to go right on efi, so i was wondering if it would be easier to go carb. I know efi has more hp and mpg, but i'm not looking to build a insanely fast motor, i also have a C4 transmission built to hold 800HP that i could use for the carb swap. I'm not really worried about mpg, i just want to know what would be easier to do.

 

The easiest in my opinion would be to swap wire harness and computer from donor truck with 351. Just my two cents worth.

 

theres a possibility the correct wiring harness doesnt come with it

 

True very true, although I would call around to the junkyards in yer area. Worth a shot at least.

 

X2 on looking in a junkyard for a harness. You say insanely fast, so I feel you are already trying to justify a carb swap. Well check out a Lightning forum and see how fast some of those guys are going with efi. As for the C4 I don't know how long one would last in a heavy truck that has a built 351, I thought those were fairly light duty for smaller cars.

 

Whoever told you the efi wiring is difficult, is crazy.
All you need is the engine harness. Snap it in the injectors, a handful of sensors, and the other end bolts to a square connector on the passenger fender.
Pull the 4.9 computer, stick the 5.8 computer in its place.
Done.

A truck 5.0 or 5.8 engine harness will work.

 

True but that only works with this truck if it is SD and not MAF and the engine harness is from the exact same year, otherwise all bets are off.

 

Now your making it sound way more complicated than it really is.

If it's SD, get SD, if it's mass air get mass air. That's a given.

If SD, make sure the computer not only matches displacement but your transmission.

Basic wiring is the same regardless of engine, across many years, some connectors are different but that's easily resolved, as the computer pinouts, are the same.

It's easy, only complicated if over thought.

 

Not really. If the truck is SD then a same year V8 engine harness will be plug and play, no problem there as all the sensors and actuators are the same just positioned differently and even though there are 2 more injectors there are still only 2 injector batches so no extra wiring needed.

But if it's MAF then those 2 extra injectors are a problem because wiring for them won't exist in the engine bay harness between the block connector and the PCM, so even if you did plug in an SEFI V8 engine harness you will have 2 dead injectors.

And early trucks didn't have a block connector on the engine harness they have several small round connectors which obviously won't just plug in, so the little details do matter.

 

How do I distinguish SD to MAF?

 

How did you make out on this project? Did you follow through? Did you pass on the swap?

1994 302, add a signature like we have, add some detail to your goals and tell us about the truck you're starting with.

Easy to tell a maf truck, as the airbox will have a single hose outlet. Sd trucks have two hoses out of the airbox.

All you need to do is match engine harness with the trans and efi you have currently. So if your truck is sd, and e4od, you find a 351 computer with an e4od, and wire harness, and it all bolts in. If you have mass air with e4od, you find a 302 mass air computer with e4od, and wire harness, and it bolts in. You won't find a 351 with mass air or a 4r70 trans, but a 302 computer will work just fine with a 351 if you have either of those items. It's not that hard of a swap if you get what you need first. I literally bolted one together in a weekend, by myself.
You'll need fuel lines from frame to fuel rail also. The 300 ones will work, but there's a little difference in them.