So I'm not the biggest fan of my 2 barrel or carbs in general. I started out in a 91 f250 with speed density and that did alright on gas but this bronco is thirsty and I want to modernize it a bit. I've seen very little on the web about anyone putting the mass air flow on the modified 351 so I need guidance.
I have a wiring harness from a 96 box truck that had a 351 roller motor in it that I had put in another truck so hopefully I can use that. I know I need a computer and correct me if I'm wrong but I'm pretty sure I need one from a vehicle with a manual trans and my c6 will run like normal.
I plan on getting a four barrel intake manifold to throw a throttle body on top of and drill ot/ weld bung holes for injectors.
The only thing that has me worried about making all of this work is the distributor. I know I need a new one from a 351w to match the harness but don't know if it will seat properly or have the right gear and such to put in the 351m.
Another thought in the back of my mind is whether or not I'll have to trash everything if I ever want to swap out the parts to turn it into the 400m
Insight, advice, and experience greatly appreciated

 

That would be a good project but it won't deliver much if any improvement in fuel consumption because the engine it's going on is in such a low state of tune. What does that mean? The basic engine runs at a very low efficiency, it is a smog era motor so compression is low, the cam is tiny and all that adds up to an engine that only makes about 1/2 as much power as it should and therefore burns about twice as much fuel as it should. The new 5.0 Coyote engine runs 10.5:1 compression and makes 385hp but it can deliver 15-18mpg in a 6000lb truck because it also makes a similar amount of torque. Yes the EFI system helps it do that but this motor wouldn't do much worse with a carb on it.
To really see any gains from an EFI conversion the motor should be rebuilt to raise performance and efficiency, but if you're going to do that you might as well start with a 351w which will natively work with the conversion parts you have.
Conversely if you simply rebuilt the 351m with higher compression and a better cam then even a carb would deliver better fuel milage. Don't forget the rest of the package though, the truck needs sufficient gearing to move it's weight and deal with whatever size tires you have on it and a transmission that will help keep the engine in it's sweet spot.. more ratios are better here.

 

Dern, it can't ever be easy. May as well put in that 400 crank and the flat top pistons and probably new heads for it for better compression then putgo to maf.

 

found this website where these guys converted to fuel injection but it lacks a lot of details. 400m/351m EFI | 460 EFI Guys they claim to get 14-16 mpg but they also put an overdrive trans on it so i doubt my c6 would allow for that mileage

 

Yeah more transmission ratios is always better, that is why you are seeing 8sp and 10sp transmissions in the new trucks and CVT transmissions in some cars, it keeps the engine in the sweet spot all the time.

But just to be encouraging and show what is possible, I had a MAF equipped 5.8EFI in my '90 F150 4x4 and it would deliver close to 18mpg cruising on the highway at 70mph, but it did have an AOD trans and nothing bigger than 31" tires. Around town it only averaged about 13mpg though and that is about as good as can be expected, the more a vehicle weighs and the bigger the engine the more gas it will burn, doesn't matter how much technology you throw at it that won't change.