you will never, ever convince me carb can be better than FI for efficiency. The one thing carb has on EFI is mechanical simplicity..
when you're dealing with formulas? sometimes it's easier to just pull put a bigger hammer to get the job done and not really think about it.

It's easier to keep a carb at 100% efficiency.. heck, I'm a computer technician, programmer and wannabe (and eventual) software and hardware engineer and can't keep my stupid EFI running right. So EFI at 60% versus carb at 90% that every joe-blow can handle eventually?

err uh, too much of the sweet water. Point is, carb is easier to keep running right, EFI wants to lie and dump fuel or waste power because one signal is a tad wrong. In a perfect environment, I'd always, 100% of the time bet on EFI for efficiency.. but yeah

 

According to a website I just read states that the 400 made 172hp @4000 rpm? So it sounds like 5000 rpm would be the ceiling for revving a stock 400.

So the airflow requirement for the carb on a stock 400 with a peak rpm of 5000 rpm would be something like 434cfm. A 490 4bbl Holley on a 4bbl intake would be perfect for it. A down-jetted 600 Holley would work well, too, but you'd probably lose a small amount of efficiency.

This online cfm calculator I just found makes things quick and easy:
Carb CFM Calculator

 

Oh ok thanks american thunder. I plan on doing a 4bbl conversion eventually cause right now i have the stock 2bbl. It is definitely out of tune though if it floods when i floor it while driving. I didn't tune it nor do i really know the little tricks to get it perfect but once it is warm it runs pretty smooth.

My 88 ranger was EFI and i loved not having to worry about it dieing or faulting somehow, but i hated how the system would completely die and just go down the chute with a few small problems.

 

The '83 4x4 Bronco I put together using a 1970s 300 inline 6 that I'd rebuilt along with a 5-speed trans I'd swapped in, a points distributor and a stock 1bbl carburetor got 23 mpg going to work and back everyday for 2 years. The motor was 100% stock, other than my retuning the carb and running more ignition advance with a modified advance curve.

I'm not sure what a stock '90s injected Bronco with the same 300 motor as mine averaged for fuel mileage, but I bet mine was at least as good, if not better. The newer 300 has the advantage of higher compression also, which increases efficiency. I don't know if carbs will be more efficient than injection, I said they'd rival it in the best situations. And one of the big magazines (muscle mustangs and fast fords? ) ran a dyno shootout years ago. A small block v8 was tested first with injection, then switched over to a barry grant Race Demon carb, and the carb setup made more hp than the injection. My Mustang gets 13 mpg on the highway with a carb,(although extremely bad 1-2 mpg around town, likely because I'm usually smoking the tires) and I highly doubt the mpg would be any better with injection, and I'm positive it would lose power if I switched it over to injection. You should hear the throttle response with that carb..

 

p.s. What I always say is, if you want fuel injection, go diesel! (mechanical injection kicks ***)

 

Haha. hey i have a question since you seem to know your stuff, is my 400M a small block or big block? I was thinking big block but i have read otherwise.

 

Just regarding displacement it can be considered a big block (that's chevy talk, btw), but since it's derived from the Cleveland family (some Ford talk now) and the 351M it can be considered a small block (aaaand back to the starting point).

 

Gotcha... I'll say medium block then :P

 

Technically the 460 is a Cleveland by design. I like medium block though

 

I've always said that the "M" stands for "Mutant", because that's what it is.. Big block bellhousing but small block heads.

351/400 MUTANT.

 

I like the Mutant name for a 400 Mutant medium block.

 

I was thinking about converting my 300 EFI to carb. I'm getting 17 MPG if I am calculating right but I also have my check engine light on as well. Would be sweet getting 23 mpg with it. Kinda wish I could have gotten a 78-79 Bronco with a 300 I6 in it and put a 5 spd in it.

 

I wasn't aware they offered the 300 in either year Bronco but I will say, my '79 only gets 9mpg.

 

I won't know what my 78 gets till i filler up in a few weeks. I just spent $72 to fill it up from half a tank so we shall see.

 

They didn't. Only the 351M and 400 were offered. A 300 would be a custom job. I've seen a few who've done it and they're pretty cool.