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Most mpg's 302, 347, 351?

bigmuddy

Contributor
Bronco Guru
Joined
Dec 28, 2004
Messages
7,001
Loc.
Marthasville Missouri
I run an EFI 5.0 with the explorer upper and lower attached to the ZF manual overdrive. tires are 35 inches with 4.56 gears in the axles.

Around town and down the highway it is way more power than I need. But in the hills I tend to spend more time in 4th gear if I am in the 50-60 MPH zone. Otherwise I am shifting down to 4th and the motor does just fine. Overall I am happy with it but I suspect if I had the 5.8 I could probably spend more time in 5th gear when in the hills before having to shift down.

The reason I went 5.0 is that after having the 5.8 in another early bronco I didn't really care for the size constraints under the hood. (don't laugh bax or bill) The 5.0 is any easy install and fits perfectly and I was able to retain the stock radiator which works great (runs around 195 or less all day)

I suspect that one of these days I will probably swap the heads out for something that flows much better? The explorer GT90P heads are supposed to be good for another 50 hp and can be found relatively cheaply but headers are a bitch. Anyway, is I like my setup but it could use some more HP and torque in the hills or maybe I am just a lazy bastard that needs an auto tranny :cool:

Ben
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
As others have said its all in the gearing for the most part. One other thing is camshaft selection it should be matched to your gearing and driving needs. All said and done a 351W will get about the same mileage as the 302 and have more power to boot. but the 5.0's are a little easier on the EFI side.

Hey Bigmuddy dont plan on getting 50hp out of the P heads unless your going to turn it 6000+ RPM and do some port work 35hp or so is the max and most of it will still be high in the rpm range. There are really much better heads out there considering.
 

roundhouse

Bronco Guru
Joined
Sep 5, 2003
Messages
2,886
no yr not. You are illustrating a basic fundamental..it takes x HP to go y MPH and it matters not one wit whether yr running 6 Briggs an Strattons or a 514 stroked 460. What matters is one thing only..how well you matched up whatever you are running with its highest SFC operating point and the speed yr wanting to travel.


It matters. a 351 or 400M guzzles more gas and makes less HP than any other engine on the planet.

Swapping out a M engine for a 429 triples the power and normally gets better MPG. An M engine is rated at 125 HP, a 429 is conservatively rated at 375 HP. The bone stock 429 in my 69 Thunderbird would absolutely fry the tires for about a half mile or until about 30 seconds after it shifted into third gear, whichever came first.

That said, go with the 351.

They are in most every 3/4 ton truck and van and some Broncos.
at $4 a gallon, you cant give an 8 mpg van away.

And in some 89-91 ? Broncos, a friend of mine has a 88 with a 351W and a C-6

You will need to swap the upper intake and use BC broncos adapter.

Also the Ford trans is crap. We have a 94 and a 96 E-250 van. and both transmissions crapped out at less than 90K.



My 96 4-Runner has 250K on it and the trans is tight as the day it rolled out of the factory.

The GM 700R4 is a much stronger trans, since Ford brilliantly used a HOLLOW output shaft on their trans.

Apparently that decision was made by the same jugheads at Ford that sell a 65 MPG turbo diesel in Europe, but refuse to offer it here in the states.....
 
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