How much does a 1981 F-100 weigh? 300 six, 4 speed, 2 wd, style side short bed? Is the style side more aerodynamic than the flare side?

Is a style side bed lighter than a flare side? I am looking at one to build for fuel economy. I do a lot of highway driving. Thanks, Tim

 

What 4sp are you talking about?
A T18 is damn heavy and does not have over drive were the SROD is lighter and has OD.
Truck have AC or not?

Between the 2 beds I would think the smooth style side would be better.
As for bed weight style side has a metal floor and a thick heave tail gate.
Flare side has wood floor and a thine lighter tail gate.

If you do a search there is a post on a member running MPG numbers on his truck and what he did to get there.
Dave - - - -

 

I read an article a while back that claimed a 4x2 Bullnose Flareside pickup weighed in the area of 3450 lbs. That was with a 302, and I forget which trans. I have no idea if that was correct or not, it's just what I read. I've been meaning to weigh my truck, but haven't gotten around to it yet. I would assume that the Flareside bed is lighter than the Styleside bed by 100-150 lbs, if not more (Just guessing. There's not much to the Flareside bed. The fiberglass fenders weigh nothing, and the steel bed sides barely weigh more than the tail gate. Still...the 3/4" thick wood floor might weigh more than Styleside steel floor...no idea). I'd guess that the Styleside bed would be more aerodynamic.

So there. My opinion is that the Flareside would have a slight weight advantage, and the Styleside would have a slight aero advantage, which would likely make them even all things considered. In the world of Bullnose MPG, discussing either bed is probably splitting hairs anyway. I'd think that the Bullnose truck is blunt enough that the bed style probably doesn't matter all that much.

Interesting thread below if you're interested in 300/6 Bullnose fuel economy:

https://www.ford-trucks.com/forums/1...-9l-300-a.html

I'm casually looking for a 2nd Bullnose project truck, and I too was interested in a MPG build. I was thinking 4x2 short bed with 300/6, 5spd manual, 3.08 or taller rear diff, and little tires. (I already picked up a spare 5spd in case I should find a good candidate for the swap). However, I'm also interested in a 4x4 Flareside, so if I find one of those for a reasonable price, the "economy" project will be out the door.

 

My son has a 1981 F-150 4x4. It has a 300, NP435, 3.50 differentials. My 1979 F-150 4x4 has the same power train and gearing. He can get 19 MPG and the best I can get is 16 MPG. I don't remember how much more my truck weighs, but the difference between them was significant when we weighed them on the scales at the elevator. Weight is a big factor in fuel economy, so the lighter the truck the better. That is why I was looking at a 1981 F-100 short bed I found locally. It is a 4x2 style side with a 300 six, T-18 trans, 3.25 rear, and no A/C.

 

My 1986 F150 short wheel base, 4.9L, 4 speed manual OD with factory A/C weighs right at 3750#, according to the scales at the city dump.

Regarding the comparison between the 1979 and 1981 trucks, Ford advertised that 1980 was their first "aerodynamic" styled truck.

Please keep us informed of your progress.

 

I wonder how that would do MPG wise?
My 81 flare side has a 300 six, T-18 trans, 2.75 rear gear, no AC.
My parts truck 81 style side long bed had a 300 six (I did not get the motor), SROD trans (over drive), 2.47 rear gear, AC.
It is funny that the truck with the over drive trany also had the higher gear ratio.

I do not know what either of them weigh or got for MPG as I have yet to get the flare side on the road.
I have also added some things to the flare side truck like AC, duel fuel tanks (more weight) and replaced the wood floor with a style side metal floor.
I have also replaced the log style exh manifold with EFI ones that flow a little better and should help the MPG, still using the factory stock intake & carb.
I am told it should get mid to high teens MPG and would be happy with that.

In the long run I would like to go with a 3.50 rear gear and a add on over drive unit like Gear Vender or Advance Adaptors Range Splitter as the will be used as a back up to pull my car trailer when needed.
Dave ----

 

I previously owned a 1984 F150 short wheel base with 4.9L, 4 speed manual OD, 2.47 rear gears and factory chin spoiler. This truck has been in my family since 1999. Before the advent of gasohol, at 60-65 mph on the highway, it would return a solid 26 mpg!

With 3.55 rear gears and gasohol, the same truck now gets about 22-23 mpg.

 

The trucks that came with the SROD and tall diff gears must have also had the small 215/75-15 tires on them as well? I would think that they'd be a little too long legged with anything larger, but I'm just guessing.

Why not just install a 5spd Dave? Rather than the gear vendors OD, etc...

They're cheap and easy to swap in with mostly all factory parts and minimal fuss.

 

Just out of curiosity, what were the RPM's of this truck at 60-65 mph when the 2.47 diff was still installed?

 

Last time I left the dump my full float 83 F250 HD 351w 4x4 C6 longbed weighed 3640 empty.

 

Approximately 1350 RPMs.

 

Oh wow...that's very low. My '84 with 3.08 gears and 5spd swapped in now runs about 1750-1800 RPM at 60-65MPH, and I thought I was doing well to get it that low.
That 2.47 rear diff must make a big difference (I'm too lazy to do the math at the moment...lol).

 

The 2.47 pinion gear looks like a big pumpkin!

 

I just checked the door stickers for both trucks and both had the same size, small 215/75R-15 tires, both also had the same GVWR of 4700.

2 reasons not going 5sp.
The big one is needing to go hyd. clutch and building up the fire wall so it will not crack. Besides I rebuilt the clutch linkage and want to see how long it lasts.
I don't have one LOL really what I have seen posted once bought (ZF) it would need a rebuild so more money.
I like the T18 as it is a truck trany and with the granny gear good for getting heavy loads moving.

I hear the GV is some $$ and you cant use it below I think it was 30 MPH so using it in granny low is out and that is where I would most likely use it besides the OD.

Now the Range Splitter is cheaper and you can use it in any gear at any speed. It has it's own shifter handle so you would have 2 stick out of the floor.
I have heard of some using electric solenoid to move the lever on the side of the splitter and not run the handle thru the floor. You then use a push / pull switch like used on 2sp rear axles.
Just the way I am thinking at this time.
Dave ----

 

Yes, understood. I guess we're all different as I actually prefer the hydraulic clutch. The Terrapin reinforcement plate takes care of potential firewall issues. It really is a nice piece and well worth the money in my opinion. But, if you rebuilt the mechanical linkage and it's working fine, then yes, I'd leave it as it is. In my case, I already had a factory hydraulic clutch truck, and the 5spd was relatively inexpensive. I like the M5OD because it's a truck transmission, but I know others would NOT want it for that same reason (Some guys want something like a Mustang 5spd for a more sporty feel).

If my truck had had the SROD with OD already in it, then I might have been inclined to leave it alone and not even bother with the 5spd swap. However, that 3-on-the-tree had to go. If it had had a 4spd with a granny low first...I dunno, I probably would have ripped it out as well. I like those transmissions (my old 1980 Bullnose had the NP435), but my current goal was to get the thing a normal geared trans with OD.