250 MPG suggestions

[shelby987]

I am tinkering with the idea of squeezing some mileage out of a 70 3/4t 4x4.....right now with a 3 spd. manual and a stock 250, I can avg. 14mpg....I have to upgrade some things anyway, so I thought maybe the goal could be mpg, here is what I am thinking of doing, was hoping someone might have additional input, suggestions.

Currently do not have manual hubs, going to add those
Switch to an electric fan inplace of the flexilite
Have a recently rebuilt 250 to replace tired 250, the port and polish of a 230 head will mean 93 octane will be required.
I have a set of clifford headers, any suggestions on pipe size to max. mpg?
Offenhauser intake, looking to use a 2bbl tbi setup with a spacer in place of the 650cfm carb currently in place.
The head has oversized 396 valves according to the PO, the cam in there is unknown aside from ("its the high performance one"), should I look into a more mild cam?
HEI setup with an accel coil
Looking to use an overdrive setup, and possibly swap gears out of the axles to something a little more tame, like 3.73's or lower.....pretty sure someone said they think they could be 4.56's right now.
Any other advice? Yes, I know great mpg in these trucks is almost pointless....but I am keeping my 250, its original and I like its torque....and I would like to make most of these mods anyway, but I was just wondering if there was something else obvisous I might be missing.

[70 shorty]

Your mods you're planning sound real similar to what's been done to my 250, except I have a 390 holley 4 barrel. It gets 10 mpg, wide open, cruising, loaded or unloaded. Mine's a 2wd with 3.73 gears and a 3 spd stick.

[truckster]

If you're going for MPG, the 93 octane is a bad idea. First, there's no way you'll increase MPG enough to offset the cost of the higher octane. Second, higher-octane fuel is more resistant to burning, which translates into (ever so slightly) less energy per gallon. Higher octane is used because it resists detonation in higher-compression engines, but many people mistakenly believe it increases performance. The only case where this is true is in engines in which the computer retards timing to offset knocking.

[stllookn]

Get skinny tires and pump them up to about 90 psi if they will take it. Reduced rolling resistance is a great way to get a little more bang for the gasoline $.

[70rs/ss]

I think your "performance cam" and and 93 octane are going to take you in the oposite direction than where you want to be. Leave it stock and if you want tbi that will help, but remember these came with one barrels and for a reason. They will handle a four barrel with the apropriate upgrades, but that lowers MPG. If looking for MPG leave it bone stock (or slight upgrades to cam) and use hei intake and header you mentioned with the tbi and your milage should increase or at least stay the same on 87 octane. Lowering your ratio from 4:56 to 3:73 or even 3:08 with help as well.

[shelby987]

well, I am aware that the higher octane is not the best way to go, can anyone recommend the best way to lower the compression, with the 230 port and polished heads, I am told the compression is somewhere in the 12:1 range...I had thought about thicker head gaskets, but I doubt that this will get me down enough to where I can run lower octane fuels.

Also, with the HEI setup, and a computer controlled tbi, will I need a specific HEI setup, or can that retard the timing for me?

I realize this will not get 30mpg, and 20mpg is almost as in-feasible....I just wanted to go the 250 route, the engine I purchased came with a certain number of goodies....and I would like to make the best of what I have while I have it.

Thanks all.....cam recommendations? Keep it....leave it?

[70rs/ss]

Originally Posted by shelby987

well, I am aware that the higher octane is not the best way to go, can anyone recommend the best way to lower the compression, with the 230 port and polished heads, I am told the compression is somewhere in the 12:1 range...I had thought about thicker head gaskets, but I doubt that this will get me down enough to where I can run lower octane fuels.

Also, with the HEI setup, and a computer controlled tbi, will I need a specific HEI setup, or can that retard the timing for me?

I realize this will not get 30mpg, and 20mpg is almost as in-feasible....I just wanted to go the 250 route, the engine I purchased came with a certain number of goodies....and I would like to make the best of what I have while I have it.

Thanks all.....cam recommendations? Keep it....leave it?

Port and polish does not necessarily mean high compression. The only to increase the compression is to mill the head down thus putting the valves closer to the piston or to put pop-up pistons in it. To make the most informed decisions I'd verify all the things PO said. If it has been ported and polished then the intake and exhaust ports will be smoother and bigger in most cases thus improving the flow of air (good for power as will as MPG. If he shaved the head, then yes the compression will go up, then high octane is a good idea. As the TBI it depends on the unit as to the hei you will need. Good luck, BTW a thicker headgasket with drop compression.

[SSC's76]

I'd like to see a picture of these chambers along with the pistons being used? I dont see how you come up with 12:1.

Anyway 2.5' single exh if you go split dual smaller is better.
Mild cam stock or somthing slightly bigger (RV).

[shelby987]

The compression is higher because a head from a 230 motor was used, the PO was told by the machine shop that the smaller chambers will bump the compression up to 12:1.

The pistons are forged pistons for a 327, that is all the PO knew....for the most part, the motor was dropped off at a machine shop that specializes in performance motors, and the parts used were based off of (from my loose interpretation) likely a hot rod build up, and probably a little from how to hot rod you inline 6 by Leo S.
The only thing that was not included in the 'article' the PO refered to was the 396 valves, and I believe the cam.....does this article ring a bell with anyone?

Sorry, wish I could give more information, I tried to pull as much outta the guy as he could remember.....thats why I am trying to find the best way to drop compression (aware I can use a thicker head gasket....anyone know the best place to look....can I use two?? I remember this was done on old corvair motors to balance out compression once the heads were cc'd).

Thanks

[FUNMUDDER]

If your 250 is souped like that and gets 14mpg, let it be. New GM trucks with 6.0 Vortecs only get 13.

[frogsmakr]

What would you use for a computer for the tbi setup?

[70rs/ss]

Originally Posted by shelby987

The compression is higher because a head from a 230 motor was used, the PO was told by the machine shop that the smaller chambers will bump the compression up to 12:1.

The pistons are forged pistons for a 327, that is all the PO knew....for the most part, the motor was dropped off at a machine shop that specializes in performance motors, and the parts used were based off of (from my loose interpretation) likely a hot rod build up, and probably a little from how to hot rod you inline 6 by Leo S.
The only thing that was not included in the 'article' the PO refered to was the 396 valves, and I believe the cam.....does this article ring a bell with anyone?

Sorry, wish I could give more information, I tried to pull as much outta the guy as he could remember.....thats why I am trying to find the best way to drop compression (aware I can use a thicker head gasket....anyone know the best place to look....can I use two?? I remember this was done on old corvair motors to balance out compression once the heads were cc'd).

Thanks

SCI makes copper headgaskets for V-8's and I am guessing for 250's as well. Not sure of the chamber size on a 230 head, but I am sure with some seaching on the web you could find it and I'd try to find the machine shop and get thier take on this engine.

[TP from Cntl PA]

I always wanted to put an NV4500 behind the 250 in our farm pickup(69 C-10)............But never got around to it.

[special-K]

Porting can reduce compression some.What cfm is the single bbl?If you can find a 2-stage 2bbl with a smaller primary cfm,it could help mileage and give more power when desired.I think you`re getting pretty good economy now.

[pritch]

I always thought that the 250 and 230 heads were the same, but the 194 head would raise the compression, if used on a 250/230. ???

[SSC's76]

So the inside of the engine has never been seen before?


Special-K touched on somthing here with the carb. My friend had a 80 F-150 with a 300. We swaped his 1bbl for a $40 2bbl adaptor and a motorcraft 2bbl from a V6 rustang. Figured it would be jetted faily lean, close to what the 1bbl was doing. He jumped from 13 MPG to 24 MPG just by swaping to a larger carb that could meter fuel better. Oddly enough power did not increase according to the butt dyno.

[shelby987]

wow....maybe swapping to the 2bbl for the time being is the way to go....I have a 4bbl intake, maybe for the time being until I can work out the legistics of the tbi, I can swap in a 5bbl to 2bbl adaptor plate and a carb......any ideas on where would be a good place to start looking for said carb?

As for the computer, I was thinking I would have to go for a custom jobber, like the megasquirt computer, I like the internal MAP, and the ability to customize to the engine parameters....not just a specific engine (i.e. 5.0, 5.7, 4.3, etc).

[SSC's76]

Theres a guy on ebay that sells them, he wants way too much for his rebuilds + adaptor I think he gets $400 per setup. You can still buy these carbs cheap in the bone yard $40 at most a kit is $15 and they are soo simple to rebuild I'd almost trust my 11 year old nephew with one, almost....

Heres a pic of what they look like, this ones on a Jeep.

[shelby987]

any leads toward what vehicles I should be looking for that would run these carbs? Who makes them?
Thanks

[70rs/ss]

Originally Posted by shelby987

any leads toward what vehicles I should be looking for that would run these carbs? Who makes them?
Thanks

You might find one done at autozone or checker auto, then you just need a core.

[SSC's76]

Originally Posted by shelby987

any leads toward what vehicles I should be looking for that would run these carbs? Who makes them?
Thanks

They are Ford Motorcraft 2bbl carbs. They are actually found on 1960's-early 1980's. They are on practicaly every ford application sine 98% of fords were 2bbl. I'd suggest you look for 70-80 model carbs from V6 cars. The one I mentioned above came from a 1980 Mustang V6, just by chance it was jetted perfect for the truck we used it on. If you find a V8 with one of these thats ok too since jets can be found very easy online.

[FUNMUDDER]

Originally Posted by SSC's76

He jumped from 13 MPG to 24 MPG just by swaping to a larger carb that could meter fuel better. Oddly enough power did not increase according to the butt dyno.

BUTT DYNO!!!!!!!!!!!!!! Thats a classic. I gotta remember that one. 305 does good according to my BUTT DYNO!!!!!!

[garthdader]

Speaking of MPG, has anyone tried adding acetone?? I heard that it increases MPG quite a bit..but I dont dare try myself. Anyone tried it?