92 E150 with 351W and AOD-E, next April have travel itinerary planned and concerned about the poor fuel mileage i am getting. Aside from decreasing rolling friction by making sure the brakes aren't dragging and the tires are correctly inflated i have some mods in store for the engine and want your opinions on possible gains if any, first i will be using low restriction catalytic converters and muffler to minimize any back-pressure in the exhaust, then adding under-drive pulleys to slow down the accessories to reduce parasitic drains on the engine, add MSD Coil to increase combustion and possibly install re-curve distributor.
What can i expect to gain in terms of mileage, i know there will be performance gains but that is not what i am after..

 

well, i don't know your travel plans, but i will say that it would be wise to count the cost of your mods and compare that to the fuel savings you can expect, and decide from there whats likely to be worth doing.

catalyst - stock ones aren't restrictive at all unless they've failed and clogged up. unless yours is clogged up, you won't gain much of anything by replacing it.
muffler - a freer flowing one may help a little, as well as changing your exhaust pipes to one size bigger than stock.

ignition - you can't recurve the distributor except by reprograming the computer, because timing advance is entirely computer controlled.
the hotter coil may help a little

pulley changes - i've never heard of anyone doing this mod, but i see what you're thinking there. you'll want your water pump to spin at the same speed it always has, slowing down the alternator should be ok, power steering is most needed at low speeds, which often means low RPMs, so slowing it down may be problematic. AC if equipped should be fine slowed down but may be less effective.

for everything on your list, i would guess an improvement of about 5%

i would also consider a few other things...
o2 sensors - if they haven't been replaced in the last 100k miles, replace them
MAF sensor - clean it with the cleaner made for it.
basic tune up parts (plugs, wires, cap, rotor) - make sure they're in great shape, preferably new.
rearend - consider the speeds you normally drive at, and consider the option of changing the gear ratio if it would put you better into a better RPM range to suit your use, if it isn't already ideal.
tires - wide or aggressive tires eat more fuel than narrow highway tires.
overall weight - the less you weigh, the less fuel you burn.
driving style - your driving habits can make a huge difference in your fuel economy. let it lose a little speed climbing that hill, and let it gain a little going down the other side.
wind drag - vans are like a barn going down the highway - the wind does a lot to slow you down. any improvements you can make here would help a lot. they say one of the biggest improvements here is in reducing how much air flies under the vehicle, often achieved by an extra piece under the bumper, and by adding smooth panels under the vehicle in places that might cause funny wind currents.

just for the fun of it, what kind of MPG are you getting now, and how long of a trip are you planning for next spring?

 

Their are 2 catalytic converters installed, the first one has 2 inlets and feeds into a second cat with a single inlet, 1 or both of them are clogged and that is most of my problem. What i intend to do is cut off both of them and install a y-pipe and plumb it back into the muffler, before July 2015 i will have to re-install the cat's unless i move somewhere that doesn't require emissions testing for vehicle registration.
2.25" exhaust will have to stay for the moment.
My plan was to replace the entire distributor with a unit from SummitRacing.com like one from Proform or Professional Products, they both offer and adjustable timing curve.
The hotter will help a lot as the factory coil is known for being a little lame plus it is over 22 years old.
The Under-drive pulleys are good for 15hp and dirt cheap at $35/set.
The O2 sensor is on the list as well, over 117,000 miles on it and it surely can't be doing a very good job of reading oxygen content.
No MAF sensor with S/D, just a MAP and it's working fine.
The previous owner kept it tuned up with new parts.
Rear-gears are fine.
Tires are fine.
Gross weight is a concern and must be minmized.
My driving style is that of a 97 year woman, i am in no hurry.
The front spoiler is a great idea that works very well and i had forgotten until now, thank-you.
Can't put a number on the MPG but i can tell you it sux, i may be FOS but my goal is 20mpg on the hiway..
Cross-country from Portland Oregon to Richmond Virginia to Central Florida to Southern Mississippi to San Antonio and back to Portland..

 

What do you mean by poor fuel mileage? The best you can hope for is ~16mpg in a 1/2 ton van with a 351w.

 

About a year ago, I drove our van solo from Salt Lake City to San Jose setting cruise control within 5 mph of the limit as much as possible with AC running and stopping only for fuel. By my calculations, I didn't see better than 16 mpg. I expect the advantage of driving on level ground offsets carrying a load. Our '97 Suburban turbodiesel can get 20 mpg fully loaded on better Oregon fuel and lower Oregon speed limits. Never on the cr@p California pumps dispense.

The list of improvements suggests you might not put enough miles over your ownership of the van to recover your time, labor and cash investment in improved fuel economy. If $500 gets you from 16 mpg to 20 mpg, it would take 15K miles to recover the investment at a fuel cost of $3.50/gal. It would take 30K miles if it only gets you to 18 mpg. Hopefully that's only a few months' driving for you.

I know some 97 year olds who are always in a hurry

Sixto
93 E150 Chateau 5.8 185K miles

 

you said your catalyst is plugged up - so to eliminate or replace it will help a lot. i used to have an old LTD, and when the cat plugged up, it just about doubled by fuel consumption.

outside of that, you're looking at fairly small gains.

 

The A/C compressor is locked-up and not getting replaced so I don't have that to further reduce mileage. The Cat's are totally clogged and the van surges and bucks when any kind of load is applied because the exhaust can't escape fast enough, all you hear out the tail-pipe is a choked sounding whoosh of air and no sign of an engine note or rumble, the EPA might see that as a good thing but it does no good for performance or mileage..
I will remove the Cat's and see what happens, i will probably be ecstatic over the improvements and leave everything else alone..

 

Leave the factory distributor in there. Trying to replace it with anything else will create far more problems than you'll ever hope to fix. There's nothing wrong with the factory TFI distributor, as Josh said, all you need is a good tuneup, new cap and rotor (get the brass terminal units, the aluminum units suck) get a good set of plug wires (I like the Ford Racing 9MM wires, they'll last 3-4 years in the hot box ) also change the plugs, good ole Autolite copper plus will do, just make sure to check the gaps before installing them. The underdrive pulley set ? Ditch that idea too, you will not see the gains that you listed, you will create yet more problems (overheating, under charging the battery, underdriving the A/C and putting it in a bind) As for rear gears, if it's got 308's, it'll get better mileage with 3.55's, the accelleration will be helped too. You will never see 20 mpg though, no matter what you do. You might get that on occasion running downhill with a tailwind, but as a rule, 14-16 is doing good in a van. My 95 E150's best in 10 years I had it was 16 mpg running on I-10 along the Gulf Coast. A bottle of Lucas transmission treatment was responsible for that, before adding the Lucas, 13-14 was the norm.

 

I have achieved 20 mpg on one trip with the minty 91 E-150 w/ 4.9 inline six I just bought. I can't see how you could top that with any V8.

My Pathfinder E-250 w/ 351 gets at best 12. My Pathfinder E-350 w/ 460 has never gotten better than 10.

 

10mpg would be an improvement..

 

You're not even getting "10mpg"?

Google 'Engine Grenade'.

Seriously, you should expect no better than 14 mpg under the best circumstances.

 

Just to give the OP an idea of mileage potential, we just bought a 96 E150 conversion van, roller 351W with mass air EFI, no idea as to when it was last tuned up (if ever, it's got the original spark plug wires on it) The cats are missing (removed by the previous owner I assume) 3.55 rear E4OD transmission. The dealer we bought it from tossed in a free tank of gas due to the exhaust leak they discovered in the pass side manifold, so I'm sure they filled with the cheapest gas available. First fillup coming home it got 14.25 mpg running 65-70 mph all the way back with some city driving in the mix. Coming soon: a set of GT40 iron heads, 1.7 Cobra roller rockers and shorty headers to increase the HP & torque

 

Thanks baddad457, that is the info i was waiting for and gives me great idea of what to expect with mine, even though my 5.8 is not a roller or MAF sensor equipped the mileage figures should be fairly close, keep me posted with your updates..!

 

I am late to this thread but any "hot rodding" techniques like opening up the exhaust or intake (unless they are plugged) and underdrive pulleys will be minimal and will never pay for themselves with gas savings. Your main enemies in a steady state cruise are wind resistance (huge frontal area), rolling resistance (tires and vehicle weight), and mechanical friction (which you can do very little about).

You say "tires are fine" but I say think harder about the tires. What size and brand/type are they? Michelin LTX M/S tires may give you as much as 1-2 mpg over no-name tires and especially all terrain type tires.

I have been driving big vans since 1986, and freeway mileage at reasonable speeds (say 65-75) have been:

'73 Ford Flatnose E200 Turtle Top conversion, 302 with C6: 12-13 mpg

'86 GMC 2500 Turtle Top w/carbureted 305, Turbo 350 trans with lockup torque converter: 13 mpg (changed 2.73 axle to 3.42 and gained performance and with no effect on mileage)

'96 GMC Savana, 350, 4L60E trans, 3.42 axle: 15-16 mpg, lost 1 mpg going to 255/70 tires. Tires looked cool but used gas. Overdrive transmissions and fuel injection work.

'02 Ford E150 mild low roof conversion, 4R70W, 3.55 axle, Michelin LTX M/S tires: 17-18 mpg with light loads. This is as good as any big van will get. (Tried 30x9.50 Firestone Destination AT tires and lost 2 mpg adjusting for diameter increase--returned them under Firestone 30 day warranty and got another set of Michelins) I am certain I could crack 20 mpg in my van if I kept my speed down to 60 but I refuse to do that.

Basically, the 4.6 is the mileage king of all full size American vans and I believe with light loads will beat any other full size gasoline van. Heavy loads will kill the mileage. (I did have a '78 F100 pickup with 300 inch six and 4 speed manual OD trans that would get 20-22 mpg, but that was a 3600 lb truck with a 2.75 axle and a final drive ratio of 2.18...and that was the day of the national 55 mph speed limit)

Good luck, but I am thinking that many of your proposed mods are shadetree engineering things like the old JC Whitney catalogs that will gain you very little mpg. Again, low rolling resistance tires, unplugged exhaust IF IT IS PLUGGED, and driving like a little old lady will be the main factors. You could also build an air dam to go under the front bumper and that would help a tiny bit. Any other body smoothing (taping seams, folding mirrors) might help a tiny bit. (There was a guy on FTE that got 30 mpg out of an Explorer, but he did a lot of crazy stuff and probably spent more on mods than he saved on gas.) Synthetic rear axle fluid and engine oil might be a good placebo and won't hurt.

Big trucks use lots of gas. I don't think you'll see 20 mpg out of a 351. Hotrod mods ain't gonna get you anywhere, really. If you are cruising under 2000 rpm, things like exhaust back pressure really are not an issue unless you are really plugged up. If you run the numbers, you might find that renting a modern minivan for the trip will be more economical...

Good luck,
George

 

The problem is i can't find rental minivans with wheelchair lift and hand controls as standard equipment so i am kinda stuck with trying to get the best i can from what i got
The biggest and only problem i have is a severely restricted exhaust, the muffler is fine but the cat's are clogged, i finally bought a reciprocating saw so it won't be long before the cat's get replaced with a pair of modern units. On my van there is 2 cat's, the first cat is a 2 into 1 unit and then there is another single inlet cast after that, i don't know whether one or both are clogged but i will start with the secondary cat and work my way forward until i find the restriction..