I am considering picking up a rebuildable 4.0 to try to maximize fuel efficiency first and performance if possible. These are some of the things I was looking at:

• a "mileage" cam kit if available
• doing some port matching on the intake and exhaust manifolds. I don't think polishing helps fuel efficiency
• a multi-angle valve job - performance valves perhaps?

What else should I consider? Nothing too radical (expensive).

 

You will absolutely love the mileage cam. I did this once on a 454 and the results were absurdly positive. Low range torque went through the roof and became wonderful to drive.

It became like a diesel, gobs of instant torque. I'm sure there was a loss of max power someplace but it was NEVER apparent in driving this heavily loaded and working 30,000 lb vehicle.

Never put an RV cam in, I did this too and it stunk.

Ken

 

for max. fuel economy, if you have 2wdr Aero?, change rear end ratio to 3.08 or 2.56
won't be great off the line or a towing machine but great highway cruiser at 75 mph
want to get cruise rpm 1800>2k rpm in OD
run tires at max sidewall listed pressure
install a vacuum gauge and drive by it
will lose in town city mileage

if '96 or newer, calibrate PSOM to new rear end ratio, helps guide the PCM to better fuel mileage
after rear end in, disconnect neg. batt. lead to force PCM relearn of engine parameters
4L already has mileage cam
polishing exhaust ports will help mileage a small amount....

best city mileage rig is one of the new light weight 4 cyl import hybrids

 

The cam could be a good idea

DO NOT POLISH anything on the intake side. It hurts fuel economy by up to 12%. Leave the intake surfaces alone. Without turbulence, you get poor atomization of the fuel. Without atomization, you get a poor quality burn.
The valves are alreay too large, leave them alone, or if the size was reduced by say 10%, you would get more low end, better economy, and it shouldn't hurt the high a noticeable amount.


For economies sake, the maximum rated tire pressure is fine, but you should not exceed the rateing on the sticker inside the door. Why, because all the suspension and drivetrain components are designed to run at the recommended rateing. Higher than that results in the same wear patterns as overinflation, handling becomes poor, etc.

 

Honestly there's not much you can do for mileage besides making everything correct. I wouldn't waste time messing withe engine other than a good balance job..As far as a cam I wouldn't think so I would think fords got that dialed in pretty good.



Dick

 

Vango,
what are u getting now for hwy and city mileage?
anything above 20 hwy is good, above 16 city is good

 

I have 3.0 and tried to do it.... MPG was lower, acceleration was bad, but max speed improved....
May be for 4.0 it has any sens...

 

I can't really complain for what the Aero is. I have a '93 2wd extended and I get around 17 in town and 22-24 on the highway if I'm not fighting a headwind.
I just thought that if I have to do a rebuild someday, I may as well put in a little more effort and try to optimize the engine performance. If I buy a rebuildable junker I can take my time getting it right.
I'm really amazed that I have never had to do anything to the engine besides consumables like belts, fluids etc. I still have the original waterpump and engine accessories.
My only complaint is an oil leak on the back of the intake manifold that looks like a faulty factory gasket installation.

 

> a multi-angle valve job - performance valves perhaps?

All this refers to is matching the grind on the valve exactly to the grind on the head. It really only applies to "old" tech where the valve was a simple degree sealing surface when they were using leaded gas. I think you will find most modern engines have a bit more thought delivered to the valve seating and sealing surfaces today and just rebuilding the head makes it "multi-angle" by default.

The best thing for a 4.0 is to leave it stock, use Motorcraft plugs, and maybe open up the exhaust.

 

My '96 4.0 w 163K miles extended got 20 mpg on the last tank ful with AC on, 500 lb cargo, half flat interstate and half windy 2 lane mountain roads. Only mods are KN air filter, 225-70-14 Michelin light truck tires at 32 psi. I think the stiff tires do help, not as cushy, though. Driving 64-65 on cruise control helps a lot.

 

A performance reusable air filter should definately be kept on the list. Small price to pay and you won't have to pitch any old paper ones out.

 

Oh come on, a performance reusable performance air filter is about the worst thing you can buy for these. The #1 most importnat sensor for governing the air/fuel artio is the MAf sensor, which gets messed up when you use an oil based filter. I used to have the K&N, at first it seems to have better power, and the economy was pretty good. Less that 3,000 miles latter, it was plugged, while the paper filters were good for well over a year. Also, the first time I went to clean it, there was an oily film on the screen of the MAF sensor. I cleaner the filter and reinstalled it, had no improvement to economy or power. Removed again and cleaned the MAF sensor, economy restored, but how many times do you think you can do this? Replaced with Purolator paper filter, economy was even better than with K&N, and I don't have to worry about the MAF getting messed up. For economy, longevity, and convenience, the good high quality paper filter beats the K&N hands down. The only area the K&N is better is off road, or race environements, where the vehicle gets totally rebuilt after each race anyway. And if a K&N gets wet, it won't collapse. Oh, before I forget, the film on the MAF screen wasn't just oily, it was mixed with really fine dust. Makes you wonder how much stuff the K&N removes.

 

Different experience than I've had with my K&N as well as many others I know with them. They are proven for regular driving conditions as well. This is the was the case do to your MAF sensor, the filters aren't meant to be overoiled, did you ever add to the oiling?

 

"performance reusable performance air filter is about the worst thing you can buy for these. "

My experience has not parallelled yours. My 96 4.0 has 162K, well over 100K on the same K&N air filter, which I've cleaned 3or4 times in that period. The engine uses no oil between changes. I did have to replace the o2 sensors once, but nothing else related to airflow or fuel.

 

From all the threads I've been around keep the stock filter and save your money..




Dick