Aerodynamics & weight.

You're comparing apples to oranges here. What works in a car will not necessarily work on a full size van.

Dude, the Park is like a Corvette compared to an E150 being a freakin' barn. It's not just rpm's, it's the vehicle. I have owned a full size van of one kind or another since 1986, and a Ford pickup before them, back to 1978. I have also owned everything from 426 hemi muscle cars to Corvettes to front and rear wheel drive 4 cylinder economy cars to Olds 98's. A 302 in a big van needs to rev. It has a 3" stroke, shorter than the stroke in my 4.6 (which is a 281). If you want low rpm torque, build a 300 inch six or a diesel.

2.73 ain't gonna work. If you know better, do it and report back. We'll put a photo of your van by the definition of "badly lugging engine" in the dictionary.

George

I'm talking about doing a gear swap in a rear axle costing $1000, that's why many find a replacement with the gear set of their choice and swap the entire thing.
A van is NOT a car, they lack the aerodynamics, apparently you haven't listened to what others are saying so go right ahead, you'll be wasting your money. BTW I had a dodge van with 2.54 gears, it was gutless, barely pull out of our steep driveway, and it was without overdrive, if it had, it'd have not been able to stay in it.

OK, I was just making a point that the lower the RPM usually means better gas mileage. I also agree that the rpm's can go too low. According to Randy's Ratio Calculator my current rpm's at 70 mph with a 3:07 ratio is 1825. With a 2:73 ratio 1623 rpm's about about a 200 rpm drop. According to this web page a small block Ford should be able to handle 1800 rpm's. Maybe a little low still thinking about it. I need to look at some more cam data. Crane is selling what they call a towing cam for trucks. Anybody ever try one?

It seems your determined to find a way to spend money on your Van. Please report all findings...

Yep, installed an RV cam in my 4x4 truck, and as stated above, it raises the HP and TQ curve to a higher RPM, the opposite of what you're wanting, sorry there is no lower than stock cams either.
When you manage to do this, up date us on how long it takes before you smoke the transmission from sporadic shifting while trying to locate the proper gear.

How did you make the custom air box? i want to do the same thing for my econoline. what air filter did you build it around? and ow did you modify the cold air intake?

i have built custom air intakes for motorcycles, I would like to put a couple of filters directlly onto the econolines carb intakes-, and maybe an air filter bag over them, but would the air not be cold enough if the air filter is under the hood with no cold air intake duct work?

I run 2250 at 72 mph with a 3.73 the top gear in the aode is .68 od that a pretty step od but i do get 15 mpg. if i were to rebuild i would stroke to a 331 cid and run the mustang camshaft it is a really good tourqe cam. and use a set of the explorer gt 40 heads.

I took the snorkel tube off and drilled a new hole in the side of the box below the filter for the PVC valve hose and re-stalled it. I drilled more 1" holes in the front of the box below the filter to relive the restriction at the opening of the box and added a K&N filter. When I did this I also put on a 1" throttle body spacer. Somebody made the comment that I was just looking for a way to spend money on my van. Yes, they are correct. I try and make some upgrade every year before my 2300 mile spring break road trip. This year will be no exception.

I was probably overestimating the O/D gear ratio in my post above when I guessed 1600 rpm at 60 mph. Instead, you're at 1600 rpm at 70 mph. EPIC FAIL in a big van...might be able to handle a motorcycle application or a Cobra kit car. Even 1800 rpm's is not enough for a big van at 70 mph with a low torque motor like a 302.

No idea what you mean about "should be able to handle 1800 rpm's". How close is your torque and horsepower peak to 1600 rpm? Your engine probably puts out about 60 horsepower at that rpm...

George

According to the ratio calculator my stock factory set up is 1825 rpm's at 70 mph. That is 235/75/r15 tires at 27.7" tall 3.07 rear end and a .7 final drive ratio. I have had my van for 10 years when you predict my transmission failure will happen? Also is the cam in the link below what will not work in my van. I have asked Jegs for horse power and torque curves comparing it to the Ford cam. I will report the answer.

John

Comp Cams 31-255-5 Comp Cams Computer Controlled Series Cams

We are just about there on rpm except a 235/75x15" tire is nominally 28.8-29" tall, which will cut your calculated rpm to about 1750 at 70 mph with your existing gearing.

The final drive is virtually identical to my old '78 F100 pickup (2.75 axle with a .79 or .8 overdrive), which was 1200-1500 lbs lighter than your van, had a smaller frontal area, and which I used only for light loads. It was a short bed stepside that I bought new for a 60 mile daily roundtrip commute. And that truck had a 300 inch six which had its torque peak AT 1600 RPM's. Repeat--torque peak at 1600 rpm.

The 300 was a 4x4 bore/stroke motor which worked well at low rpm. I remember renting a 12 foot box moving truck with the 300 and it was slow but did the job. It was also used in UPS trucks. The 300 was designed as a low rpm TRUCK motor.

The 302 is a 4x3 bore/stroke motor which does not work well at low rpm--I've had 2 or 3 vehicles with 302's and remember them pretty well. They were derived from the 221 Falcon V8 and were designed for small cars. Not big vans.

Your van is geared way too long as it is, and if you change the axle to a 2.73 it will be even more of an Epic Fail. Gas mileage is not determined solely by engine RPM. Please understand I enjoy science experiments too, but yours seems about as likely to succeed as me building a pair of wings for my arms and flying a mile. If you want to improve gas mileage, build yourself a streamlined nose cone, chop the top, put on a low front spoiler, and take 1500 lbs of weight out of your van. Then run it on 4 motorcycle tires, or maybe move to metal wheels and run it on a train track. :)

George

I want the smiley banging his head against the wall to add here.
I've always called the 302 a car engine, feel the same way about the 4.6, it's not just the weight, its the mass against the wind, you get a clue of how much when driving on a windy day.
He asked a question, we've all answered, now there is 2 pages of arguing the fact, so- since you know everything and plan on doing what you want, WTF did you ask for?

Haha, so true!


To the OP, put some 3.55s in and just live with the mileage.

You will have a happy motor and trany that way, pull hills and gain speed better and should not lose any MPGs because it will not be lugging all the time.

You might even gain a little!