Forgive me as I expect this has been asked and answered many times.

I have a stock 1985 E150 van with a 302/aod 2 barrel carb. It has the California emissions package. I have replaced the converter and know the exhaust is not plugged.

The engine lacks power and only gets about 10 MPG. If I am running 65 to 70 at sea level and the freeway climbs over an overpass I have to mash on the throttle and drop out of overdrive to hold my speed.

I know the van is heavy, and cuts lots of wind, but this seems ridiculous. It is a real dog. I have driven some newer V6 vans that would run rings around it.

What about this series of engines that make them perform so poorly? Am I turning it too slow? What is the best compromise RPM between power, longevity, and economy? What RPM is best to cruse at?

I know it will never be a speed demon, but I would like to keep up with traffic and get reasonable fuel mileage. Is that to much to expect from a rig like this?

 

Ford needs to be slapped for a few things they did on the '80's trucks. The first is the cams they put in the windsor engines... pathetic is an understatement. They were looking for low emissions so they didn't let the valve open very much... something in the neighborhood of 0.360 total lift, and way under 200 degrees duration. Needless to say the motors are smothered. The second thing they did was put high gearing(low numerically) in the axles, something you would see in a vehicle with a 3-speed transmission. If you are really unlucky you got both of these.. the cam you definitely have, the gears you need to check. There should be a small tag hanging off a rear diff cover bolt. The first 4 characters are the gear ratio and open or limited slip diff. So 3L55 is a 3.55 gears with a limited slip. 3 08 is 3.08 gears with an open diff.
If you have 3.55 or 3.73 gearing and stock size tires then you are pretty good there, if you have 3.08 or less you need a change. After that, your best bet is a cam upgrade. Crane and Comp cams, as well as others, have a selection that are emissions legal and will really wake the motor up. Be aware the 5.0 is no torque monster so even with a cam it will still need to shift on the big hills.. but it should have no problems towing it's own *** around on flatter freeways.

 

emissions 302s in stock form are turds...to say it nicely. You're limited to what you can do because of california emission rules, but you're gonna have to deal unless you get a cam....or an older emissions exempt title and vin plate Then let the fun begin!!!!!

 

btw having the AOD tranny i doubt you have gear ratio issues. The really high "road" gears came with non-overdrive trannys, in my experience.

 

I've seen AOD's with 2.73 gears. Quite common in cars, and Town Cars don't weigh that much less than a van.

The entire upstairs of the engine is the problem. The heads are about the worst flow-wise, with the 255 heads taking the Worst-Ever Crown. Upgrade to some E7's or Gt-40's (or GT-40P's), an RV cam, an emissions legal Holley from a 351W HO truck, along with some short tube headers and you'll have the guts to move the van. I would recommend at least 3.55 gears.

Another problem is the AOD that locks up in D and OD. This was done to meet the ever stricter EPA MPG requirement during the 80's. Locking up in D allows the engine little room to slip into it's power band and makes the vehicle seem dead.

With OD, you should be getting at least 15mpg highway. Is it running rich? That would contribute to the low power. Honestly, my '64 F250 with 4.56's, no OD, and a 390 gets 9 mpg, you can do better than 10.

I have heard that the emissions hardware doesn't make that much of a difference, but I would remove it if at all possible.