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LOL!!! You think I'll say it is too long of a post???? Silly boy. You just have a lot to share. And, a good job doing it.
Yes, I think the next thing to do is to give the vacuum advance two more turns, which will bring the advance in a bit earlier - probably 2" earlier. And, I say 2 turns as one turn will probably on bring it in 1" earlier and I doubt that little change will be noticed. Then if the 2 turns gets pinging at light throttle just turn it back one turn. And if it doesn't, then give it 2 more turns. We want to get it to ping just a bit so we know where the edge of the envelope is and then back off.
But, stepping back and looking at the data, if you throw out the tank where we did the testing, inc WOT, and average the other two tanks you get 22.37 MPG for the trip up and 22.50 for the trip back. That's pretty close, but it might say it is a bit better. On the other hand you were running in rain coming up and in the clear on the way back. But, as you said, you might have run slightly faster on the way back. Bottom line: We fixed two problems (pinging under WOT and kicking back on starting) and didn't hurt the MPG.
I will wait to make the vacuum advance adjustment [+2 turns clockwise] until this tank is completed. I want to see if the in-town mileage average has been affected by the changes made over the weekend.
I want to point out that with the addition of the factory chin spoiler [see list above with "*"], the next tank representing in-town mileage improved. Only one data point is not enough, but when you add that to the fact that on this trip [with chin spoiler] the truck achieved two 23+ mpg tanks, which in 6+ years has never achieved greater than 22 mpg. It looks like the spoiler actually helps with gas mileage.
Good plan, Stan. Make the tests scientific. But, I'm betting that we helped the in-town mileage as we brought the vacuum advance in earlier/kept it in lower in the vacuum curve. So you are running more timing everywhere but at really heavy throttle, which you don't do.
In fact, you are already feeling the effects of that timing advance as you said the engine runs easier or more freely. That means you are able to back off the throttle a bit, which means you have more vacuum, which means you have more advance, which......... So that has to show up in the MPG. Right?
I do not have a photo, Ken. I had hoped it would show in the photo you cited. Perhaps when Gary comes back online, he can provide the part number. He has a NOS one to install on Dad's Truck.
At home, I can get the number, but it will be tomorrow.
The chin spoiler is "L" shaped with one leg of the "L" hanging down and is mounted utilizing the 6 1/4" holes located on the bottom of the bumper. It measures approximately 1" deep and 48" long centered relative to the bumper. It is made of black plastic and is beveled on each end.
P.S. Ken, I just looked again at the OK GTG photo and the spoiler can be seen. It is not large... look again with the description above and you will see it.
FORD must have thought it worked as it was on the high MPG models. My son's 1984 F150 with 4.9L, 4 speed manual O.D. and 2.47 rear gears came with one.
Last edited by 1986F150six; 09-16-2014 at 02:28 PM.
Reason: Post script to Ken after looking at the photo.
Guess you haven't watched the Myth Busters episode on tailgates:
The Myth: Driving with your pickup truck's tailgate down is more fuel efficient than driving with your tailgate up. Additionally, driving with no tailgate at all, with a hard cover over the pickup bed, or with mesh in place of the tailgate is more fuel efficient than driving with your tailgate up.
The Test: Jamie and Adam test all of these pickup myths by measuring the fuel efficiency of each method while driving on a straight road at 55 mph.
The Result: Driving with the tailgate down increases the drag and thus is less fuel efficient than driving with the tailgate up. The closed tailgate creates a vortex in the bed of the truck that allows for smoother flow of air than when the tailgate is down and the vortex is dispersed. This myth is busted. However, upon their revisit to the myth in a later episode, the mesh proves to be the most fuel-efficient method, while no tailgate, the hard-cover top and the tailgate up prove to be about the same fuel efficient.
P.S. Ken, I just looked again at the OK GTG photo and the spoiler can be seen. It is not large... look again with the description above and you will see it.
Thanks David.....I did see that strip but thought I was seeing a chassis cross member, back behind the bumper.
I wonder why the deflectors weren't more universally installed, particularly on lighter (higher speed) trucks?
The fact that the catalog uses the term "fuel economy" in the description of the front air dam got me to wondering how many other uses of the term there are in the catalog. Looks like in addition to the air dam these things were different for the fuel economy package:
Engine - there was a different part number for the engine itself
The following is from memory, so I cannot cite a reference [sorry, Chris! ], but I once read that the 300/4.9L camshaft for trucks equipped with 2.47 and 2.70 differentials was different than those with higher ratios. I suppose, if correct, it would be ground for more low end torque.
NumberDummy, please shed some light on this question! Thank you!
G. L.
Yes I did see that episode in part. What you and others don't remember is that they used a newer pickup that has much better aerodynamics than the BRICK S&^%H*#$@ aerodynamics of the 60's, 70's, and early 80's pickups. People use to get anywhere from 0.5 - 2.0 MPG better with I6's (240/300) thru 460 V8's. This in the 70's and 80's before I bought my first diesel.
You may not agree with me and that's OK. Always take TV shows with 6 grains of salt.
09-15-2014, 03:30 PM
Silly boy. You just have a lot to share. And, a good job doing it. 
], but I once read that the 300/4.9L camshaft for trucks equipped with 2.47 and 2.70 differentials was different than those with higher ratios. I suppose, if correct, it would be ground for more low end torque.
