First long distrance trip after major mods

[nilknarf007]

A little history. Steeped in ignorance, I did a smog delete on a purchased 1985 F150 4x4 with a 4.9 I6. Before delete, 11 mpg. After delete, 11 mpg with no power. Received a ton of help on this forum, and replaced the feedback YFA carb with a non-feedback YF. Also put in an HEI distributor/ignition with vacuum advance. Ran much better, and was able to advance the timing - currently set a 10 BTDC.

I was excited because I knew I had a long distance trip in my future, 600+ miles round trip. Halfway through the trip, I realized I had created another problem, also due to ignorance. I screwed up the PCV system, blocked all the wrong stuff, and found that oil was being sprayed (quite a bit of oil) into the air cleaner.

I figured that out once I got home, and hooked everything back up the way it is supposed to be. No more oil in the air cleaner.

End result before the PCV was fixed - 14 MPG. Not as good as I was expecting, but certainly better than before. I'm hoping that now I've solved the PCV thing, I may get a little better than the 14 MPG.

The new carb and ignition also took care of the problem of not being able to go up hillsbecause of a lack of power. As a matter of fact, on this whole trip, I only thought about the hill problem on two occasions, and only because I had no issues. At highway speeds, the truck went right up the hills with no bogging or decrease in speed.

Thank you all that helped me through this process. Now onto the next thing, the clutch......

[Gary Lewis]

Congrat's! You should be proud!

But, you should be getting a bit better MPG, like maybe 17ish? (I realize you have 4wd and no overdrive, so I've backed it down a bit from David/1986F150Six's ~20 MPG.) I suspect that you will need to advance the initial spark timing a bit to get there, and may need to play with the vacuum advance. But I'd start dialing in a bit more timing, like 12 or 14 BTDC. If you get kickback on starting then drop back a bit.

[Sac79]

Glad to hear you had a safe and almost uneventful trip!

Do you mind sharing how you messed up the PCV system? I'm in the process of sorting mine out and would like to avoid any mistakes.

I also think you should be able to get better mileage. I got around 14-15mpg with my truck while it was also running in 'system cut to pieces' mode... Then again, I don't know all the circumstances, if you were doing 75mph on the interstate then I think 14mpg is quite good, or at least I would be happy with that.

[FuzzFace2]

Glad to hear you had a safe and almost uneventful trip!

Do you mind sharing how you messed up the PCV system? I'm in the process of sorting mine out and would like to avoid any mistakes.

I also think you should be able to get better mileage. I got around 14-15mpg with my truck while it was also running in 'system cut to pieces' mode... Then again, I don't know all the circumstances, if you were doing 75mph on the interstate then I think 14mpg is quite good, or at least I would be happy with that.

If it made the trip out & back on its own that is a good thing

Now on the MPG issue. How fast were you going, do you know what gear ratios you have and what size tires? Do you know if the speedo is on the money?

My 81 F100 4x2 with 300 / T18 (granny gear trans)with 2.75 rear gear is getting mid 14's but that is 30 miles high way at 65 MPH to work and 45 MPH with a few lights the 30 miles on streets.

I have not done anything to get the MPG higher just yet and my speedo is on the money.

Dave ----

[nilknarf007]

If it made the trip out & back on its own that is a good thing

Now on the MPG issue. How fast were you going, do you know what gear ratios you have and what size tires? Do you know if the speedo is on the money?

My 81 F100 4x2 with 300 / T18 (granny gear trans)with 2.75 rear gear is getting mid 14's but that is 30 miles high way at 65 MPH to work and 45 MPH with a few lights the 30 miles on streets.

I have not done anything to get the MPG higher just yet and my speedo is on the money.

Dave ----

I have a complicated answer for all of that. My rear end is 3.55 (I think). I found that near the top of the chunk that faces the front of the truck.

My stock tires were 245/70R15. That gave me 65 MPH at 2400 RPM. The tires I have on there now are 285/75R16. That means when my speedo is at 60, I'm actually doing 70.3 MPH. So for the interstate, I kept it between 65 and 75 of actual speed, always staying below 2350. I use a speedometer app on my phone to track the actual mileage since that is also messed up by the bigger tires.

[nilknarf007]

Glad to hear you had a safe and almost uneventful trip!

Do you mind sharing how you messed up the PCV system? I'm in the process of sorting mine out and would like to avoid any mistakes.

I also think you should be able to get better mileage. I got around 14-15mpg with my truck while it was also running in 'system cut to pieces' mode... Then again, I don't know all the circumstances, if you were doing 75mph on the interstate then I think 14mpg is quite good, or at least I would be happy with that.

As far as messing up the PCV, keep in mind this was out of complete ignorance. I simply plugged the PCV valve at the rear of my valve cover. On the vent in the front, I put one of those aftermarket vents. This caused me to spray oil all over my valve cover.

I stopped at an autozone to figure it out, and the guy told me the vent should be going to the air cleaner. So we figured out some tubing to get from the vent to the air cleaner. The guy told me that the verticle distance traveled from the valve cover to the air cleaner would prevent oil from making it to the carb.

WRONG! My air filter was quickly ruined, and I went through a quart of oil in 300 miles. This was no good, and obviously something was very wrong.

By plugging the PCV valve, I reversed the air flow. The positive crankcase pressure was blowing through the aftermarket vent, thus oil going everywhere. The PCV valve should be hooked up to the bottom of the carb, the vacuum pulling at the PCV valve. So the vent at the front of the valve cover should be sucking air in, not blowing it out.

I got everything hooked up correctly, cleaned up the oil, and replaced the air filter. I've run about 50 miles since then, and everything is clean as a whistle.

[nilknarf007]

Congrat's! You should be proud!

But, you should be getting a bit better MPG, like maybe 17ish? (I realize you have 4wd and no overdrive, so I've backed it down a bit from David/1986F150Six's ~20 MPG.) I suspect that you will need to advance the initial spark timing a bit to get there, and may need to play with the vacuum advance. But I'd start dialing in a bit more timing, like 12 or 14 BTDC. If you get kickback on starting then drop back a bit.

Gary, I am thinking of advancing the timing just a hair more. But, I bet if I ran at the 55 MPH the truck was designed to do, I'd get better mileage. The Bullnose is a brick pushing through the air, so just because I can go faster with the same RPMs due to the bigger tires, the drag is increasing exponentially. At least now I can make the one way trip on two tanks of gase instead of almost three!

[Sac79]

As far as messing up the PCV, keep in mind this was out of complete ignorance. I simply plugged the PCV valve at the rear of my valve cover. On the vent in the front, I put one of those aftermarket vents. This caused me to spray oil all over my valve cover.

I stopped at an autozone to figure it out, and the guy told me the vent should be going to the air cleaner. So we figured out some tubing to get from the vent to the air cleaner. The guy told me that the verticle distance traveled from the valve cover to the air cleaner would prevent oil from making it to the carb.

WRONG! My air filter was quickly ruined, and I went through a quart of oil in 300 miles. This was no good, and obviously something was very wrong.

By plugging the PCV valve, I reversed the air flow. The positive crankcase pressure was blowing through the aftermarket vent, thus oil going everywhere. The PCV valve should be hooked up to the bottom of the carb, the vacuum pulling at the PCV valve. So the vent at the front of the valve cover should be sucking air in, not blowing it out.

I got everything hooked up correctly, cleaned up the oil, and replaced the air filter. I've run about 50 miles since then, and everything is clean as a whistle.

No harm no foul? Well a couple of filters and some oil I guess for a story to tell and laugh about. I might have done the same without the guidance of the other members on here. The lack of knowledge at some local parts stores is kinda sad though.

As for the mileage, with your bigger wheels, it's probably not terrible. We'll see what the experts say... David? I'm planning on going with similar sized wheels, maybe 275/75, also on 16s, and I would be happy with 15mpg at 70mph. I have 3.08 ratio though, which makes yours even more acceptable to me.

[nilknarf007]

No harm no foul? Well a couple of filters and some oil I guess for a story to tell and laugh about. I might have done the same without the guidance of the other members on here. The lack of knowledge at some local parts stores is kinda sad though.

As for the mileage, with your bigger wheels, it's probably not terrible. We'll see what the experts say... David? I'm planning on going with similar sized wheels, maybe 275/75, also on 16s, and I would be happy with 15mpg at 70mph. I have 3.08 ratio though, which makes yours even more acceptable to me.

Sac79, it turns out I have the 3.08 rear end also....

[Sac79]

Sac79, it turns out I have the 3.08 rear end also....

Still sounds good to me. Maybe you'll get an opportunity to test it again, on something other than an interstate at 55-60mph? I bet you'll get closer to 17-18mpg... Anyway, enjoy the smooth driving!