I have a 1995 F150 4x4, 351, auto tranny. Over the past couple of years, my gas mileage has slowly dropped off, last time I gassed up I was getting 9.4 mpg in town. I am leaking a small ammount of anti-freeze from somewhere along the mating surface of the drivers side head, it pools up just outboard of the distributer and I need to top off the overflow reservoir about once a month. When i change my plugs, my number 1 plug is always fouled (dark, gummy deposits around the lead), while my other plugs look more normal.
I have changed the fuel filter, plugs, plug wires, distributer cap & rotor, and coil recently.
I'm trying to regain some gas mileage. I plan on tearing down the upper end of the engine and replacing all the gaskets (including head gaskets) and sensors, cleaning the heads and intake, and putting it back together. I have 8 new injectors and pressure regulator that I will swap out while I'm in there.
Should this do the trick, restoring some power and raising my mileage? Is there anything else that I'm overlooking or not taking into consideration?
Any input is appreciated. Thanks
Steve

 

Could the gummy deposits on your #1 plug be from the leaking antifreeze?

As far as improving mileage, I think you have covered all the bases. Run some good cleaner through the gas prior to tearing down to break loose any more gunk before you put new components in. Other than the things you have mentioned, I'm not sure what else could be giving you bad mileage. I guess it wouldn't hurt to replace the O2 sensors and clean your EGR and IAC valves while you at it. Let us know how it turns out.

-Chris

 

Thanks for the reply!
If I'm leaving the bottom end alone, should I bother working the heads at all? I was going to take them to a shop and have them tanked and checked for cracks, but that was about it. I am kicking around the idea of replacing the stock manifolds with a set of shorty headers that would fit to stock y-pipes, is that just a waste of money or would it help the engine at all.
And finally I was going to add a K&N air intake system, as I've heard that they do have proven power gains. What about fuel eficiency? Power is always good, but the combination of less than 10 mpg and the current cost of gas has me thinking a bit more economically. My main goal is to turn the reigns on this fuel consumption without dropping in a smaller engine!
Steve

 

headers help the motor breathe better. As for fuel economy it might hurt you because you might really like the increased performance




Jim

 

I'll take that as a green light for the headers I was concerned that shorties wouldn't do anything, and I don't want to screw with full length headers right now. What are your thoughts on maybe upgrading to 1.7 rockers? I've read other posts where people swear by performance gains of a 351 with these. If you were to swap out the rockers, should you do the pushrods and lifters too, or can you re-use the old?

 

long tubes will give you more low end torque. as for the rockers I'm not sure cause I've just kept mine stock. You might want to upgrade to an efan if you haven't done so already. An efan eliminates drag on the motor from the stock clutch fan



Jim

 

Agreed on the electric fan. I'm planning on doing that upgrade real soon, I have heard a lot of positive results from guys on here. As for the roller rockers, same thing. I still have stock rockers but I've heard that upgrading can show some increased performance, although you might see a decrease in mileage, not too sure. Good luck.

-Chris

 

let me get this straight:

you are leaking/losing anti freeze, you have a plug that fouls out regularly, you do not want to get into the engine but you want more performance and think adding headers and e-fan will give you added gas mileage.

the last person i knew who did just the top end ended up having bad rings and had to replace the engine anyway.

you need to stand back and ask yourself exactly what you need to do before you go dumping a bunch of money on things that you do not need until the engine is fixed.

imho, quicklook2

 

I agree. I was a little confused after I posted my first post recommending places to look for fixing your mileage and your truck in general, but then you were looking for more performance? Quicklook's giving good advice, make sure you're truck is running the way you want it before you start beefin it up.

-Chris

 

Thanks for the reality check guys. Its easy to start getting carried away in the pages of the Summit magazine and lose track of what got you into the book to start with...
Yes, the main thing I want to do is figure out why my mileage is bottoming out. If my rings were leaking by, wouldn't I be passing blue smoke through the exhaust? The only wierd exhaust I notice is white, and it clears up once the engine is warmed up; and its only prevalent in the colder months. I'm tending to think that I'm getting anti-freeze in the combustion chamber, which is why I want to replace the head gaskets. I'm not burning too much oil, I only really notice it if I'm towing anything on the highway. Is there any way to check for ring leakage without a compression tester?

 

get the compression checked.

get a vacuum gauge and read the insructions that come with it.

it will tell you a wholes lot of info on your engine.