Back many years ago, I owned a bone stock 86 F-250 4x4 with a 6.9 and a 4 speed with 3.55's. The truck was never a land rocket, but it definately got around alright even out here in the hills. I rarely had to downshift on long hills, but the truck would lose some speed. I also averaged about 19 MPG.

My fiance's father has an '85 F-250 4x4 with a 6.9, 4 speed and 3.55's. The truck has been converted to a dually and has a pretty heavy steel flatbed on it. It has 168,000 miles on it. He wanted me to do some work to the truck, so I picked it up and drove it over to my shop. This thing is a STONE. It's absolutely pathetic. The truck will go 65mph in 3rd gear and 40mph in 4th! It makes no black smoke whatsoever. It does make a little bit of bluish colored smoke at high RPM, it could probably use some injectors but he doesn't want to throw that much money at it. It starts easily and idles smoothly. The advance in the pump works, I checked it manually. The fuel filter is new. He runs Power Service in it. The engine also seems too quiet to me.. I drive a Cummins now and that thing just barks when you give it fuel. The 6.9 sounds like a gasser with a lifter clack, it's that quiet. I asked what he was getting for mileage and he figured somewhere around 10... When I start out from a start and I put my foot down on it, I can feel the throttle respond only until about halfway down. I hope I described that correctly. It's like the truck accelerates harder as the pedal is applied only to about half throttle. After that point it keeps accelerating at a constant rate until the governor defuels it regardless of how much farther down the pedal is pushed. WTF is wrong with this thing? Did the timing slip or something or is it just REALLY underfueled? Is there anything I can do to help it out at all [don't say turbocharge it ]. Any advice would be appreciated!

 

Sounds like the timing is retarded.
What shape is the air cleaner in?

Sounds like it could also use a little more fuel.

 

Thanks for the reply. The air cleaner is in good shape. How do I go about retiming this engine? I know how to do my Cummins but not a 6.9. Also, how do I turn the fuel up?

 

Timing is set by rotating the IP, top to the passenger side is advance.
All bolts must be tight before the engine is started, IP damage may result if they are not tight.
Small adjustments make a large difference in timing.

I have mine set to the point I have a Power Stroke rattle when the cold start timing advance is on, no rattle when it turns off.
I am happy with that setting.

I advise a pyrometer before adjusting the fuel screw, EGT can get rather high if the fuel is increased.

That said, there is a cover on the passenger side of the IP that looks like a home plate in baseball secured by two screws.
There is also a thin rubber gasket that seals the cover, use care not to tear it as you remove the cover.
Inside there is an allen screw, 3/16" if I remember right.
When the timing mark is at 2:00 position you should be able to see it with a light and mirror.
If you don't see it, rotate the engine 360 degrees.
Turn in is more fuel.
And a little goes a long way with the fuel screw.
Usually I recommend a max of one flat or less on the allen wrench, then drive it to see where you are.
Once you have a light black haze at wide open throttle you have enough fuel.
Any more is wasted fuel, not enough air to burn the fuel completely.

 

Excellent reply. Thanks much, that's exactly what I was looking for. My only question is what exactly is the cold engine advance? Never heard of it before.
It seems pretty straight forward to tinker with this thing. The timing and fuel adjustments are TONS simpler than my Cummins too. I'll have to go ahead and start tweaking on it. I'm not looking to turn it into a sled puller, just improve the drivability. Do these things have much of an issue with EGT? It doesn't have a gauge, but I really can't see an N/A engine get that hot. My Cummins will bury the pyro if I let it, but I have all kinds of stuff done to it. I've nearly doubled the flywheel output of the engine from stock. Maybe I'm way off base?

EDIT: I forgot to ask.. When I checked the air cleaner I noticed that the hole in the bottom of the air cleaner base is about half the size of the engine air intake. Is it common practice to cut the bottom of the base out to help airflow?

 

The IP has a solenoid inside that advances the timing until the coolant reaches about 110 degrees.
Both the timing advance and fast idle are controlled by a switch near the thermostat housing.

EGT can get rather high, even on a NA motor.
Pistons are good for 1250 degrees.

Ford used two styles of air cleaners.
One has a fuul size throat but a lid like this.



The other one has a flat lid, but the bottom air cleaner housing is necked down over the intake throat.

The reason for both was intake noise control.

My original air cleaner was the flat top style, I cut the restriction out and it helped.
Everyone that has the other style cut the "Soup Bowl" off the lid and have noticed improvements.

When increasing the power of an IDI, you add several small improvements together to get more power.
Ram air is another small improvement that does help.
The stock intake is restrictive.

Larger exhaust will also help.

If you want a big single improvement, you add a turbo.

 

Well I guess that answers the air filter question. I'm going to remove the restriction in the base. I never knew there was a cold advance in the pump, makes sense though. The truck has the stock manifolds and y-pipe, but then it goes to 3" pipe with a straight through muffler on it. It's pretty loud and I'm sure it flows better than stock. Do you know offhand if there's a sound clip of a healthy 6.9 on here or elsewhere on the internet. I just want a comparison especially since I'm going to time it by ear. Thanks again!