1986 F-250 XLT 6.9 idi C6 switch to 300 4 speed

Finally got started on this project. The truck is in remarkable condition for this area with very little rust.
I am switching out the 6.9 because it doesn't like the cold and I no longer like the noise and smoke and stink.


Project vehicle a couple of years ago - still looks the same. A patch of rust on the roof.


Just don't find trucks in this condition around here


The undercoating is still in good condition


Just about ready to pull the motor

The donor truck is a 1982 extended cab with a 300 and 4 speed, not quite sure which one.
The truck has less than 100,000 miles on it, owned by one family from new and was driven by mature drivers, but it has sat for a couple of years.
I agreed to buy the truck about a month ago but still waiting for the seller to pull his camper off of it!!!
I have not heard it run yet but I am optimistic as I judged the seller to be very honest.
A few decisions to make.
Not sure if I want to go to the expense and trouble of putting the Gear Vendors behind the 4 speed, but it sure would be nice.
I think I will stick with the diesel rad as it is fairly new and all aluminum. It would definitely require a winter front in the cold.
I hope the donor truck has a working tach in it as the diesel tach has about 50 pulses per rev vs 3 for the gas, although may be possible to modify the electronics on it - good arduino project?
Research makes me think that this will be a much easier conversion that going to the 4.9 with the E4OD.
One nice thing about taking apart the old diesel, every thing is covered in an oily film and the fasteners were surprisingly easy to remove.
As far as I can tell the diesel fuel system should be compatible with gasoline, anyone know for sure?
Thanks in advance for any help or suggestions.
Bob - North of North Dakota

Bob,
That looks like a blast to me. Ive been daydreaming about doing the exact same thing.

There is a guy over on full size bronco that converted a bullnose with a 302 and an e40d to a 300 with a zf5 and a hydraulic clutch. His username is "abandonedbronco". He takes good pictures and does good work, it might be woth reading over if you want to see a really clean auto - to - manual conversion.

As for the GVOD - just my two cents. In my bronco, Ive got 3.55s, a slightly moddified 300, and an np435 (1-1 top gear), all on roughly stock diameter tires. When I bought the thing I was convinced I would need to do something for OD.  Ive gotten less and less concerned about it as time goes on. Im at 2000 rpm to make 50 and 2600 for 65. It breathes well a little past 3200ish,but I dont do that much. It makes its best torque around 1500-2000 and the power feels good from 2000-2500ish. So, if you're taking votes, my vote would be to skip the gvod assuming you have 3.55s or 3.73s unless you really want to routinely go faster than 60-65. Mine will happily cruise at 75 on the interstate, I just think its a bad idea for a variety of reasons.

StraightSix, thanks for the encouragement.

Thanks for the heads up on abandonedbronco I took a brief look and there is a lot of good info to work through.

I appreciate your thoughts on the OD. The truck has a 3.55 axle and I am quite happy to cruise at 65. I am a great believer in KISS and also not convinced as to how great the fuel saving would be. I know the fuel economy would increase but I don't believe the GV claims of 20%. It is still going to take as much power to overcome rolling and air resistance so the only saving is on engine friction and then there is the additional loss of the GV OD which although small is still a loss.
You have pretty much convinced me to put it together without the GV and see how it feels. If I really want an OD best to wait until I can locate a ZF5.

Awesome! Im glad I could help.

If Im not mistaken, your 82 probably has a non hydraulic clutch. if so, do you plan to keep it, or convert to hydraulic?

are you interested at all in any engine performance upgrades? if so, there will never be an easier time to swap to EFI exhaust manifolds since you are already going to have to install new exhaust anyways. the only catch is that if you install EFI exhaust manifolds you will either need to go to an aftermarket intake or you will need to make some changes with your factory intake (provide heat source to intake, egr, etc).

if you decide to go with upgrades to your fuel/air induction system, Id be thrilled to send you a parts sheet for the stuff I used. it wouldn't be all inclusive, but I wrote down the part numbers for everything that wasnt trivial to figure out.

John

Hi John, Yes I am sure that the 82 has the mechanical clutch linkage. I will see what kind of condition it is in before I make a decision on that. I don't have the parts to convert to hydraulic so that will encourage me to stick with the mechanical one.

As for the performance upgrades. I do have a 96 EFI 4.9 parts truck and also an unused walker Y pipe so exhaust manifolds for sure.
I don't think that there is an EGR on that engine. I had an 86 F150 with a carbed 4.9 and it had no EGR and no cat converter. Some sort of exemption here in Canada if over a GVWR threshold in those years.
I haven't heard the 300 run yet so once I get some compression and oil pressure readings I will decide how deep into it I want to go. It would be nice to put an Offy intake and a mild cam in it. Will have to wait and see how well the engine runs.

Thanks for the offer on the part numbers, if you have it easily available I would be very interested but don't go out of your way as I am not sure if I will do more than the exhaust manifolds.

Rainy today and so no progress. Hope to pull the old 6.9 on the weekend and also get the transmission out. Snow in the forecast after that so that will put me on hold for a few days as this is an outdoor project. Hopefully by then the donor truck will be here.

Bob

You can also find abandonedbronco information over Ford Truck Enthusiasts in the motor performance area for the six motors.

I run a 300 / NP435 and Advance Adaptor's over drive in my 81 Flare side and a 2.75 rear gear.
Thing is the speed limit here is 70 MPH and if not doing that or more you will get run over!
I can tell you I am turning 1800 in OD @ 70 MPH and that is the same RPM @ 55 MPH in 1:1
Non-OD @ 70 MPH is 2500.
At 75 MPH 2700 RPM non-od / 2000 RPM in od
At 80 MPH 3000 RPM non-od / 2200 RPM in od

I can also tell you my MPG did not change between not using OD and using OD but the lower RPM is less wear on the motor. All my shifting is done below 2000 RM.

I am running EFI exh manifolds into a Walker Ypipe and stock exh system / tail pipe out past the rear tire, no cat.
I do have a heat plate on the factory intake, factory YF carb and air filter assy.

I love the little 300 motor as it pulls good at low RPM and loads of room to work on it.


Dave ----

Hi Dave, thanks very much for the info regarding OD gas mileage that confirms what I was thinking. Nice to save wear on the motor and I am sure it is more pleasant in the cab with the lower engine RPM. The intended use for this truck will not have me screaming down the highway at more than 70 mph so not seeing a huge amount of value added as far as the OD.
I have looked for a dyno graph that gives lbs fuel per hp/hr for the 300 but only found one for a jeep inline six but the curve looked fairly flat up to about 2800rpm so thanks again for confirming that.

I am wondering how much difference do the EFI manifolds make with the YF carburetor and with the coolant heat under the carb how much of a driveability difference during engine warm up.
I too love the low rpm torque of the 300. I put many miles on an 86 F150 with NP 435 and 3.08 rwd and a lot of that was highway miles and an OD would have been nice but it really wasn't an issue. What I really like is the simplicity and low maintenance of the drivetrain, it is pretty much a road going farm tractor.

Bob

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nic55kel wrote

Hi Dave, thanks very much for the info regarding OD gas mileage that confirms what I was thinking. Nice to save wear on the motor and I am sure it is more pleasant in the cab with the lower engine RPM. The intended use for this truck will not have me screaming down the highway at more than 70 mph so not seeing a huge amount of value added as far as the OD.
I have looked for a dyno graph that gives lbs fuel per hp/hr for the 300 but only found one for a jeep inline six but the curve looked fairly flat up to about 2800rpm so thanks again for confirming that.

I am wondering how much difference do the EFI manifolds make with the YF carburetor and with the coolant heat under the carb how much of a driveability difference during engine warm up.
I too love the low rpm torque of the 300. I put many miles on an 86 F150 with NP 435 and 3.08 rwd and a lot of that was highway miles and an OD would have been nice but it really wasn't an issue. What I really like is the simplicity and low maintenance of the drivetrain, it is pretty much a road going farm tractor.

Bob

It is 37 miles each way to work and all but 4 are on the high way of 65 to 70 MPH.

I dontknow how much ther EFI manifolds add as I never drove the truck with out them or the intake heater. I knew I would be driving the truck when it was cold and why I did the coolant heater when rebuilding the truck.

I like that "it is pretty much a road going farm tractor."

ArdWrknTrk wrote

Abandonedbronco is a member here.
You can tag him in your reply to notify him of this thread.  💡

I did not know he was a member on here also.
Dave ----

If you click [assignment] right above the post button you can scroll all the members of the forum.

I saw that username the other day when I tagged Ron (Reamer) about diamond plate rail and gate caps for a Flareside.

"Word on the street" about the intake manifold heat plate is that its fairly important, especially up where you are. My bronco is pretty cold natured after removing the stock exhaust heat to the stock intake manifold. Once it warms up its great, but even in the mild ga winter  (30f mornings are pretty typical) it needs a minute to warm up and get its feet under it.

Ive heard that there can be issues with fuel condensing inside of the intake manifold at really low ambient temps. Ive never seen anything to support that rigorously. What people alledge could happen is liquid fuel running down the manifold toward #6 and lean burn towards #1. Im not sure I beleive all of that,  but it does need warm up time for sure.

I would also think that the water plate could be providing some cooling in hot weather which is more common down here. I had occasion to measure temps in my engine bay with an IR gun a while back and the intake stayed at about 185f consitently after warm up, despite the truck idling for well over an hour and the intake sitting right over the exhaust.

I tell people that are skeptical of my 300 that the bronco is a tractor with highway gears pretty regularly.

Any time you combine a venturi and the latent heat of phase change from a liquid to a vapor things get cold.
These are the laws of thermodynamics and have nothing to do with bias or superstition.

Your sweat evaporates.
It cools you off.
If you wipe yourself down with alcohol it feels even cooler, because alcohol evaporates more readily that saline.

Hold an air tool that uses constant flow on a hot day. (something like a die grinder or DA sander)
That tool is going to get cold.
Pressure drop is responsible.

The same way Bernoulli's principal draws fuel out of a carburetor's jets and boosters.
We have air moving from a higher pressure to a lower pressure. (except this time it is ambient pressure to that of manifold vacuum)

In extreme cases this will lead to humidity actually freezing -carb icing- and this is one of the reasons Ford uses a CWM in the stock air cleaner that should provide a near constant 105°F.

I understand that the manifold requires heat, I have experienced carb icing, when I worked in a nickel mine North of the 55th parallel (nic55kel), and so my concern is more does the coolant heated manifold work as well as the stock configuration?
 
I am retired now and no longer have to drive in all weather conditions so not a major concern but I would expect that the warm up time is longer with the coolant as the source of that heat, just wondering if it is very noticeable.
Has anyone any experience with the coolant heated manifold at around 0 deg F?

As Jim points out maybe the CWM setup pulling air from around the exhaust manifold would be the best solution for a quicker warm up and driveability in cold weather.

Project delayed by weather as it is very wet out and we have snow in the forecast for this weekend.

Bob

It certainly doesn't get hot as fast as having the raw exhaust playing against the intake manifold plenum floor, but it does work as the coolant warms.
And I'm pretty sure that it is bypassing the thermostat.
So it should warm long before the radiator sees any flow.

The heating of the intake from either the stock exh manifold or coolant and the heated air through the air filter do 2 different things.

The hot air through the air filter keeps the carb from icing as it is HOT air going into the carb.

The heating of the intake keeps the air / fuel mix mixed. If you were to cool off the mixture the fuel would drop out of the air and pool on the intake floor and "spill" in to each hole.
Look at compressed air systems, when the air it hot the water stays in it, cool off the air and the water falls out of it. Same happens to the air / fuel mix.
The heated intake keeps this mixture mixed!

Now I run EFI exh manifolds with the factory intake & carb.
I also have the coolant heater for the intake.
As for the heat to the air filter there is no easy way to add the tin to the EFI to capture the heat but have the vacuum hooked up so the flapper should work.
I do have air pulling from down that area of the exh manifolds and from in front of the radiator support.

I have used my truck when in the high 20's wich only a short warm up.
I keep it in the house garage so it is a little warmer, back it out side and let it run while I grab the last few things and turn off lights.
I have only had it sputter 2 times that could have been from the carb icing but not sure?
It is a 2 mile drive from my house to the high way and only 1 light of 3 I get stopped at other wise on the high way for the next 35 miles.

Same when I leave work, fire it up, text wife on my way home and into gear and maybe under 1 miles to the high way if I go that way or then back roads at 45 MPH. I only have 1 light either way before getting on high way or 3 milea before next light andb the motor have some temp in it by that time.

When I did the EFI manifolds I knew I was going to drive it when cold and why the intake heater install.
Dave ----

Okay Dave, thank you for the detailed info. I will make my final decision on that when I am getting the motor ready to install. I will mainly be using the truck spring thru fall and only occasionally in winter so if it takes a little longer to warm up not a big deal. But nice to know it will run properly in the cold just in case it is needed.

I seriously doubt that the sputtering had anything to do with carb ice. When I had it happen it was on a long highway run and it took over an hour to build up. The symptoms were a very noticeable loss of power, I think the conditions of humidity and temperature have to be just right for this to occur as I only experienced it once. When I pulled over the heat of the engine melted the ice and I continued on with no more problem. As I recall it was about 10 below F with high humidity.

This truck will not be a daily driver, probably not go more than 4 - 5000 miles a year. I mainly want it as it is very cheap to insure older trucks here and my 2007 6.0 F250 is way more truck than I need and it doesn't like to sit for more than a week or two. And that 6.0 is a high maintenance engine.

Thanks to all for your inputs.
Bob

I also had to "rig up" hot air for the choke because the EFI manifolds dont have a pass through to get heat from.
I took copper tubing and put a few wraps around 1 of the manifolds and up to the choke, that fresh air side gets hooked were it should also.

As for the stumble it only happened 2 times and it was shortly after I got it on the road for the drive to work. It does not warm up much before I start out and it was as I was pulling up to the light 1/4 mile from my drive. I guess the choke could have pulled off to soon?
Other wise it runs great.
Dave ----

The weather has told me I need to take a break.
The old 6.9 is ready to pull with just the last two bottom bellhousing bolts still in place.



As you can see I am definitely going to need heat on the manifold, the plate to feed coolant to the heat riser pocket looks straightforward to fabricate so will go that route.
I am still waiting to get the donor vehicle so not sure what kind of choke is on it, I am pretty sure that it is an original YF carb with no EGR and no cat converter so the distributor should have the correct advance curve.
By the end of the week the snow should be all gone and things dried up. Hopefully the donor will be ready to pick up by then and I can get back to it.

Bob

Well the seller finally released the truck - had to wait for the ground to dry up some.
I will get it towed home in the next day or two - rear drivers side wheel brake is seized.
Not too surprising as it has sat for probably 4 years.





Temporary fuel tank by washer bottle.



Judging by the condition of the interior and the rolled over odo (in kilometers) the truck appears to have about 70,000 miles on it.

I got it running - started easily  - runs beautifully, no blow by and oil pressure up at the m even when warm, idled nicely and good throttle response. Clutch felt really smooth and the T18 shifted smoothly and felt really solid.

Truck came with a free camper, originally was to have been removed but I think the seller ran out of time. He has sold the farm and has a lot of junk to dispose of quickly.
Not a huge bonus as the camper needs a lot of work, but very salvageable, I am sure that some one will want it.

Anyway excited to be getting the truck home and get moving on this.

Bob