1986 6.9 in a 70's F-250 or F-350...

[TBigLug]

Well, it's getting warmer so my project bug is getting the better of me. I'm thinking of taking the 6.9 and C6 out of my '86 and putting it in a 70's extended cab F-250 or F-350 then putting the gasser in my '86 and selling it. Couple of questions to those who have done it.

What is the frame width difference between the 70's and 80's trucks?
Which motor mounts can I use?
What's the difference between the C6's used in a divorced t-case application and the 2WD?
Which years had the divorced cases and which had the married cases?
Did the 70's trucks use galvanized fuel tanks (aka bad for diesel fuel)?
Will a 460 radiator be big enough for the 6.9?

Here's my thoughts...

It should be fairly straight forward. Pull the motors out of both trucks. Drop the 6.9 into teh 70's truck. Build some kind of stub shaft to go from the back of my C6 to the divorced case. Shifter linkage and accelerator linkage would probably have to be modified to work on the 6.9. Replace the original tank with a plastic one. Plumb my water seperator in somewhere along the fuel line. Install an electric lift pump since the 460 would have a mechanical one on the block. Install my glow plug solenoid with a manual push button. Putting the gasser in the '86 should be even easier since I'd leave it carb'd. My main concern would be getting the diesel in the older truck. I love the 70's bodystyle and I thiknk with the 6.9 in it it would get good enough fuel mileage to still be my DD and the 4x4 and probably 4.10's would make it a great hauler. Throw some load range E 33's on it, a gooseneck ball in the bed and roll out.

Any ideas or thoughts, I'm all ears. I think there'd be more room in the engine compartment for adding a turbo later on. Regardless it'd be cool as hell.

 

[GOOSE]

Awesome build platform!

Man, you're onto a dream build of mine. I do not have domensions but have both vintage trucks I can pull measurements off of if need be. The diesel motor mounts have two studs compared to the gassers one. 2wd and divorced C6 are the same. I would seriously look into a different trans, one with an overdrive. The divorced setup makes your options almost limitless, the 6.9 has a SAE #3 bell pattern behind the ford adapter plate. Allison, E4OD, air shift manual, great platform for flexibility. With 4:10's and C6 the truck will get poor economy and max out at 65mph.

If I am right, pre 77 1/2 Fords had FE big blocks, drum front brakes, closed knuckle front ends,(4wd) and divorced t cases. 77 1/2 introduced the M block, basically a smog motor, married trans/ t cases and open knuckle dana 44 hd fronts with disc brakes. 460's are almost a bolt in swap for the m blocks, same bell bolt pattern. This is for f250's. Camper specials and some snow plow prepped trucks had Dana 60's. This summary is based on 3/4 ton 4x4's.

I have seen plastic front tanks and metal rear tanks. Don't think they are galvinized on inside. Keep in mind diesels need return lines and this vintage did not have that setup.

Based on your desire to tow a gooseneck and add a turbo later, make sure the 460 radiator has at least as much surface area and as many rows in it. I have seen big honkin' bus radiators fit in these trucks, 6.9 rad will probably bolt in with a few holes drilled.

460 and 6.9 have mechanical fuel pumps so the electric one will be an option rather than a necessity.

The logger in my signature gets 15mpg to and from work and so close to 20mpg's on highway. An overdrive trans should net you close to this. Yes, the 73-79 is my favorite bodystyle as well. This is a very worthwile build if you ask me.

 

[TBigLug]

My main reason for going with the C6 is merely based on what I have available. I never go over 60 mph anyway and it already nets 17-21 mpg in my current truck (3/4 ton 2WD 3.54 gear) so I figure even if it drops down to 15 it's still high enough to justify it being a daily driver. I'd appreciate it if some time you could grab the frame width dimensions for me. I'm curious to see how differant they really are. So 77 is the cut-off for divorced t-cases. That helps me narrow down my search alot. I'll probably swap out the front axle for one from a later model with disc brakes. I should be able to mock up some return lines without much trouble. Especially if I stick to one large tank in the rear.

I also remember that the F-600 front clips are SUPPOSED to bolt right on to these cabs. Maybe that's another thought, bolt on the F-600 clip and net even more room in the engine compartment. I'll have a flatbed on the rear most likely so I shouldn't have to worry about the front end being out of proportion. It would also make room for a HUGE radiator.

Hmmm, I hear some gears turning in my head...

 

[grog85]

I may be wrong, but I thought 73 and later had disc fronts, or is that just the 2wd?

 

[bike-maker]

A F600 front clip will bolt on to a standard cab, but it takes some changes. F600 cabs have about a 3" body lift built into them. So a body lift to the cab would be required. This gives you the extra room to run a medium duty tranny using that SAE bolt pattern that goose mentioned - tons of options there. Steering column / firewall and trans hump are different. Steering column/trans hump is a mute point, firewall is the one that counts because the F600 hood (which is the same hood as a pickup) is mounted to the firewall instead of the fender. That part would take a little bit of work. You would get a BIG radiator out of the deal. And it will take some huge tires to fill those wheel wells.

 

[TBigLug]

Hmm, good point. I've been looking at pictures of the 600's and i think I'll stick with a standard truck front clip.

 

[GOOSE]

Early 77 still had the divorced setup. These are referred to as high boys, usually fit 36 inch tires stock. Late 77 or 77 1/2 went to low boy setup.

Yes, 2wd pickups had front discs throught the 70's.

I did notice that you were working with the parts you have available, definitly understand this. Should have measurements early next week, my 77 is not at my house right now. It will be easy to stick with the Dana 44hd or early D60. The 86 and up D60's have a totally different steering layout. A similar vintage box may be necessary if you're taking this route. Also the front diff is placed in the 70's truck in a manner that may require a lift and lowering the bump stops to clear the lower end of the idi.

Edit: the highboys may not have this issue.

 

[TBigLug]

Sounds lik a '77 High Boy wuld be right up my alley since I want to run 235/85R16's in the winter and somewhere around a 315/75R16 in the summer.

 

[papastruck]

Your frame width on the dentside trucks is going to be determined by what style you have. The frames on the highboys are narrower - I think by 4 inches. I've never seen any highboy extended cab, but I could be wrong that they don't exist. 78-79 4 by extended cabs should have the updated wider frame and married transfer case setup, and that would likely be the easiest vintage for you. I saw a '78 on ebay a couple years ago while looking for my dentside which had the 7.3 IDI and a ZF in it. Went for close to 5 digits. 2wd extended cabs were available before '78 and seem much more common, but converting that era to 4wd is not for the faint of heart, as you have to relocate the steering box from behind the axle to the front.

Sorry - you were asking for first hand responses, but I thought I'd chime in as an owner of that vintage and someone who wanted to do the same thing, in case it aids your research. Hope to see pics of this build soon!

 

[TBigLug]

Tht does help. My main interest in the pre '77 was just based on the availability of the divorced tansfer case. Would make it easier to drop my whole powertrain into the truck. Extendd cab, not a necessity. I could deal with a stadard cab. I hadn't thought about the steering geometries and such as far as the 2WD to 4WD conversions would go. It's hard when you don't have a truck of that vintage in front of me to compare. I appreciate the input from people who own them or have owned them. Keep the info coming.

 

[GOOSE]

I measured the motor mounts and to no surprise the diesel's are wider. A 351M engine mounting studs are 16.5" apart. The lower studs on an IDI are 19.5" apart. I would say this is most relavant on 77.5-79 trucks as these ones had the M block. I do believe the high-boy frames are 34 inches wide and the 77.5 and up ones are 37.5 inches. These are rear frame measurements. I do not have the high-boy vintage to measure off of, sorry

 

[TBigLug]

No problem. Those measurements will help. 1.5 inches wouldn't be too hard to add to each side I don't think. The plot thickens...

 

[opusd2]

I have the SAME truck, an early 77 Highboy with the dog 351 and was considering dropping my 6.9 into it. I'm still in the discovery phases of planning tho'

 

[TBigLug]

I have the SAME truck, an early 77 Highboy with the dog 351 and was considering dropping my 6.9 into it. I'm still in the discovery phases of planning tho'

You've definitely come to the right place!

 

[opusd2]

Yeah, I've read a few threads on it here and on a couple of other sites, but I have yet to dig into my truck's physical dimensions to read what I think I will need to get it done.

It's awesome that I have the divorced transfer case, that will definitely help! But I am still torn between going with the automatic I have on my 6.9 right now, or go with the standard in my 77. I have a bad leg from an accident which hurts when clutching, and will have to have a car seat for my little guy in the truck, which is why I am leaning to the auto way of things.

Plus I have plenty of 70's for truck parts at home