Learn me about the 6.9/7.3 idi motors

NorthernWoodsman

Adventurer/tinkerer
I've narrowed my search for a camping vehicle option down to a full-size truck w/TC. No surprise but costs for anything labelled Cummins or Powerstroke have skyrocketed. That's fine, I like older trucks anyway, right? I had an '88 F150 2WD that I sold to buy my first 4WD, a 1985 Toyota RCLB with the 22R and solid front axle. Don't regret that move, but I always had a soft spot for that Ford. Had the 302 w/5spd., an extra cab big enough to easily sleep in, and big a$$ captain chairs...but it wasn't 4WD so he had to go.

Fast forward and I'm back to looking at Ford (my preference) and looking at the 87-91 era trucks. This is in part due to my previous F-series, but also because the first 4x4 I fell in love with was the Turtle III. I recently found a 1987 F250 RCLB, 4WD, 7.3L diesel. I thought they moved to the 7.3L in 87, but have seen conflicting info as some 87 trucks are listed with the 6.9L, others with the 7.3L. Anyhow, this is a one owner truck, has the 5spd trans, never wrecked, 220k miles. Downsides to me are the manual trans (I prefer an auto these days) and the blue interior (really Ford, blue and red interiors? :sick:). The paint is pretty crusty, read lots of surface rust, err, patina, which I actually like, keeps peoples eyes from lingering too long. No cancer, just surface crust. I've already nicknamed it the Barnacle.

But really I'm curious about these motors. I've read about the cavitation issues and what needed to be done to maintain the motors, especially prior to 150k if possible. I know they're not Powerstroke fast and powerful and you can't tune them to that sort of power, which is fine, I prefer slow and steady over driving a 4wd Ferrari. Besides, for road trips involving hotels or Air BnB I have a 2016 Tacoma TRD OR double-cab that goes fast enough for me. The Barnacle would be more for hauling a camper big enough for me (6'4") and tooling along on a road trips to get outdoors, enjoy backroads, dirt roads, and the off beaten paths.

What say you? Are they good motors worth owning if they've been cared for? How do they do hauling a camper? Can some upgrades like new exhaust and, possibly, a Banks turbo kit help much? What else is there to watch out for on these era trucks and motors?

Oh, did I mention the price? $3800 OBO. And I'm getting close to selling my 1994 Toyota 4x4 pickup, ha! Coming full circle, kind of.

*Edit- Almost forgot the two trucks on here that inspired me to look into older trucks:

Larry's K10: https://expeditionportal.com/forum/threads/larrys-1978-k10.56355/
Rot Box's F350 (Can't find a build thread for his truck)
 
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arveetek

Adventurer
They are very reliable, simple engines. Adding a turbo will help tremendously, especially when traveling to higher elevations where the oxygen thins out. The glow plug relays are notorious for failing, causing hard start issues, but is a simple repair. The cavitation issue is probably their weakest link.

An old IDI like that would make the perfect apocalypse vehicle! Only needs one wire to keep the engine running (fuel solenoid on the injection pump). No electronics or computers to worry about.

Casey
 

NorthernWoodsman

Adventurer/tinkerer
Figured the turbo was key since I've seen quite a few with refits over the years. Sounds like cavitation isn't really that bad of an issue...if it was caught in time, otherwise it's a boat anchor. And yes, just watched season 8 of The Walking Dead so gotta think about outrunning those zombies.

They are very reliable, simple engines. Adding a turbo will help tremendously, especially when traveling to higher elevations where the oxygen thins out. The glow plug relays are notorious for failing, causing hard start issues, but is a simple repair. The cavitation issue is probably their weakest link.

An old IDI like that would make the perfect apocalypse vehicle! Only needs one wire to keep the engine running (fuel solenoid on the injection pump). No electronics or computers to worry about.

Casey
How slow? And compared to what? A Powerstroke or Cummins inter-cooled turbo-diesels? The truck I'm looking at is the 7.3L. But why not a 6.9L? Same engine and I've heard the 6.9L has thicker walls so is preferred by some.

Reliable and SLOW.

As stated above they need a turbo added.

Would not bother with a 6.9 at all.
 
If it's been well cared for I'd pick it up. Worst case is you need a reman long block, of which there are plenty. Idi won't get you the efficiency of a di engine, but it won't cost nearly as much. And super easy to work on.
 

NorthernWoodsman

Adventurer/tinkerer
I assume by efficiency you're referring to mpg's? Reports online aren't terrible - 15-24 depending on loaded or unloaded/ties/gears/etc. I cannot afford anything stamped Powerstroke or Cummins these days, I see absolute junk being sold for ludicrous prices now. Simple, slow, old...it's the truck version of me!

If it's been well cared for I'd pick it up. Worst case is you need a reman long block, of which there are plenty. Idi won't get you the efficiency of a di engine, but it won't cost nearly as much. And super easy to work on.
 

NatersXJ6

Explorer
Slow. If you live in a place with no freeways no problem... if you live in California you will be “Number 1” to most people here. You’ll feel any altitude changes. But really reliable, with the ability to run in a partially impaired condition, no limp-home mode there... For $3800...? That market died here. I tried to sell a well-built and banks turbocharged 6.2 Chevy a few years ago and couldn’t get $4k. I would say offer $3k and wait until the seller sees the light.
 

vintageracer

To Infinity and Beyond!
The newest 6.9 was installed in a 1987 model Ford PU Truck. It didn't last long for a reason. The 7.3 was a better engine. The newest 7.3 IDI was installed in a 1994 model Ford PU Truck. Nothing wrong with old.

I see 1995-1997 Powerstroke DI F250-F350 for sale all the time for $3K and less. Rough? Not exactly nice however affordable. 4WD adds cost however you already new that!

460 equipped trucks pull much better (More Power) than the IDI equipped Ford Diesel truck at the expense of fuel economy however you can buy a 460 crew cab 4WD F350 PU all day in good condition for $5K or less if you look. A lot less headaches with the 460, gas is way cheaper than diesel and maintenance is a lot less with a gasser.

A 5 Speed equipped IDI truck will be more drive-able and get better MPG due to overdrive and better gear splits than an automatic equipped truck. The automatic is only a 3 speed until either 90 or 91 in the diesel. The dual mass flywheel on 7.3 5 speed Manual transmission trucks can be problematic. Most have been replaced by now.

The truck you describe in your OP is about as good as it will get in a 7.3 IDI without a turbo. Adding a turbo to the above truck is expensive and makes your cheap truck expensive You probably will not like towing the BIG TRAILER that you describe with an IDI non turbo 7.3 however you did say SLOW IS GOOD!


https://en.wikipedia.org/wiki/International_Harvester_IDI
 

NorthernWoodsman

Adventurer/tinkerer
There is no way on earth you're getting a Powerstroke 4x4 for $3k or less in my neck o the woods. I see piles of dog $hit going for $7-10k all day long. Decent to very good condition and we're talking $10-20k for a 20+ year old truck. It's absurd.

The truck I'm looking at is an 87 model, but owner says it's the 7.3L. The inter webs seems conflicting as to whether or not the 87 model year had the 7.3 or the 6.9 or both.

I have zero interest in a gasser. 5-8mpg's is not attractive no matter how you spin it. And I never mentioned towing a BIG TRAILER. I want to add a camper. Huge difference in weight there.

Turbo kits brand new are only $2.5k. On a $3k truck I don't really see that as making my truck "expensive". Better, yes.


The newest 6.9 was installed in a 1987 model Ford PU Truck. It didn't last long for a reason. The 7.3 was a better engine. The newest 7.3 IDI was installed in a 1994 model Ford PU Truck. Nothing wrong with old.

I see 1995-1997 Powerstroke DI F250-F350 for sale all the time for $3K and less. Rough? Not exactly nice however affordable. 4WD adds cost however you already new that!

460 equipped trucks pull much better (More Power) than the IDI equipped Ford Diesel truck at the expense of fuel economy however you can buy a 460 crew cab 4WD F350 PU all day in good condition for $5K or less if you look. A lot less headaches with the 460, gas is way cheaper than diesel and maintenance is a lot less with a gasser.

A 5 Speed equipped IDI truck will be more drive-able and get better MPG due to overdrive and better gear splits than an automatic equipped truck. The automatic is only a 3 speed until either 90 or 91 in the diesel. The dual mass flywheel on 7.3 5 speed Manual transmission trucks can be problematic. Most have been replaced by now.

The truck you describe in your OP is about as good as it will get in a 7.3 IDI without a turbo. Adding a turbo to the above truck is expensive and makes your cheap truck expensive You probably will not like towing the BIG TRAILER that you describe with an IDI non turbo 7.3 however you did say SLOW IS GOOD!


https://en.wikipedia.org/wiki/International_Harvester_IDI
 
I've been running 6.5s for the past 20 years. With a turbo installed they become much more useful for towing. I don't see the higher maintenance cost that people typically mention. Oil, filters, really no different than gas prices.
 

Pangle

Wanderer
If I got another IDI i would take it straight to R&D if I lived on the west coast, otherwise i would order a turbo Kit from them with their turbo also.
 

NorthernWoodsman

Adventurer/tinkerer
I've been running 6.5s for the past 20 years. With a turbo installed they become much more useful for towing. I don't see the higher maintenance cost that people typically mention. Oil, filters, really no different than gas prices.
Thanks vintageracer, good to hear from someone who's running one of these older diesels. I know it's never gonna be a 500hp, 1000ft. lbs of torque monster, and am thankful for that. It's funny that I'll see people on here drool over old Toyota's (which I love) with diesel or weak gassers and not seem to care a bit about the low power or slowness. But as soon as you start talking full-size trucks, everyone compares them to a new diesel and craps on the old ones.

If I got another IDI i would take it straight to R&D if I lived on the west coast, otherwise i would order a turbo Kit from them with their turbo also.
Pangle, thanks for that link! I was just researching turbo kits and parts last night. R&D looks to make some really nice stuff. *EDIT*- and they're not even that far from me!

Buy a flight, hop in, drive home. No rusty Midwest truck. https://fortcollins.craigslist.org/cto/d/94-fpowertroke/6689794697.html
Well, needs tires and a carrier bearing, neither a big deal.
But, a powerstroke is where the cheap maintenance ends compared to an idi. That's the big attraction of the IDI, simple and cheap. Who knows too, that PS above might be hammered, and not a wise purchase.
Aww man, I did not need to be tempted like this. I haven't been able to find an F350 in the extra-cab/longbed or even RCLB versions. CCCLB is too much truck for my wants, but the price, color and 350 size is hard to look past. Guess I'm spending part of this weekend looking at craigslist outside my area....dangit!
 
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UHAULER

Explorer
I've had two, an 84 6.9 with a c6 auto, no overdrive and 4.10 gears. slow,gutless with the auto trans. Later I had a 93 7.3 with the 5 speed, much better but still really lost power in the mountains. Both were reliable and cheap to maintain. I agree with you on the prices of trucks with a powerstroke, everybody thinks they are gold. 99-02 beaters with high miles for 7,000-14,000. All I see with a high miles beater is dollar signs to maintain and repair.
I'm actually thinking about doing something similar, an f250 or 350 with a camper but have been looking at either a 460 or a v10.
 
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