Engine Swap: DOWNGRADE 7.3L idi to 6.9L idi ???

[Tarh331_Dad]

Is it reasonably possible to pull an old high mileage 7.3L idi out of a 1988-1994 F-series Ford Truck, and replace it with a low mileage 6.9L idi from a 1983-1987 F-series Ford Truck?

Or would there be a bunch of adapter plates and adapter rods & whatnot which would have to be fabricated by hand?

From what I've read, in theory the 6.9 and the 7.3 come from exactly the same engine block, with the "only" difference being that Harvester scooped a little more metal out of the block in order to make the higher displacement 7.3.

That's the theory at least, but then there's the reality of whether it would actually work if you tried to do it.

Also, is there anyone who sells remanufactured IDI engines on a regular basis?

I tried searching all over the internet, but I didn't get any good hits on reman'ed IDIs.

Thanks so much!!!

 

[Big Bart]

1) My understanding is the same, the engine can be swapped but there are some considerations around flywheels and pressure plates. Glow plug system is also different, I would use the glow plug system off the 7.3 on the 6.9. There is a current thread about flywheels on this.

T-19/ZF-5 Flywheel

There are a thousand threads on clutches, Flywheels etc.... I need to swap out the clutch on my 86 F-250 6.9. I ordered a Luk Clutch assy. from Parts Geek last night. I did a bunch of searching for what size is in my 6.9. Seems like a 11 inch, but can go up to a 12 inch which I ordered. I...

www.oilburners.net

2) Rebuilders, check out Promar, several here have bought from them.

https://www.promarengine.com/

 

[Old Goat]

They are the same, should just bolt in.
7.3 is a bored out 6.9, with 1/2" head bolts instead of the 7/16".
Uses zd-9 glow plugs instead of the zd-1, and you will have to use the 7.3 GP harness.

Nothing to fabricate to do the change.

Don`t know what part of Gods Country you are in, but up in Wyo. R&R IDI PERFORMANCE and he rebuilds engines.

Custom Engine Builds | R&D IDI PERFORMANCE

R&D IDI Performance | Your source for high quality IDI parts

idiperformance.com

there is Classic Diesel Designs in Texas

Classic Diesel Designs- IDI Performance Parts and Specialists

Classic Diesel Designs is your one stop shop for all things IDI Performance, from performance 7.3 and 6.9 IDI injection pumps and injectors, to custom upgraded performance IDI turbos, turbo kits and intakes, we have over 100 IDI specific products for your classic diesel!

classicdieseldesigns.com

Goat

 

[Cubey]

87 6.9 has the "7.3" glow plugs and controller. if the glow plugs have a blade connector, it's 83-86 style, if bullet then it's 87-94 style.

 

[Tarh331_Dad]

They are the same, should just bolt in.
7.3 is a bored out 6.9, with 1/2" head bolts instead of the 7/16".

Can most diesel shops "precision re-drill" the bolt holes on a 6.9 in order to accept 1/2" bolts, or is that something you should take a specialist?

Or is somebody making some super-hardened 7/16" bolts, which wouldn't need re-drilling?

Thanks.

 

[Tarh331_Dad]

Don`t know what part of Gods Country you are in...

The Vale of Humility between two Mountains of Conceit.

[Although I gotta confess, we're getting swamped by yankee vermin.]

 

[Farmer Rock]

Can most diesel shops "precision re-drill" the bolt holes on a 6.9 in order to accept 1/2" bolts, or is that something you should take a specialist?

Or is somebody making some super-hardened 7/16" bolts, which wouldn't need re-drilling?

Thanks.

From what I understand, if you drill out the 7/16 head bolts to 1/2, you won't be able to completely drill out the old threads to make new clean ones, since the jump in size is only 1/16.


Rock

 

[Jesus Freak]

The Vale of Humility between two Mountains of Conceit.

[Although I gotta confess, we're getting swamped by yankee vermin.]

Yeah, I just read through the "Pilgrims Progress" again. I live in the valley of humiliation myself, and yes Yankees are taking over in humid NW Florida. We'll be California in no time, alas.......
But the swap is straight forward, apply common sense and basic mathimatics and you'll be fine. In theory, except for the head bolts, the 6.9 is probably a better option.

 

[Farmer Rock]

Just go with studs and new gaskets.


Rock

 

[Old Goat]

Can most diesel shops "precision re-drill" the bolt holes on a 6.9 in order to accept 1/2" bolts, or is that something you should take a specialist?

Or is somebody making some super-hardened 7/16" bolts, which wouldn't need re-drilling?

Thanks.

Look in those two links I posted, Justin only shows one set for a 7.3 at R&D.

Wes at Classic Diesel has ARP Studs in stock for a 6.9.

https://classicdieseldesigns.com/collections/engine/products/6-9-idi-arp-head-stud-kit.

It has already been tried by several people to drill out the holes for a larger Head Bolt etc.... not worth the effort.

Goat

 

[FrozenMerc]

As others have stated, it is a bolt in swap, with the exception of the glow plugs. Hell, The motor I just finished building for my '85 F350 is made up of a 7.3 block and pistons, with 6.9 heads and crank.

 

[Nero]

As others have stated, it is a bolt in swap, with the exception of the glow plugs. Hell, The motor I just finished building for my '85 F350 is made up of a 7.3 block and pistons, with 6.9 heads and crank.

Any particular reason for that combo? Just curious.

 

[FrozenMerc]

There is a particular reason. When I discovered the cracked #4 main web on my 6.9, I called a local junk yard that claimed to have a 6.9. Turned out it was really a 7.3 and as it was a core, just the short block, and needed machine work anyways, I just went forward with it. I figured, what the hell, the extra displacement won't hurt me. Though it took quite a bit of welding to get the 6.9 crank to balance correctly with the much heavier 7.3 pistons. The 7.3 crank that was in the junk yard motor was heavily damaged due to a couple of bearings that presumably caused the demise of the motor. My crank guy figured it was going to be cheaper to re-balance and polish the 6.9 crank than rebuild the 7.3 crank.

 

[Jesus Freak]

There is a particular reason. When I discovered the cracked #4 main web on my 6.9, I called a local junk yard that claimed to have a 6.9. Turned out it was really a 7.3 and as it was a core, just the short block, and needed machine work anyways, I just went forward with it. I figured, what the hell, the extra displacement won't hurt me. Though it took quite a bit of welding to get the 6.9 crank to balance correctly with the much heavier 7.3 pistons. The 7.3 crank that was in the junk yard motor was heavily damaged due to a couple of bearings that presumably caused the demise of the motor. My crank guy figured it was going to be cheaper to re-balance and polish the 6.9 crank than rebuild the 7.3 crank.

That's a good reason...

 

[FrozenMerc]

I never said it was a good reason, just the cards I was dealt. Just trying to turn barley into beer. As luck would have it, I found a complete 7.3, just 10 miles from the house about 3 weeks after I got started with the junk yard short block. That engine is now sitting on a rolly cart for now, and all the extra parts from the 6.9/7.3 hermaphrodite build are getting put on the shelf until I am ready to rebuild that motor, which I am thinking may end up in my 1960 Ford C600. The little 332 Lincoln Y Block that is in the C600 now belongs in the front of a hot rod, not in a big truck. A 7.3 IDIT would be a much better fit for that application....

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