6.9l to 7.3l IDI Swap

[My9373]

So I've recently really fell in love with the '86-style fords (is that the "slantnose" style?) and now have my eyes peeled for them on Craigs. My question is, I'm not too familiar with the 6.9's only the 7.3's from experience, and was wondering what the pro's and con's are to the 6.9 and how are they power, performance and dependability wise in comparison with the 7.3's? I'm thinking if I can find one I like with a 6.9 maybe high mileage or something, I'll find a deal on a 7.3 and just swap the 7.3 in an probably the e40d, as it's gotta be automatic and I do some highway driving too. If that's the case, how hard and how involved is a 6.9>7.3 swap? Theres actually an '86 in my area, lariat, xlt, ext. cab, 4x4 with a plow setup, (condition is hard to tell from crummy pics, cannot see fenders well enough to notice rust) and claims to run great just needs gone, $1500, that ALREADY has a 7.3 swap in it. Is it basically a simple swap or very involved?

Thanks guys

 

[bghnkinf350]

Simple swap between the two. With that said, why would you for the extra 24 - 25 inches? The 6.9's are stouter blocks with thicker walls. The only downfall is the smaller head bolts, but that is not much of a problem.

 

[Kevin 007]

SticK with the 6.9!!! I wish my 1990 7.3 was a 6.9.
The 7.3's had valve guide issues due to the lack of lubrication past the valve seals whcih are too tight, the 6.9 had different seals which allowed more oil to pass. They didn't have guide issues.

the 7.3 was more prone to cavitation than the 6.9.

Just re-torque your 6.9 head bolts (which is factory recommended anyways) and roll on and enjoy. You won't notice a big power difference if you upgrade to the 7.3

 

[92F350CC]

and the head bolts can be replaced with head studs if you're planning to run high boost.

Also, the 6.9's don't overheat as easily as the 7.3, because of a coolant passage that is present in the 6.9 head, but was blocked in the 7.3 head. I think the only disadvantage to a 6.9 is they use a little oil....
Should be an almost direct swap however. There are only minor differences.

 

[icanfixall]

Both of these idi engines will swap with only a bolt in application. The engine blocks and heads are all drilled alike so its just unbolt and bolt in another engine no matter it be a 6.9 or 7.3. The parts that wont swap over are the van oil coolers and drivers side exhaust manifold. So if your using a van engine to replace a truck engine you need to only remove those two pieces. Then bolt it into the truck or van. Just depends which way your moving the engine... Most will agree the hp and torque is about 10 hp differance between the 6.9 or 7.3. The 6.9 has a weak set of 7/16 head bolts but... A set of ARP studs will cure that issue. The 7.3 is known for weak cylinders. They move during combustion creating cavitation. There is no known amount of miles when this happens. A few engines have several hundred thousand miles on them and never an issue to. Others have issues at 50,000 miles. Its a guessing game. Both engines share all the same internals in the non turbo style. So you are able to install 6.9 rods in a 7.3 or go the other way.Even the part numbers are the same..

 

[My9373]

WOW guys that was really informative in less than an hour! Awesome, so that all being said, I don't think I would touch the 6.9 then if I found one, I'll just look for a nicer low mileage one with a long life ahead of it. 10hp, I could care less about, that could be compensated for with little tweaks. Did the 86-era models offer the e4od or just the c4? I've never owned a c4 before only the e4od but would rather have the overdrive at higher speeds, such as needing to take the highway, etc. Thanks again guys

 

[bghnkinf350]

Do a ZF5 swap instead of the e4od. Cheaper to do and better trans. Or throw in a GV.

 

[Ididriver]

Do a ZF5 swap instead of the e4od. Cheaper to do and better trans. Or throw in a GV.

I think he said it had to be an auto

 

[92F350CC]

The 6.9 was only available with the C6(I believe is the diesel version of the C4) and T19. I think you could get it with a ZF-5 in 87. The E4OD didn't come out until 89 or 90. If you want to put an E4OD in it, make sure it's freshened up and if possible, modified. They are known to fail.

 

[Jbevs]

The '86 sounds like a good truck for the price. Especially if its a 350. The only downfall IMO of the 6.9 is the glowplug system which was changed in the '87 models and stayed through the 7.3 years.

 

[My9373]

Yeah, if I could, a ZF5 would be my first choice, but unfortunately, even though I'm only 20, I've already had a knee replacement on my clutch leg and can't manage a clutch for extended rides now But I'm sure the C6 (thanks for that correction, idk where I was going with C4) would suffice, unless I could find a deal on an e4od and have it built. Does GV make an overdrive unit for the C6? All i really care about is the truck being able to run 70-80mph on the highway at respectable RPMs. If the C6 is capable, the e4od issue is out the window.

I'll definitely keep my eye on that '86 for sale and ask for some more pictures too.

And also, tell me more about this GP system, whats the issues with it and can it be swapped easily to the newer post-'87 system?

Thanks

 

[Jbevs]

It's somewhat easily swapped out to the 7.3 type. The problem with the 6.9 type is when it fails, it fails with the gp's on, burning them all out.

 

[bghnkinf350]

The C6 is capable, and GV makes a unit for them. You would not have the most fuel efficient truck with a C6 though unless you did a gear swap and/or add a GV.

 

[My9373]

Cool so I would just swap the system then.

What kind of mpgs could be expected with a 6.9/C6 stock? Fuel efficiency isn't major concern considering my current vehicle but improvements don't hurt.

 

[icanfixall]

Gear Vendors and adapters are found on ebay all the time. The Jmodel is the older one soget the P models. Parts are easier to find.