6.9 & 7.3 Interchangeability
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6.9 & 7.3 Interchangeability
I am not much into later model Ford stuff, or any diesel junk for that matter...but I have a possible job, and need some info. A coworker has an 88 f250 with a 6.9 and a 4 spd. He wants that motor put in his 92 f350, 7.3 5 spd. Do these motors interchange that easily? He has heard they will. What about flywheels? exhaust mani's? Also, do the injection pump/injectors swap? He just had a new pump and injectors put on the 7.3 before it crapped, and would like to use them if possible. BTW, the 7.3 is NON turbo.
Now I know, the 6.9 would be a down grade, but he has a good solid double cab one ton truck, and he wants that truck to run. He isn't worried about the difference in power between the motors, he just needs his one ton back on the road.
ROb
Now I know, the 6.9 would be a down grade, but he has a good solid double cab one ton truck, and he wants that truck to run. He isn't worried about the difference in power between the motors, he just needs his one ton back on the road.
ROb
Lead Driver
Joined: Nov 2003
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From: Campbell River, B.C.
Actually overall the 6.9 is the better engine stock for stock. Thicker cylinder walls mean that cavatation is not nearly as much an issue and the 6.9 can be reliably rebuild and rebored if necessary several times during the life of the block. The 7.3 block cannot be safely overbored because it is basically a 6.9 block bored out and is too thin. I would sooner recomment swapping a 7.3 IDI for a 6.9 than the other way around.
Externally, the motors are identical. Everything will bolt up. Manifolds (there is a difference between vans and trucks though), fuel system, accessories, flywheel, and so on. Internally most of the parts will still interchange.
Only major weakness the 6.9 has is the head bolts that can make it less reliable if you want to put over 10 psi of boost in it for turbo applications. If its left stock its not an issue though and stronger bolts are available if it is.
Externally, the motors are identical. Everything will bolt up. Manifolds (there is a difference between vans and trucks though), fuel system, accessories, flywheel, and so on. Internally most of the parts will still interchange.
Only major weakness the 6.9 has is the head bolts that can make it less reliable if you want to put over 10 psi of boost in it for turbo applications. If its left stock its not an issue though and stronger bolts are available if it is.
Laughing Gas
Joined: Mar 2006
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From: Fitzpatrick Alabama
Simple bolt in, 88 model trucks had 7.3 engins. If the 88 is an automatic, All you have to do is remove the engine, swap the flywheel and clutch, and put it back. The Injectors and injection pump will swap. You need to see whether the 88 is a 7.3 or 6.9, if it is a 6.9 it has been swapped. The wiring may be different, but what I did was take the wiring harness off the engines and swap them since where the engines plugged in was different. I swapped the whole wiring harness, basically anything that was on the old engine went with the new one. The wiring harness needs to stay in whatever truck it came in, if it is a 6.9 you may need to swap the glow plugs since it has a different glow plug system. I would also recommend putting new MOTOCRAFT brand glowplugs in it. If it is a 7.3 in the 88 which I strongly suspect, it will be the same wires and everything. The way to tell is to see if the oil fill tube is made on with a cover below it, or if the oil fill tube is removable, in which case it will have two bolts at the bottom where it comes off. The made on oil tube is a 7.3 and the removable is a 6.9.
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From: Troy MT
i wouldent swap the pumps unless you take the pump your putting on the " good " motor to a fuels shop and have it reset for the 6.9 or the 7.3.
the 6.9 pump on the 7.3 will run lean ( easy fix, turn it up ) the 7.3 pump on the 6.9 it will chirp rattle and bang like its about to blow
the 6.9 pump on the 7.3 will run lean ( easy fix, turn it up ) the 7.3 pump on the 6.9 it will chirp rattle and bang like its about to blow
Postmaster
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From: Sweet Home, OR
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I will have him check for sure on the motor. The 250 may be an 87 model, I don't remember for sure now...It is standard shift truck though, so will the flywheels need to be swapped? Someone mentioned the injector pump needing tweaked to swap to the 6.9, but are the injectors the same, or the glowplugs?
Thanks
ROb
Thanks
ROb
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Elder User
Joined: Sep 2007
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From: Huntsville, TX
As far as I can tell, the injectors will swap over. I recommend getting a new install kit for the injectors. You may nick an oring and that injector will leak.
The glow plug systems are different between the 6.9 and the 7.3, may need some fine tuning, but if you just do like Andy said if you swap it all then you should be fine.
The glow plug systems are different between the 6.9 and the 7.3, may need some fine tuning, but if you just do like Andy said if you swap it all then you should be fine.
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
On NA motors, any of the IP's will work fine.
But say you are running an 88 IP, you should also be running 88 injectors.
Likewise if you run an 85 IP, the injectors should also be from an 85 engine.
93 and 94 turbo IP's will usually put out to much fuel for a NA motor.
But say you are running an 88 IP, you should also be running 88 injectors.
Likewise if you run an 85 IP, the injectors should also be from an 85 engine.
93 and 94 turbo IP's will usually put out to much fuel for a NA motor.
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Well, this is good news. I need to find out for sure the year on the donor truck though...But I still don't know about flywheel interchangeability. He had a new pump and injectors installed on the 7.3 before it crapped, and he was wanting to somewhat recoop the cost of that, but oh well. The 7.3 actually still runs, but he said it makes an awful sort of racket, so he is figurin it is time for the swap.
ROb
ROb