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1985 6.9 Diesel rebuild/overhaul

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Old 10-09-2011, 10:14 AM
Brettboat Brettboat is offline
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1985 6.9 Diesel rebuild/overhaul

Hey guys, I have a 1985 6.9 IDI diesel in an E350 that I'm wanting to swap into another truck and I figured with the 370,000 miles on it currently that I'd break it down and buy a rebuild kit. That being said, what's the differnce between the 6.9 and 7.3? Couldnt I just buy a 7.3 rebuild kit for the 6.9 and add a little displacement? Because correct me if I'm wrong, but isnt the displacement differnce between 6.9 and 7.3 all in the stroke as apose to bore I.D.?

Or is it more complex than that and not worth doing?
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Old 10-09-2011, 10:56 AM
MN6.9Diesel MN6.9Diesel is offline
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From what i understand the difference is only in the bore. When they changed from the 6.9 to the 7.3 the bore got changed from 4.00'' in the 6.9 to 4.11'' in the 7.3 with the stroke remaining the same. I also have a 6.9 and have read many mixed reviews on people trying to swap parts over from a 7.3. If i were you'd i'd stick with the 6.9 and keep the .11'' of cylinder wall thickness. Just my two cents.
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Old 10-09-2011, 11:10 AM
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I've read that there MAY be a balance issue and that the head bolts are larger (something I could get a machineshop to do)...
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Old 10-09-2011, 02:01 PM
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A 7.3 is a bored out 6.9 0.110 over. That's all it is.


Is the cylinder bores show wear, bore it out at the minimum. That will leave room for maybe another rebuilt in the future. Because a 7.3 cannot be bored over as the cylinder walls are already to thin.



If your going to swap this van engine into a truck, you will need a truck drivers side exhaust manifolds. They are not the same.
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Old 10-09-2011, 04:58 PM
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These engines are known for high mileage. I'd hate to put all that time effort and money into a truck and have it run EXACTLY the same! Maybe money would be better spent on a new Injection pump an injectors... or better yet get a turbo for it.
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Old 10-09-2011, 06:07 PM
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rebuild the bottom end and hone the cylinders and put new rings on if the cylinders are in decent shape ! if you can port and polish the heads and tweak the IP pump and get a good set of injectors !
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Old 10-09-2011, 08:51 PM
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Put on new valve springs also while into it. Also cant put bigger head bolts in a 6.9 block.
Hone, new rings and bearings, turque cam, turbo and rebuilt pump new injectors and hammer down,
and the van oil cooler is also different than truck.
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Old 10-09-2011, 09:40 PM
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It ran great until the starter went out 4 years ago... It's just been sitting and because of the downturn in the economy I've never been able to justify replacing it because we have a 3 other, nicer and faster 7.3 and 6.0 (POS) Powerstrokes.

I only want to rebuild it because I want to drop it in my F150 after I do my Dana 60 swap. Figured it'd be nice to bacicly have a more or less "new" 6.9 under my hood. I'd like to do a few after market things. Turbo, upgraded injector pump, stage 1 injectors, etc... Hopfully push that 300HP mark.
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Old 10-09-2011, 11:28 PM
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If you want to push 300 hp do the things that type4 said at the very minimum. Also along with that you will need head studs and a turbo that will push 20 psi without superheating the air. Also check out the build threads over at Powerstroke Nation. NMB2 is going pretty extreme with his build and RacinNdrummin is going to hit about the level you want to hit. NMB2 started a thread here on his build but it was started later in the build. But anyway check it out. It will be of interest to you.
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Old 10-09-2011, 11:58 PM
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Yea, I read that the stock bolts like to give with "high boost"... I saw some head studs from dps-performance with what they say to be "220,000psi tensile strength"...
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Old 10-10-2011, 02:11 PM
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Arp has some stud also that are pretty cheap for the 6.9. Dps has some good fuel products but I have heard of a few people that have said that their studs from Dps snapped when they were taking the out. One of the people was icanfixall over at OB. But idk, they might have gotten better studs now. Also, if you are looking for more performance you can't go wrong with their fuel products. I love my stage 1s.
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