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6.9L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 6.9 Liter In-Direct Injection Navistar engines.

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post #1 of 9 (permalink) Old 07-06-2008, 11:48 PM Thread Starter
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bent connecting rod

well i got the motor out of my 85 6.9l and the conclusion was a bent rod and the piston was broke around the pin. I'm Really suprised it didn't break rod or shatter piston.

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post #2 of 9 (permalink) Old 07-07-2008, 11:44 PM
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What did you do to this engine?
You are surprised that there was not more damage!

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post #3 of 9 (permalink) Old 07-08-2008, 12:27 AM Thread Starter
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i drove through a swamp and ingested quite a bit a water. then i drove it around for a year in that condition so i am suprised that it didn't do more damage. My buddy figures that the cylinder might be out of round a little bit because of the extra stess from the bent rod. Is that possible. And if so is there a way to find out with out me going out and having to buy a feeler gauge or micrometer. I'm going to get new piston rings and connecting rod and put motor back together. There is some rust in the other three cylinders but i'm gonna turn it upside down and clean it out with lots of diesel fuel and maybe a real fine sand paper.

2004 CREW CAB PSD, no mods, 305/70/16R wrangler MTR.
1985 ford f-250 4x4 6.9l sc "the beast"
4" lift, 35" toyo mud terrain's, Ip turned up, stacks
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post #4 of 9 (permalink) Old 07-08-2008, 08:53 AM
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bent rod

hello there is no other way to check for out of round ans taper, other than a inside dia bore gage these are not costly around 35.00 for a set from 1.00 to 6.00 dia and a dial vernier caliper at a parts store will get you to within one one thousands of an inch (.oo1) ok? if the rod was bent and the wrist pin area of piston was cracked or broke it more than likely scraped up the wall some you can rent a flex hone a a auto parts stoe and clean up the cylinder this wont tru up the dia much but it will help check the dia and make sure your not going to have to use an oversive piston and ring set
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post #5 of 9 (permalink) Old 07-08-2008, 11:25 AM
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If you're rebuilding your own engine, you better have your own micrometer and snap gauge set (or dial bore gauge like mentioned above, but that's more money). If you want your engine to last at all, you MUST check all of the clearances, and repair anything that's out of spec.

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post #6 of 9 (permalink) Old 07-08-2008, 08:40 PM Thread Starter
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my buddy has a plastigauge i'm gonna use. There is suprisingly no scratches at all on the cylinder walls. but i wanna make sure it is still perfectly cylindrical

2004 CREW CAB PSD, no mods, 305/70/16R wrangler MTR.
1985 ford f-250 4x4 6.9l sc "the beast"
4" lift, 35" toyo mud terrain's, Ip turned up, stacks
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post #7 of 9 (permalink) Old 07-08-2008, 08:56 PM
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Originally Posted by hougie View Post
my buddy has a plastigauge i'm gonna use.
As far as I know plastigauge is only used for bearing clearances. You need to use a set of calipers/mics to check the cylinder for out of roundness.

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post #8 of 9 (permalink) Old 07-08-2008, 11:13 PM
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Take the block to a machine shop. Most will be able to measure the bore and tell you if it's okay. Also, you need to check crank journals, head condition, valve guides / seats, etc.

It's enough work to rebuild one of these, you may as well do it right. It really really REALLY sucks having to rebuild a motor you just worked on, trust me. And it's even worse when you're stuck by the side of the road because you did a half-***ed job of rebuilding. I know this from experience. It is not fun.

Just do it right. You'll be happy later.

BTW, pm me if you need a rod still. I have 7 good used ones. (had a set, but needed one to replace the bent one after ^....)

85 F250 4x4 w/ 6.9 diesel, ZF5 trans, custom wastegated turbo, rebuilt engine (twice) exhaust brake and lots of other stuff. Noisy, ugly and most of the time it even all works.
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post #9 of 9 (permalink) Old 07-08-2008, 11:49 PM
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Any rod from either a 6.9 or 7.3 non turbo motor will work for you. They are exactlly the same part number. The piston is differant from these 2 motors. No cylinder is perfectly round. You can measure it down to the millionth and find it out of round. It all depends on where you want to stop the measurement. If its within 1/2 of a thousands I would say thats perfect. They don't come closer than that from the factory. You can look at the wear pattern and tell if its bad. Checking the crank is going to be the important area. Look at the bearing wear. If its worn off to copper on one side or the other you know which way the bend made it wear. The space between the rods on the crank is 0.012 to 0.024. The rod bearing on the crank is 2.5001 to 2.5016 wide. The running clearance on the rod bearing to crank is 0.0011 to 0.0036. The rod bolt torque is step one, 38 lbs. The step 2 is 51 lbs.

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