Max boost idit
Elder User
Joined: May 2018
Posts: 695
Likes: 22
It has nothing to do with connecting rods or rod size. Wrist pin bores in the PISTONS become elongated. Unlike pistons in big diesels, IDI pistons don't have bronze bushings in the bores.
Postmaster
Joined: Dec 2011
Posts: 3,860
Likes: 7
I'd expect all the rotation should happen in the connecting rod end, which *is* bushed.
Now, I suppose it could be a matter of having so much heat/force(from the higher combustion pressures) that it's literally deforming the piston pin hole enough for it to start slapping/bouncing around in there and making itself worse...
That being said, I think the real issue here is that while FoMoCo found this issue on their test stands, we probably aren't running at a high enough power level sustained long enough for this to be a problem...
I certainly haven't heard of worn piston pin hole diameters being a failure mode or problem before.
Lead Driver
Joined: Apr 2008
Posts: 6,938
Likes: 13
I'm trying to figure out why the wrist pins are rotating inside the piston - Is there any reason they need to move at all?
I'd expect all the rotation should happen in the connecting rod end, which *is* bushed.
Now, I suppose it could be a matter of having so much heat/force(from the higher combustion pressures) that it's literally deforming the piston pin hole enough for it to start slapping/bouncing around in there and making itself worse...
That being said, I think the real issue here is that while FoMoCo found this issue on their test stands, we probably aren't running at a high enough power level sustained long enough for this to be a problem...
I certainly haven't heard of worn piston pin hole diameters being a failure mode or problem before.
I'd expect all the rotation should happen in the connecting rod end, which *is* bushed.
Now, I suppose it could be a matter of having so much heat/force(from the higher combustion pressures) that it's literally deforming the piston pin hole enough for it to start slapping/bouncing around in there and making itself worse...
That being said, I think the real issue here is that while FoMoCo found this issue on their test stands, we probably aren't running at a high enough power level sustained long enough for this to be a problem...
I certainly haven't heard of worn piston pin hole diameters being a failure mode or problem before.
Thread Starter
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Senior User
Joined: Jan 2011
Posts: 275
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Pins in IDIs are free floating, the theory is lower wear and resistance. Ive heard a couple other claim this, but i too have never seen proof of such thing. Supposedly in the early 90s some of the puller guys were having issues with the wrist pins ovaling. The psd has the same pins and bare pin bore as IDIT and you never hear of it there either.
but as it was stated before I don't think we are pushing these things that hard. He'll some powerstroke diesel run 40 to 60 psi with weak *** pmr rods
Lead Driver
Joined: Apr 2008
Posts: 6,938
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The cylinder pressure is far higher than the weight of the piston even at unreachable engine speeds. Look at what big blocks spin rpm wise, look what they run for wrist pins as compared to ours. PMR rods are arguably stronger than the forged, but they dont bend, they just let go, which is why most steer clear of them. Either way, ive never heard of an actual wrist pin issue, let alone seen any proof. You have better luck getting a cavitated 7.3, ive seen maybe 3 actual cases.
Elder User
Joined: May 2018
Posts: 695
Likes: 22
Excessive RPM didn't enter into the picture, it was strictly a case of what component would fail over a long period of time (engine hours) when boost was excessive. Back at the time, everyone looked forward to the guy's IDI advice because it was during 6.9's & 7.3's development and research that he was a big part of. With IDI data coming into Ford nationwide there wasn't much he didn't have a handle on. However a few "keyboard mechanics" who never spent a day working in a diesel shop told him he was full of crap just enough times that he dropped out and was never heard from again unfortunately for the rest of us.
Lead Driver
Joined: Apr 2008
Posts: 6,938
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Excessive RPM didn't enter into the picture, it was strictly a case of what component would fail over a long period of time (engine hours) when boost was excessive. Back at the time, everyone looked forward to the guy's IDI advice because it was during 6.9's & 7.3's development and research that he was a big part of. With IDI data coming into Ford nationwide there wasn't much he didn't have a handle on. However a few "keyboard mechanics" who never spent a day working in a diesel shop told him he was full of crap just enough times that he dropped out and was never heard from again unfortunately for the rest of us.
i ain't rite
Joined: Mar 2005
Posts: 65,443
Likes: 5,517
From: Marlboro Mental Hospital.
but it was posted on the internet, so IT HAS TO BE TRUE!!!
that sounds like something "powerstroke help dude" would say.
that sounds like something "powerstroke help dude" would say.
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Senior User
Joined: Jan 2011
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Yea theres no shortage of people running their mouths with no knowledge or experience, especailly on the IDI boards. Im not saying the guy was wrong, but there are thousands of IDIs out there with turbos that came from the factory with the 28mm wrist pin. I own 3 of them, one had an ATS put on it when it was literally brand new and did nothing but tow a 6 horse trailer for 240k miles, another had a turbo on it from very early in life and pulled a big fifthwheel everytime it moved, and the third is one i put a turbo on, and beat the holy hell out of. My 79 had an hx 35, far too small, but spooled at like 1300 rpm, i drove the crap out of it, talk about cylinder pressure, 18psi at 1500 rpm? None of mine had the slightest piston wear, nor even were the wrist pins out of round. Granted thats just mine, but out of the other thousands of idi's with turbos and the fact that nobody has ever had to deal with this issue? Lets just say i was skeptical about the guys advice.
I think it was mention before there is just not enough example of truck running at higher than factory boost numbers to know 100% where the failure rate is
Tuned
Joined: Jul 2010
Posts: 435
Likes: 6
From: Kitimat British columbia
As far as know factory engine in my truck. At least factory turbo engine. No head studs or upgraded valve spring. My trucks rolls around without me in it 7960 lbs without a full tank of fuel. Have hit well pased 20 a few times no gasket failures yet pyro in dp hasnt seen more than 700. Intercoolerd from a e350 6.0 some tweaking to fit. Much better ones can be put in. S360 turbo was suppose to be a s366 according to the part number but someone messed up rebuilding it. .91 t4 housing 3 inch dp to 4 inch exhaust turbo ip maxed out. Enough jam to snap a dana 60 axle u joint. Shoot for 300 to 350 rwhp and you will be more than happy. Should last quick awhile but service life is shortened just be ready for it
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Senior User
Joined: Jan 2011
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As far as know factory engine in my truck. At least factory turbo engine. No head studs or upgraded valve spring. My trucks rolls around without me in it 7960 lbs without a full tank of fuel. Have hit well pased 20 a few times no gasket failures yet pyro in dp hasnt seen more than 700. Intercoolerd from a e350 6.0 some tweaking to fit. Much better ones can be put in. S360 turbo was suppose to be a s366 according to the part number but someone messed up rebuilding it. .91 t4 housing 3 inch dp to 4 inch exhaust turbo ip maxed out. Enough jam to snap a dana 60 axle u joint. Shoot for 300 to 350 rwhp and you will be more than happy. Should last quick awhile but service life is shortened just be ready for it
are you just a maxed out stock pump
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Senior User
Joined: Jan 2011
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do it yourself or buy one
Lead Driver
Joined: Apr 2008
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It was in my 79, so i built a custom up pipe setup to mimic the first gen banks. Basically cut right after the Y and ran it up the bellhousing. Even with the wastegate removed IE, its open all the time, actuator off the turbo, it still made insane backpressure, would spool at 1400rpm and be dead on its face 1400* by 2600. The 12cm housing with the little bitty turbine is just too small for a 7.3. The compressor is decent-ish, just a poor trim for a larger engine with lower boost, but you need at least a 40 turbine and a 17cm housing. HX 35 made 200rwhp on an idi with a 110 pump, a banks or 093 will do 240+ if tuned.
Lead Driver
Joined: Apr 2008
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.91 T4 Flows great and is responsive, especially with the 68mm turbine, though i wouldnt run the 68 with a compressor larger than the 62 (it can be had with the 64.5, but its surgy on larger engines)