Wrist pin failure questions

[BuffaloGuy]

My motor just cratered after about 30,000 miles on a fresh rebuild. All eight of the wrist pin bushings have turned in their seats. Some have turned a full 180 degrees. Some have even started to slip out. Some are chipped.

My question is this: How common is wrist pin/ wrist bushing failure in these motors?

What are the reasons this could have happened?

Any insight would be appreciated.

[john8662]

I'd call Avant and ask them why the engine they built is having these issues. I've seen an engine lately that really had a loose wrist pin disassembled. There was a score line on the side of the cylinder where the pin in the piston was. I don't know how common this problem is, but I suspect thats the problem with my engine too.

Maybe when the engine was rebuilt the "re-conditioned" rods were not correctly re-conditioned and or the wrong bushings were installing leaving the wrist pins too tight. If they're too tight they will cause the busings to spin.

I am leaning really hard towards replacing the rods when I R&R my engine, I recently saw the results of re-used rods in a new engine build up with new everything. One rod broke off completly below the piston, then the rest was scrap metal.

[ 12-17-2004, 03:21 PM: Message edited by: john8662 ]

[Billman]

The 6.5TD has Full-Floating Wrist Pins?

[gmctd]

Some lowered compression pistons are created by over-sizing the piston pin bores, installing offset bushings - lowers the entire piston up to 0.100".

Would seem to work in a low-rpm motor.

Izzat the case here? Dunno.......

[eracers999]

It failed for 1 of a few select reasons.

1. The bushings were not installed correctly.
2. The bushing clearance to pin, too tight, this is a very precision measurement. Rod, pin, everything has to be the same temp.
3. Lack of lubrication either by you running it out of oil, or the bushing clearance too tight to lube properly.
There is very few that i trust to do rod work.

Kent

[BuffaloGuy]

Thanks for the feedback guys. The motor was built to stock compression. It never ran out of oil nor has it been overheated. The heat tabs on the block show the hottest it had gotten was about 215F.

The cylinders were not scored and mic'd out fine. The crank is slightly under spec but fairly smooth. I'm pretty disapointed that the crank was under spec. With only 30,000 on it it should not be under spec.

It's looking like a wrist pin failure is most commonly associated with improper installation vs. use or abuse.

I was injecting washer fluid that day which will increase HP and decrease EGT and IT. My temps were all running just great.

I wouldn't think that the slightly more hp from the water/methanol mix would stress it. Heck, the added HP from LP injection has to be way more than a little methanol.

I'm wondering if the wrist pin bushings were in wrong from the start. Would they hold up for this long if they were in wrong from the start?

The wrist pins are splash oiled and there is a small oil port on the bushing that, when installed correctely, lines up with a corresponding port on the rod and allows oil into the area.

Not one of mine were lined up.

After calling around and doing searches on TDP it seems that wrist pin failure is pretty rare with these motors. Am I right?

Ken

[john8662]

Was this the engine built by Avant?

So are these wrist pins splash oiled or are the oiled through passages in the rod?

[78Chev]

Also, Ken, did your engine sound like the recording john8662 posted a while back? Mine does and I'm curious if I'm looking at wrist pin problems too.
Randy

[dieseldummy]

When I overhauled my engine all but two of my wrist pin bushings were out of spec. It cost around $115 for parts to get them plus labor to install them. My guess is that most "reconditioned" rods probably don't get new ones...
Justin

[LucasEnglish]

If you can heaer the extra rattle from the alc than that can cause extream cylinder pressure. Like to much inj adv you lower egt but raise cylender pressure. I have been told by some one who played with water and alc a few yers ago that thay made there rist pins go bad form using to much alc. I only run straight water in my setup. I know it makes better power with the alc. Drops me form a 17.2-16.5 on the g-tech with alc insted of water, But the motor does not sound happy.

[Kennedy]

They are always black and blue when removed after service, but I've never seen them spin in the rods. My guess is that the press fit may have been incorrect, and they spun eclipsing the oil holes, OR were not lined up properly when installed. If they spun, it should show evidence of galling on the rod and bushing backing. I think it would be pretty darn hard for the smooth finish of the pin to grab the bushing.

One other alternative is IF the ebngine was run under severe detonation, it could have pounded things up, but again, the softer bearing material should have taken the pounding. I'd have to look at one again, but I'm pretty sure these have a steel backing...

[BuffaloGuy]

John8662:
They are splash oiled only. Yes, it was an Avant rebuild.

78 Chev:
My motor did sound like the sound clip that John8662 posted but it's hard to say for sure. Mine got worse pretty fast.

LucasEnglish:
I doubt that the little bit of methanol that is in this washer fluid could hurt. It freezes solid at zero (even though it says it's good to -20F). I'll bet that it only has 20% or less methanol. From what I hear, that is way less than half of what most guys run. The increased rattle is hardly noticeable.

JK:
We haven't pulled the bushings themselves yet. I'm betting that the tolerances were not correct on installation. No severe detonation either. The increased rattle is way less than even when the cold advance feature on the IP is on. When it was injecting the untrained ear wouldn't even notice the difference in sound.

I guess I'll see how Avant handles this.

[john8662]

The Buffalo Guy,

Keep us posted on what Avant does or says caused this situation. I was really about to purchase a set of pistons with re-conditioned rods for my 6.5L rebuild from Avant. Now, I might just have my local machine shop recondition my rods.

My noise got worse too, it was somewhat inconsistant and got worse. The engine is still in the burb, although the intake and valve covers are off while I was looking for something "simple".
I'm hoping to get the engine pulled sometime this month.

78 Chev,

I've noticed a similar but totally different sounds on my 6.2L diesel, I think its normal, especially non-turbo. The turbo obsorbs tons of the odd noises on these engines. I'll be quite interested to see how my 6.2 in my 86 sounds and runs now with new gears and a new injection pump (no more dern rebuilds!!!).

[Jim P]

I bored the wristpin bushings on my engine myself. I bored them .010" off center to lower the compression. .010 is about all you can go with stock bushings because they only have about .025" stock in them for finish machining. I left about .002" stock when I bored them and then I had them honed to size. The bushings are indeed steel backed and they take considerable pressure to press these into the rods. I find it hard to believe that they could spin in the rods. The oil holes in my new bushings were considerably smaller than the hole in the rods so I drilled the bushings out to match the oil hole size in the rod.