PING: Ian

Ian, I checked your website related to the 3.1/3.8L GM engines. Nice pics. I am curious about the pistons you had pictures of...what's the story behind those?

Reply to
Anthony
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"Anthony" wrote

They are just a comparison of a new piston and a scuffed piston from the 3100 engine. We replace lots of pistons on these engines for noise when cold.

Ian

Reply to
shiden_kai

"shiden_kai" wrote in news:cKL1b.20346$ snipped-for-privacy@news2.telusplanet.net:

Hehe...I'll bet. There is a good reason for that, but I'll not elaborate on it in public. I will say that there was nothing wrong with the pistons.

Reply to
Anthony

"Anthony" wrote

My mistake....I had a look at those pictures again, and there is no "new" piston in the pictures. Please elaborate on your theory that there was nothing wrong with some of those pistons. Don't worry about it being a public forum. GM would be happy to know that there is nothing wrong with the scuffed pistons that are almost an epidemic in their 3100 engines. Then they wouldn't have to replace so many pistons.

Ian

Reply to
shiden_kai

Post it here! Bob

Reply to
Bob

Anthony wrote in news:Xns93E16B382AA8acziparle3sp835@65.82.44.187:

Final-Recipient: RFC822; Action: failed Status: 5.1.1 Remote-MTA: dns; mx3.hotmail.com (65.54.253.99) Diagnostic-Code: smtp; 550 Requested action not taken: mailbox unavailable

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Reply to
Anthony

"Bob" wrote in news: snipped-for-privacy@corp.supernews.com:

To clarify, there was nothing wrong with the piston design or manufacture. There are other problems with this engine and the piston damage you see is a result of those problems. I cannot elaborate further without potentially putting my job on the line, and for my family's sake, i'm not going to do that.

Reply to
Anthony

"Anthony" wrote

That e-mail address you see isn't valid (of course).

Just post here, you won't be hurting mine or GM's feelings if you think that there was nothing wrong with "some" of those pistons.

Ian

Reply to
shiden_kai

Sounds like a conspiracy theory to me. Fill in the blanks:

"To clarify, there was nothing wrong with (_____________) or manufacture. There are other problems with this (_______) and the (________) damage you see is a result of those problems. I cannot elaborate further without potentially putting my job on the line, and for my family's sake, i'm not going to do that."

Sorry, but this has my conspiracy theorist alarms all going off. You can take the above statement and adapt it to fit about any conspiracy theory with ease.

Or, maybe its just an attempt to increase self-importance? Knowing a deep dark secret of a giant corporation but being unable to tell anyone what it is (while simultaneously telling the world that the secret exists and you know what it is) strikes me as being rather stupid if the secret and fears are real, and as "lookatmeism" if the secret doesn't exist. Either way, you look bad.

Troll.

JazzMan

Reply to
JazzMan

I think JazzMan summed things up pretty well. Bob

Reply to
Bob

"Anthony" wrote

Huh? I doubt anyone that important is browsing these newsgroups looking for people who say negative things about GM. There are no deep, dark, secrets about these pistons and the cold start noise. It's been going on for years, and across many different manufacturers and engines. When I worked for a Chrysler dealership for a few years, we replaced pistons in the Chrysler 3.3 v-6 engine like there was no tomorrow. Same basic design, same basic problems. The manufacturers are finally getting close to the point where the consumer just accepts the fact that their motor will sound like crap for the first five minutes of running.

Ian

Reply to
shiden_kai

"shiden_kai" wrote in news:um82b.23284$ snipped-for-privacy@news2.telusplanet.net:

There is no deep dark secret, you are correct. The reason I am hesitant, is there is the possibility of litigation. The scuffing is a block problem. And you would be suprised at who looks through these newsgroups :).

Reply to
Anthony

"Anthony" wrote

Well, you may be right. I have had my own "pet" theory for years. Ever since we started replacing scuffed pistons on the 3.1 engine in the early Pontiac Transports. What I noticed (it still happens today) is that it was almost always the three front pistons. And it was always the thrust side of those three pistons. I started looking inside the cylinder blocks. As you probably know, the thrust side of the pistons faces the right (rear) side of the block on both banks of pistons. So the rear set (right) of pistons have their thrust side running against the outside of block, and the front set (left) have their thrust sides running against the inside of the block. If you look inside the block, you notice that the coolant passages around the pistons are quite different from the outside to the inside section of the block. Around the outer section of the block, the coolant passage extends to the bottom of the piston sleeves, but on the inner section of the block, the coolant passage doesn't seem to go down as far.

I've speculated that the front bank has it's thrust surface running against the section of the block that doesn't have the water jacket extend as far down the cylinder as it should....perhaps causing excessive heat on that thrust side. The rear bank doesn't have the same problem as it's thrust surfaces are running against a full water jacket all the way down.

But then again, I have seen the occasional motor that has scuffed pistons on the other side...etc. So I'm not ready to say that this is the cause for sure. It's just an educated guess.

The interesting thing is that the 3100 has an actual "scuffing" problem. The pistons are actually "scored". The 2.2 4 cyl engine had the cold piston noise, and so did the Chrysler

3.3 engine. But when you pulled the pistons out on those engines, the pistons were almost never "scuffed". You could plainly see where they were "rocking" into the cylinder wall and causing the cold knock, but they didn't "score" the pistons the way the 3100 does. Which leads me to believe that there probably is some sort of weird design fault in these engines, and GM is just biding their time until they phase them out.

Ian

Reply to
shiden_kai

Sounds reasonable to me.. I remember reading something about how they were using Teflon-coated pistons in the Corvette engines, because the piston-to-bore clearance was built so close that you could actually have negative clearance (interference fit) on the pistons in some cases, and the coating helps prevent the pistons from being scuffed. So it could be that GM is using the teflon-coated pistons in the 3.1s because there's some kind of clearance problem on those engines..

Reply to
Robert Hancock

"Robert Hancock" wrote in news:csB2b.841874$ snipped-for-privacy@news2.calgary.shaw.ca:

It is actually a graphite composite, not teflon.

Reply to
Anthony

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