What's wrong with the GM engine UOA...

Messages
577
Location
Quebec Canada
I've read that often here " your oil analysis shows good number, specialy the wear numbers for a GM engine " Gm wearing faster or what ??? Geez I've seen lots of GM engine with lots of milleage [Confused]
 
Messages
33,976
Location
Southern NJ
I can see where those comments can be misleading. No, not at all. It's the nature of their engines. A GM showing high wear is a normal thing for those engines. GM's engines (some of them) will last a very long time. There are explanations on here that get into it. I don't personally know but bc they show high metals doesn't mean they wear out anymore then any other engine. In fact there is someone with a C5 1999 Corvette with 317,000 miles on it!
 
Messages
52
Location
Poquoson, VA.
quote:
Originally posted by buster: [QBIn fact there is someone with a C5 1999 Corvette with 317,000 miles on it! [/QB]
You gotta be kidding! I dont know anybody that drives a Corvette daily. Most are garage queens. 317000 miles is unreal, especially for the LS1 series engine.
 

Patman

Staff member
Messages
21,989
Location
Oakville, Ontario
quote:
Originally posted by RobWest:
quote:
Originally posted by buster: In fact there is someone with a C5 1999 Corvette with 317,000 miles on it!
You gotta be kidding! I dont know anybody that drives a Corvette daily. Most are garage queens. 317000 miles is unreal, especially for the LS1 series engine.

This guy who owns that car even lives in Michigan! He's a salesman who is on the road all day long and just puts on Goodyear runflat snow tires in the winter and continues to drive unless there is more than about 8" of snow on the ground. He changes his oil every 5000 miles (far too often given his type of driving) with M1 5w30. The LS1 is a very durable engine actually, there are many of them out there now with over 100k on them and still run very strong. They've only been out since 97 in the Corvette, and 98 in the F-body, so in a few more years we'll start seeing more of them with over 200k on them. I'm getting a C5 Corvette in about 3 years and fully expect to get at least 400,000km out of it's original engine before it needs rebuilding.
 
Messages
742
Location
Lake Anna, VA
We have a local doctor who drives his Vette everyday everywhere come hell or high water. He currently owns a 2000 Millenium Yellow C5 Auto. His previous Vette was a early 90's LT1 that had 218,000 miles when he sold it in 2000 for the LS1.
 

Patman

Staff member
Messages
21,989
Location
Oakville, Ontario
quote:
Originally posted by RobWest: So either you get an LS1 with piston slap or one that lasts forever? LOL
There is no evidence which suggests the piston slappers don't last long though. I know a lot of guys who complain about piston slap, but don't know any of them who have needed an engine rebuild yet. The only LS1 owners in my car club that I know who have needed their LS1s rebuilt were those guys who did aftermarket heads and cam packages to their cars, and in those cases I suspect the engine builder just didn't put everything together properly (since both of these guys I know went to the same engine builder)
 
Messages
1,533
Location
Ephraim
quote:
Originally posted by Baveux: -*-* Gm wearing faster or what ??? Geez I've seen lots of GM engine with lots of milleage [Confused]
My opinion is that it's all relative to the nature of the environment AND design AND materials within the engine. I think that ALL engines, if designed without a flaw, have "X" amount of life in them. Now, if every engine has "X" life in them, it's up to the envirenment / oil / maintenance / etc. given to it to extend it's life. My point, is I think every TYPE of engine has its own signature of WEAR metals just because it has different metalic parts in different quantity. Then, I also think every motor within the engine TYPE, has its own wear levels, although close. It's the SECOND or the individual motors wear that we need to TREND. There's already a so called "standard" of known wear metal levels that is BAD, no matter what engine youre in, but it needs refinement and adjustment etc, to get the MOST useful life. This is what I mean: "X" life would be if for instance we changed the oil every 500 miles or 1K or whatever. Anything OVER this number decreases the life of the motor, albeit VERY VERY little. Naturally "driving" conditions affect the issue and so does Quality of oil, and so does OCI. So, IMO as long as OIL burn is low, and oil is fairly clean (????), then it doesn't matter what the numbers are, as long as it doesn't go OUT of the TREND. But what if it does? And what happens if after say 300K or 350K or 400K or whatever the number, the motor shows signs of faster wear? Say two or three times before. If it starts wearing faster, but "well within" a good range, is this GOOD still, and is this the new trend? If this does happen, WHEN should it happen, at what mile ? And if this does happen, does this mean the motor is at "Z"% (????) of its useful life? Anyway, these are some of my vast things I think about EVERY DAY while working, it helps pass the time.
 
Messages
9,448
Location
USA
Patman just be real picky. Try to get an LS1 that does not knock on start up. To date the ones that do not knock have had the best UOA. I am hard on GM engines but I have gone on record as saying that this engine could be world class! I am only hard on them because they could have built a much better engine. THe engine is so darn close to being a great engine it is just a shame that they stoped just short of perfection! Seeing how the Gen III is in everything that uses a V8 and does not have a NS in it it just seems like they could have afforded to get it right the first time! I have no doubt that these engines can last 200,000 baring the extreme piston slappers. We all know that pistons should not rock in their bore allowing the crown to ride the bore. They have experminted with various fix's because it is a problem. It is stupid and shorrt sited to let this whole oil consuption and knock issue persist. This engine is supposed to be good for the next 12-20 years (doubtful). If GM was smart they would add some deck height and push those rings down some. They would add some skirt to the piston and be done with this! [ January 11, 2004, 04:47 PM: Message edited by: JohnBrowning ]
 
Messages
2,768
Location
Tn
John Browning, what do you think of my 3.8L V-6 (GM). They seem to be pretty reliable and what would you run in it?? Anything I should avoid??
 
Messages
9,448
Location
USA
10W30 is fine unless I planed on seeing temps below -25. I have run as thick as 15W40 in my 3.8 dureing the sumer and it loved it. Up until recently the only oil recomended for the 3800 was 10W30. It has just been recently that they went to 5W30 for non super charged units while the super charged 3.8 still recomends 10W30. Mobil 1, Amsoil, Chevron Supreme ,Delo and Delvac have all worked fine in my engine. THe 3.8 is the most reliable engine GM has. THe only real weak spot is the upper intake manifold. I am hopeing that current production has been fixed! If I was redesigning this engine I would make the intake mateing horizontal and it would be made from aluminum. I would give it OHC heads and variable valve timeing! I would not touch anything else. I thionk the transmissions behind these engines need more work then the engines do. I will only 3.8V6's currently. I will not own any other 6 cylinder GM makes for a car!
 
Messages
2,768
Location
Tn
Thanks John Bowning. I am not a big fan of Exxon by any stretch, but this car does seem to like M1 10-30 a lot. I am just trying it and I don't see the super thin reputation.
 

Patman

Staff member
Messages
21,989
Location
Oakville, Ontario
quote:
Originally posted by JohnBrowning: Patman just be real picky. Try to get an LS1 that does not knock on start up.
Believe me, when I go looking for a Corvette, I'll be listening very closely to the engine on startup to see if it has piston slap. Even if the engine can still last long, it's a noise that I could not live with day in and day out, especially since the Corvette I do buy will be my daily driver. I went insane when I owned the 94 Grand Am GT which had a piston slapping 3.1 engine.
 

Patman

Staff member
Messages
21,989
Location
Oakville, Ontario
quote:
Originally posted by buster: Piston slapping has no effect on wear from what I've read. Regardless of the high wear they show, they do last. [Wink]
True, but the noise is guaranteed to send you to the looney bin! [Smile]
 
Messages
3,542
Location
Colorado
My LS1 slaps and it showed some of the lowest wear on here for LS1's. Next UOA will be even better! This "piston slap" in the LS1 design has not even been pin-pointed 100% yet so we can't even say for sure if it is even the pistons making the noise.
 
Messages
2,095
Location
IL
Cris, what about the photos of the truck engine on the pistonslap website? Seems to show bore scuffing to me. Wouldn't that confirm piston slap.
 
Messages
3,542
Location
Colorado
Jason, I have seen those pictures and they do not look good! I have read several other articals on this PS problem on line and there are many other ideas as to what might be causing the noise. Recently we talked on here about the possibility the "diesel sound" might be cause by the oil pump cavatating and causing this problem. Engines are so complex and have so many moving parts it is hare to pin point the problems. I'm sure the pistons caues PS in some engines but other parts could be causing it in other engines. [Frown]
 
Messages
319
Location
N. Florida, USA
quote:
Originally posted by JohnBrowning: It is stupid and shorrt sited to let this whole oil consuption and knock issue persist. This engine is supposed to be good for the next 12-20 years (doubtful). If GM was smart they would add some deck height and push those rings down some. They would add some skirt to the piston and be done with this!
agreed it is seams stupid that GM has not fixed it but I think they went to the short light weight piston to save gas, the government requires a certain average gas mileage from the fleet of cars sold (27.5 MPG, I don't know the light truck average) the consumers want power and safety. a fuel efficient little light weight car with a small engine gives neither, that puts a lot of pressure of the engineers to make compromises and piston mass is where a lot of energy is lost small changes in weight will make perceivable changes in power and efficiency my 8.1L has bad slap and has since 250 miles (few days after purchase) and oil consumption keeps is getting worse. I have not ruled out other possible causes of oil consumption yet but a portion is going past the rings weather it is all or just some I do not know In my opinion the consumer should have the final say in how efficient their car should be, let the manufacturer make the car consumer want, many people will be willing to drive a small no guts car to save $ at the pump but that should be their choice, not the governments
 
Messages
9,448
Location
USA
I was looking at a Z06 piston and Rod assembly that had less then 250 mile on it the other day. From the side it looked like a Hockey Puck with a rod comeing out of it! Their was no skirt at all. THe Buick 3.8 has a real piston skirt and the Olds 3.5 has a decent skirt. On the other hand the 3.1 and 3.4 have very little skirt compared to the above two engines. This current piston design is not going to do a thing for GM. So far it has driven consummer away from GM. Piston slap is widely understood to be bad for durability. The trick is to prove it hurs planed durability. If GM only planes for it to last 150,000 miles and most of them do then they can claim it is not a durability issue. It does not matter that to them that you truck consumes oil at some insane rate after waranty is over! They do not care if it knocks badly. The only way they will fix it is if consumer vote with their walllets or if 60 minutes did something on it! They have used a piston design better suited to an F1 car then a daily driver. The difference though is that they are not useing material that would come close to F1 spec. They are not holding tolerance to this level either. Wear metal is wear metal. These engines can not have higher wear metal in UOA and have less wear. While we do not have any type of set database that would indicate life expectency based on UOA wear metals it is safe to say that the lower an engines wear metal numbers the slower it is wearing out!
 
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