Info on LS1/LS6, piston slap, oil use, relates to 4.6

It looks like GM has not completely fixed the oil use issue on the LS1/LS6 (at least up to 2001; 2002 engines use a newer coated piston).
Interesting info from "the other side", and how it may relate to piston slap theories for the Ford 4.6 modular. It would appear that piston slap goes hand in hand with oil use; anyone here with the engine rattle problem seeing oil use?

BTW, here are links to C5 piston/head where 1 quart was being burned in just under 2000 miles (you'll find the post below interesting where he claims 1 quart in 1200 miles is OK):

http://www.brightland.com/c5/head/head1.jpg
http://www.brightland.com/c5/head/oilcarbonpistons.jpg

Here's the article from http://forums.corvetteforum.com/zerothread?id=224983 :


Hi,
Let me give it to you from the Horse's mouth so of speak. David F just stopped by to say hello. I will have him answer your question below:
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Let me see if I can help answer your question. First the new rings are to help reduce oil use. It does not claim to stop it. If you are able to get a hold of a copy of the GM bulletin it states that it is to help bring oil use to an acceptable level and it can be helped with a change in driving style. The problem heppens when the RPM are kept above 3,200 for extended piriods of time. This is why it's common with stick cars and not autos. Now there was a concern that some of the 01s may have been built with defective lifter valley covers so that may have to be looked at also. The problem is that in order to build HP and get fuel mileage GM has gone with lighter and smaller pistons and use rings with very low tension. The problem with this is that the pistons can move around in the cylinder a lot more. I've talked with an engine builder here in the Atlanta area (works with GM) and he agrees that the oil use problem can not be fixed, he also adds that it has something to do with ring flutter at high RPMs too. He said even if he were to go with a good aftermarket piston and rings the problem would still be there; maybe a little better but it would still use oil. I also know of another engine builder down in Florida. He has friends in high places at GM that has contacted them in order to help a friend out with an 01 with oil consumption problems and was told by people at GM that there was no fix and were not working on any at that time. He even re-contacted them telling them how they would be able to fix the problem but was told they were not interested.
Now with all this said let me get back to a few things no in reference to the 02s they are using a coated piston, Why? So they are able to reduce piston to bore clearances. Why? To help reduce piston slap when the engine is cold. How would that help? With reduced clearances the piston will not move as much, but just reducing piston to bore clearances will only make it possible that the piston could score the cylinder wall, so they coat the pistons to help with this. It's because of the different expansion rates of the piston vs. cylinder walls that the clearences have to be larger than we would like. Now it could be that because of the reduced piston to cylinder clearance that the 02 has not had as many complaints as the 01, but also keep in mind that I think all or just about all 02s came with the new style rings(really it's only the lower compression ring that is different) and they also have made sure that no defective lifter valley covers are installed. Remember all that is different to the lower compression ring is on the bottom out side. They have machined a grove that acts like an oil scrapper to help keep oil down from the top ring and there by keep it from being burned.
The way the LS6 is built is not unlike many aftermarket engines are being built today. Today engines are being built loose, so it takes less HP to turn the engine which means more of the turning of the engine can be put towards making HP. Many of the new engines that are able to rev high built in the aftermarket are noisy when cold and use oil, I just don't think it can be done any other way unless extreme care is used in every step of the engine build and even then if the engine is kept in the high RPMs it will use oil.
I feel if you are getting over 1,200 miles per quart of oil you are doing fine, yes there are always going to be some cars out there that will do better but they may not make as much power, we have tested a car that had a serve case of oil use, it was bought back by GM and before it was send to the auction. I installed the revised rings after the installation the car was tested. 60mph to 100mph and tested HP and the car was fast, very fast as fast if not faster than any 02 tested and HP came in at 427, so there is something to be said about a loose engine.
I don't know if any of this helps, but the point I do want to make is a Z06 if driven to have fun will use some oil, and if you can't accept it for the way it is then you will not be happy with the car or just about any high performance car made today. I just don't know anything else to say. Just keep an eye on your oil and enjoy the car it is one very fast car, maybe even the best balanced car ever!

David Fulcher


<font size=-1>[ This Message was edited by: DrivingSimulators on 2002-02-04 02:53 ]</font>