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I am working on a LC9 engine and need to replace one piston. I looked the part up by the vin number and the GM catalog only provides one part number for a flat top piston for anything in the 4th gen LS. As you can see in the pictures, it is different near the bottom but everything else is identical as far as dimensions. I cannot get a clear answer if this would be fine to run along with the other design and if this was just a design change along the way. Sorry if this has been answered before I have been searching without any luck finding answers. Thanks everybody
It's just strange that I can find no part number anywhere for the stock pistons I have. Everywhere I see used ones for sale they are the same shape as my old ones, but if you try to find a new one that design its like it doesn't exist. I see a few gen 3 pistons that look like that but are press in pins. Just kind of mind boggling. Anybody have a part number for the old ones? The part number listed for the vin is 89060486 and has not been changed, but its obviously not what came in the vehicle.
It's just strange that I can find no part number anywhere for the stock pistons I have. Everywhere I see used ones for sale they are the same shape as my old ones, but if you try to find a new one that design its like it doesn't exist. I see a few gen 3 pistons that look like that but are press in pins. Just kind of mind boggling. Anybody have a part number for the old ones? The part number listed for the vin is 89060486 and has not been changed, but its obviously not what came in the vehicle.
I would call your favorite local GM dealer and have them look the part up. The online catalogs are notorious for being inaccurate.
I work at a dealer and called gm myself after having no luck in the catalog. I searched by the vin from my engine first then looked at every other model of vehicle that uses a 4th gen Ls and any of the flat top pistons only show this part number with no engineering notes or record of a number change. I've searched the service end of things in SI for bulletins or recalls maybe noting a change in design for any reason and no luck there either. I have never had an issue with any part information like this. Denmah has a pic on the sloppy wiki of gen 3 and gen 4 rods comparing them and my stock pistons look exactly like gen 3 pistons but they aren't pressed in pins. Going to weigh them tonight and see what I come up with
GM also had a service bulletin to replace the pistons, rings, windage tray, valley cover, etc. for oil consumption issues. I had this performed under warranty on my 2008 Avalanch 5.3 non-Flex Fuel. Maybe the only piston available is the "new design".
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Gen IV LC9 piston skirt difference 
