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Purchased 2 engines and trying to determine what the differences are. Both engine blocks have the same casting numbers, 1 is a full digit number while the other only has half of the numbers. Also the pistons are different, one is dished while the other is dished with a cross. Any input on these? Pictures included. Thanks!
Both are 5.3l Engines, the second is one that got the little Salvage Yard button on it and it's fallen off from the looks.
Is there any reasoning for the different pistons? Or would that just be a different plant using different pistons. When searrching for cam bearings it’s specifying it’s for a first generation block or a 2nd/3rd generation block. That’s my confusion at this point.
Nobody seems to know why the pistons are different. There was a thread on here about that not long ago. Seems like some motors have ones with and others without. Doesn't seem to be any rhyme or reason. Maybe 2 different suppliers the factory used. There's no significant difference, other than appearance, between them, as far as anybody can tell.
The Pistons changed ever so slightly over the years. I think there was at least 4 versions just in the 99-07 classic GMT 800 series trucks with the Iron blocks. They also switched manufactures through the production.
The early pistons had no coating on the pistons. I believe around 01 they switched manufactures. Around 03 they started adding a coating to the skirt to quiet the motors from the piston slap issue. for the 05 model they went to a floating pin design and beefier rod.
I don't know How many Laptops ago it was but I had posted pictures showing the difference between the 2 manufactures of the pistons and there maker marks. I don't know if I still have any early pistons any more. I doubt I can find the pictures, but I will keep an eye out.
I found the post I made showing the 2 versions of the early pistons with no coating. You can see one casting has the cross marks in the dish while the other one is smooth. https://ls1tech.com/forums/generatio...l#post19417757
I believe the one on the left in the image is the first design. I believe 99-00. The second design is on the right. I believe 01-02. The third should have coated skirts and be 03-04. In 2005 they went to the floating pins with the stronger rods.
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5.3 Engine block identification 
