I agree. But you absolutely "must" find out what rings were used! The 5.3 rings will fit on a 6.2 piston, but there would be at least a 30 thousandths ring gap and that is unacceptably excessive, and noticeable. 4 thousandths per inch bore gap is the acceptable industry maximum (and some is absolutely needed for ring heat expansion), so about 16 thousandths would be your maximum. 5.3 rings would be twice that from the get go.
There is no way that if you had a 5.3 to use 6.2 rings. The pistons could never fit back in because the rings would never compress enough to slide the pistons back into the cylinders.
I won't say the 5.3 rings won't work - at least in the short term. But if they were used, I would anticipate excessive engine blowby, lowered compression, higher fuel usage, higher oil usage, and lowered performance later on with their use as wear increases their gap even more.
It is not my intent to scare you, but to give you information to relay to your engine rebuilder that you know what you are talking about. Ask for their invoice for your rings. They should be happy to show you if they used the correct parts. I truly hope they did.
Monday, November 30th, 2020 AT 2:55 PM