To be honest the 400 kinda scares me with the steam holes and such, also why the head gasket let go. He claims it was due to not retorqueing and I do trust him. Back when it was built they never had permatorque gaskets. I found these on ebay. what is the benefit of these pistons over stock?
Speed PRO Chevy 350 5 7 5 7L LT1 Hypereutectic Coated Skirt Piston SET 8 STD | eBay
those are the newer LT1 350 from the 90's
the original LT1 350 was forged pistons.. and made by TRW.. and are a heavy piston..
the newer type are Hypereutectic , it's cast with a higher silicon amount.. think of them as the mid grade (cast/hyper/forged)
they are most likely a lot lighter than the forged trw's
hypers are good pistons as long as nos isn't in it's future and you never get into detonation. they don't break/melt they shatter..
many put a limit of 100-125 hit of happy gas... 150 tops and that's guys that know what they are doing, many have gone even more but they are not new at that game..
the coating,, think of it like your Teflon pans, non stick coating..
they are standard bore... so before I bought these what is in the 350 now..??
as far as the 400 goes.. a straight edge across the deck of block and heads,and feeler gauges will tell the tale there.. (straight across, then corner to corner(the long way), then across the other corner to corner (the long way)
it could be nothing,, easy enough to find out..