I have taken them to 4.600 on more occasions then I can remember. I wouldn't go over 4.560 on a salt water block since you have to worry about corrosion from the back side of the cylinders. If you are going to go to 4.600, then you have to sonic test the block to check for core shift. I can count on one hand how many I have seen that won't go to 4.600.
With that being said, I didn't choose to go straight to 4.600. I only did it because we had to. Now, I will not hesitate to take one straight to 4.560, and do with most all of them to unshroud the valves with aftermarket, big valve heads. That makes a 524 with a 4" crank and a 555 ci with a 4.25" crank. I have literally done hundreds of them since that block hit the market. It's still a good idea to have it sonic tested. You really need a minimum of .250 wall thickness at least.
I know a few drag racers the have taken them to 4.625. I wouldn't do it, but it has been done. And they didn't fill the block.
Good luck.
Eddie

well seems like conflicting info here also lol. i am wiating for more info, if it is a clean bore at 60 over i am gonna go for it, if there are issues then its a no go. i have been looking for a affordable 502 block for over a year and a half, they are not easy to come by and i do not have pockets deep enough to spend 1800+ on a new one. thanks for the info guys :)

I'm running 4.565 and pushing 650+ hp, no problems. I had a reputable engine builder check the block before and after, no issues.

The operative words here are inspection and testing! Inspection of the existing condition of the block and importantly the conditions of the internal water jackets with respect to rusting and deterioration is critical along with the sonic thickness testing. Even core shift in new cast blocks can lead to bore wall thickness issues and believe me when I say in casting there are no always right blocks that make it to market!
Our new 675HP upgrade for the HP525efi engine is based on a 540 cubic inch with a 4.530 bore and that seems to be a safe place on the average 502 Gen 6 block especially since these are freshwater closed cooled engines. We have as many other builders gone to 4.560 -4.600 on these blocks on many occasions but only after careful inspection and sonic testing. Depending on how long of service life you will expect from the block and how many times you expect to freshen the bores will also be a determiner as you will need addtional material in the bore for re-bores in the future so starting at 4.500-4.530 has some addtional advantages at starting there especially when you consider the cost of a replacement or new core block.
Just some addtional builder advice here.

Best Regards,
Ray @ Raylar

How far can you cut down the decks?.. :party-smiley-004:

We don't cut them as much in the North as they do down south!!:evilb:

I have bored many genVI blocks to 4.560 and boosted them with 10 to 12 lbs of boost with no problems. Rob

4.600

this is one of those cases that ray go savaged over in an earlier post. yes , the info is conflicting but you have two guys that have built more motors sucessfully than the rest of this board combined, telling you the answer.

so, really, what is the question ? is another 20 or 30 thousandths of bore with the associated few cubic inches gain worth introducing variables that will involve a lot of work and effort and expense to check for and even when you are done, you will be taking a substantial risk for absolutely no gain what so ever.

i have said it before and i say it again now. the difference between professionals and home builders is not what that they know what to do , it is that they know what NOT to do.

two of the best professionals in the industry have told you what not to do.

believe them

wow dude?? did you not read all of this or what? the block is already at 60 over, i am not trying to gain cubes! i want a usable block for a mild stroker build. and the pros just said they have taken it 60 over so i am not really sure why you are hammering me?? pretty sure the deal has gone south anyways