DRAM has it right, more info is needed.
On my current race motor with a 4.375" bore, hardblock, and other factors; I decided to put the top ring at 0.021", and the second ring at 0.024". I have used tighter in the past with less hp.

1993 Daytona, 5.50 at 130mph (1/8) 1.19 sixty ft (PG). Link to 572 B1 - Part 1