For the 98-2002 style why does the SS have more power than the z-28? What motor mods did they do to make 15 more hp than the z-28?

 

It really does not have any more power than the Z, it was a marketing gimmick to help justify the cost increase on the SS package. I have dynoed enough LS1 to know that pretty much all LS1's will make about the same power.

 

so then what is the stock hp of a z28 and a ss

 

Don't pay any attention to what the advertised hp numbers are, they are not accruite. Just know that any LS1 will put down about 300 rwhp bone stock.