Tracing grandfather's line

My mother's maiden name in the US was spelled Kasierski. All I know from information I have is that they emmigrated to the USA around 1891 from Posan. I cannot find any immigration info in US because I think the spelling of the last name is not what it was in Poland.
Stephen Kasierski m. Maria Wacoviak around 1866
Children born in Poland: Michael 1867, William 1873, Walenty 1875,
Clementina1877, Frank 1882 and Martin (my great grandfather) 1883.

Martin m. Eva Nowacki in Webster, Masschusetts in 1905

Anyone who may have a correct spelling or an info on this family, please let me know.

Wacoviak - sholuld be Wacowiak in Polish; the other names seems to be correct.

Or Wachowiak?

my grandfather changed our names to wacoviak to walcoby
im not gravedigging i just found this on google

Have you checked the census records? They will give you an idea of what years to search for immigration records. My polish ancestors ended up in Webster also but I do not recognize your surnames.