If you are using a custom error 404 page for the missing pages in your site, then it's okay.. However, pages redirected using the error code 404 won't pass any value and won't help your search engine ranking
Yes it depends on what you have set. If there is nothing set and google sees dead links, then it will effect your rankings
a redirected 404 page shouts to google.. "hey im temporarily dead... please knock on my coffin later...."