Redirecting affects indexing

[Airco]

I have an old established site that i do not use but ranks high with certain keywords in google. Now I want to use that benefit for another site. If I optimize that other site for the keywords that are on the first one and I let the old site redirect to the new one, what consequences will this have?
And what happens if I load the newer page in a frame on the old domain?

[Delivos]

Loading in frames is an old spammer trick and really breaks the URL bar, I'd say avoid it like the plague - though if you're building MFA then help yourself!

You should be fine for a while, until the engines catch on that content has changed. What's on the established site at the moment? It may well be the case that good incoming links are the power behind your high rankings, and those links will carry on after you redirect the site.