valve spring Q

[blesi660r]

I got a question, are valve springs a swap in and go kinda thing, was told today that they might need shimming? for an exstra 50 bucks I can pick up some Brian crowers with titanium retainers, lots of mixed feelings with the evo springs on dsmtuners also talked with aa buddy and was surprised to find that he ran 280s on stock springs. Kinda getting mixed reviews, but all in all I really appreciate all the help and tips guys thank you.