What is the advantage of a double valve spring vs just a single spring? I'm looking at these LT4 springs for my 383. I have yet to determine if they will fit in my spring pockets but I will do that yet tonight. My camshaft is a factory LT4 roller cam(which these springs match, and they can go higher lift if I wanted). For about $50 I can get a set of valve springs that look about perfect for my application.