MyE28.com

I'm in the process of rebuilding a head for my turbo build & am curious if someone could compare and contrast the stock b34 valve springs against the double b35 valve springs. Advantages/disadvantages of either? Also does anyone know the difference in spring rates?

No disadvantage. I turned b35 valve springs to 7200 in first gear at the dragstrip. 6800 all other times. 6600 for the b34 springs.

If I remember correctly from my hot-rodding days: Dual spring first came to use to help prevent the phenomena of valve bounce off the seats caused by harmonics of the springs and the use of high lift cams. The dual springs harmonics canceled out each other and helped prevent the bounce. Of course there a few other advantages like increased spring rates (Which can be way over done), etc. I think for moderate cams the single springs would work fine. I would just use what ever the stock head came with, new of course. Now rockers themselves are more problematic.

I replaced my springs with metric mechanic 2 piece, and the rockers with ireland engineering heavy duty rockers. I can now rev to 7k, before it felt weak past 5k,and I kept breaking rockers.
marc