What was the usage before? What type of lifters? Maybe they were running or planning to run solids? That would be the only reason I could figure. The 942 is the sprAng I'm running on Vixen's engine right now with solids, of course. I set the head up myself and did use shims. I got the seat pressure right in the 130 range. You have to be careful though, because those springs don't have a big range and can't stand a lot of lift. That's why I had to have this cam ground with a low lift, but a FAT duration. It's only .465 lift, but 250 @ .050 duration. It's worked out very well, though, and has the reliability of a stock type camshaft with little stress on the valve train. What lift do you plan on running?