Quote Originally Posted by Henry Rifle
Matt,

The outside of valve stem boss on the head is machined down so that the seal can slip over it.

I don't understand your question about the difference between dual springs and a single spring.
dual springs are 1 spring within another right? the 1's classic inlines sells are much stiffer than the singles with dampers, allow the same lift tho. so I'm going to get the single springs with dampers, don't need them that much stiffer for turbocharging.