question on Valve spring/roller rocker install??

[a1yola]

I am installing a set of GT40 heads on my car. I am also going to use 1.7 Crane Cams roller rockers from a cobra. When I put piston #1 at TDC, I bolted the rockers down to zero lash. Then I torqued them down to 20 ft/lbs. I noticed that the valve springs compressed slightly. So I tried using the stock rockers (from my non-GT40 heads) and it did the same thing.

I know that when changing to roller rockers, I will need to use shims, but why would the springs compress even with the stock rockers?? From my understanding, there shouldnt be any type of spring compression when at TDC, right? What shuld I do when installing the 1.7 RR's??


Thanks!

 

[SwAmPf0x]

You may need shims, its not just zero lash then 20 ft/lbs, you need to count how far the bolt turns to reach 20, should be 1/4 to 1 full turn, more and you need shims, less you need longer pushrods