I have measured my valve stems with an installed height micrometer and the total height on the intake is 1.820 and 1.900 on the exhaust.

My springs are rated at 130 lbs. at 1.800" so this is the approximate installed height I'm shooting for.

On the intake I used one .030" shim and came up with an installed height of 1.7825". Not Bad right.

On the exhaust I stacked a .060", a .030" and a .015" and ended up with an installed height of 1.8025". Again, not bad.

My concern now is that when I use these shims there is not much left of the spring pocket depth. The heads are Chevy 081 (LB9) castings. There is just a very small amount of casting material that rises high enough to help locate the springs. Should I be concerned about the bottoms of the springs shifting back and forth?

 

You'll be ok. its the inner diameter of the valve guide boss that locates the spring, not the outer diameter of the spring pocket. just recheck you installed heights and you're good to go.

 

If you've done some guide machining and/or are using single springs, you always have the option of spring cups.

 

There has not been any machining of the guides. I'm using a single spring with a damper. I am not familiar with spring cups. would they install under or over the springs?

BTW, thanks for your replies.