Stage 4 head 420a

[inferno617]

I took my head to the local machine shop and asked if he could work with it becuase i was unsure of it condition and its great just needs a line bore. I need to know the specs for a stage 4 head so I can have him port it and do a valve job. I am looking to put in over size +1mm valves. If anyone can help me that would be great.

 

[inferno617]

I also need to know how well SBI is. I am looking at using them for my valves, valve keepers, lifters, rocker arms and guides