340 with old Harland S rockers geometry?

I guess if I was in your shoes I would install checker springs on a pair of valves... mark the tips of the valves with some type of marker and see where the "scrub width" is located on the valve. Then take note on the width of the sweep pattern on the valve tips.
This will let you know what's going on and will help Mike at B3 with a starting point.


I'm not a fan of needle bearings. I bought the PRW 1.6 stainless steel rockers in which they are bushed to fit the shafts. No needle bearings. When I received the PRW rockers I read the instructions before taking them out of the box. It spoke of needle bearings. I immediately took a rocker out to make sure they did not have needle bearings.:)

Needle bearings might me better than bushed ... I don't know...but my personal preference is not to run them. Small little part that is subject for failure. If you have been running them since 1975 without problems .... just disregard every word I have said.:D