When I mill the 54/55 year cylinder heads .090" to get the same compression ratio as an 848 head, I shim the rocker shaft stands up 3/32" to retain the same intake valve geometry, and use a lash cap on the exhaust valve stems. The intake valves need to be recessed into the head the same .090 dimension to shroud the edge of the valves from the combustion flame, or the valves will burn quickly. Works like a champ!
Jerry
