21-01-2020, 11:55 AM
A spectrum of views to be expected here. I wouldn't advocate modifying original parts when there is a range of good aftermarket ones available (some of which look a lot like original or at least contemporary heads; some are classics in their own right). Most are aluminium mainly because it's lighter and better for cooling. The minor(?) downside of aluminium heads is they are easier to warp. Personally I follow Bill Williams' advice and wouldn't run a compression ratio above 6.5 or so on a car I aspired to get home in, not unless it had some bottom-end enhancement anyway. Fastest head I ever ran personally was a Speedex, but at 10:1 or so CR I figured the fun wouldn't last, have mostly used a standard cast iron '37 head since.