Quote:
burbank997 said:
It appears that 993 heads are good for about 100 miles and the the valves are shot! Why? Air cooling.


That is not the case. The 993 can suffer from early valve guide failure due to poor quality valve guides being used. They used a material that was ill-fitting and not robust. The valves and heads themselves show no such early wear. It is not a heat-related phenomenon.

When these motors receive aftermarket valve guides, they can run for over two hundred thousand miles...