[Walt Fricke]

Las Vegas

I am confused when you ask what 911 valve sizes are, and then think you have found a norm of 46/38.

Here are sizes as the engines got larger from 1965-1989 for the pre-964 stock (not race) engines:

39/35; 42/38; 45/39; 46/40; 49/41.5, per Wayne's 911 engine book.

The last is for the 3.0 and 3.2, whose heads I bet Chris is planning to use. He doesn't specify an intake valve diameter to start this discussion, but says he is looking at 41mm exhausts, where I am guessing he meant 41.5.

The 964 is 49/42.5, and the 993 is 49/43, then 50/43.5 with the Varioram, per Frere. After that Porsche went with water cooling and 4 valve heads.

Walt