What's the valve stem diameter on a Hemi? 5/16"
G3 Hemi? 8mm, IIRC.
Racers have been using 5/16 or 8mm stems to save weight on valves for 30 years or more.

NASCAR type motors are running 7mm and even I've heard of some 6mm stems, that's pretty doggone small, makes me wonder. But IMHO as long as you're replacing guides, go to a common smaller size, and that's 5/16 or 8mm.


R.