I just got a set of old titanium valves and they are 5/16 stem diameter. Is the stock ls1 head stem diameter 5/16 or 8.5mm? also I was wondering how big you can take the stock valve seats to? any info would be great.

 

"Old titanium valves" are a euphamism for "a grenade with the pin pulled". The LS* engine family uses 8mm stem valves (.314") and 5/16" generally measure .311" (unless you have some Hemi valves = .309" stems). Either way, unless you change the valve guide to a smaller inside dia. you will be left with significant stem to guide clearances (.0015"-.002" are ideal). Also, titanium does not make for a reliable exhaust valve. The valve heads tend to fall off after extended use. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> The stock seat inserts are around 2.035" for intake and 1.585" exhaust and so there isn't much steel left for seating valves with stock sized seats. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />
Hope this helps,
Richard <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />